HTTP Live Streaming 2nd Edition
draft-pantos-hls-rfc8216bis-00
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draft-pantos-hls-rfc8216bis-00
Informational R. Pantos, Ed.
Internet-Draft Apple Inc.
Obsoletes: 8216 (if approved) December 8, 2017
Intended status: Informational
Expires: June 11, 2018
HTTP Live Streaming 2nd Edition
draft-pantos-hls-rfc8216bis-00
Abstract
This document obsoletes RFC 8216. It describes a protocol for
transferring unbounded streams of multimedia data. It specifies the
data format of the files and the actions to be taken by the server
(sender) and the clients (receivers) of the streams. It describes
version 8 of this protocol.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 11, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
This document may not be modified, and derivative works of it may not
be created, except to format it for publication as an RFC or to
translate it into languages other than English.
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This Informational Internet Draft is submitted as an RFC Editor
Contribution and/or non-IETF Document (not as a Contribution, IETF
Contribution, nor IETF Document) in accordance with BCP 78 and BCP
79.
Table of Contents
1. Introduction to HTTP Live Streaming . . . . . . . . . . . . . 4
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Media Segments . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Supported Media Segment Formats . . . . . . . . . . . . . 6
3.2. MPEG-2 Transport Streams . . . . . . . . . . . . . . . . 7
3.3. Fragmented MPEG-4 . . . . . . . . . . . . . . . . . . . . 7
3.4. Packed Audio . . . . . . . . . . . . . . . . . . . . . . 8
3.5. WebVTT . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6. IMSC Subtitles . . . . . . . . . . . . . . . . . . . . . 9
4. Playlists . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Definition of a Playlist . . . . . . . . . . . . . . . . 10
4.2. Attribute Lists . . . . . . . . . . . . . . . . . . . . . 11
4.3. Variable Substitution . . . . . . . . . . . . . . . . . . 12
4.4. Playlist Tags . . . . . . . . . . . . . . . . . . . . . . 12
4.4.1. Basic Tags . . . . . . . . . . . . . . . . . . . . . 13
4.4.1.1. EXTM3U . . . . . . . . . . . . . . . . . . . . . 13
4.4.1.2. EXT-X-VERSION . . . . . . . . . . . . . . . . . . 13
4.4.2. Media Segment Tags . . . . . . . . . . . . . . . . . 13
4.4.2.1. EXTINF . . . . . . . . . . . . . . . . . . . . . 14
4.4.2.2. EXT-X-BYTERANGE . . . . . . . . . . . . . . . . . 14
4.4.2.3. EXT-X-DISCONTINUITY . . . . . . . . . . . . . . . 15
4.4.2.4. EXT-X-KEY . . . . . . . . . . . . . . . . . . . . 15
4.4.2.5. EXT-X-MAP . . . . . . . . . . . . . . . . . . . . 17
4.4.2.6. EXT-X-PROGRAM-DATE-TIME . . . . . . . . . . . . . 18
4.4.2.7. EXT-X-DATERANGE . . . . . . . . . . . . . . . . . 18
4.4.2.7.1. Mapping SCTE-35 into EXT-X-DATERANGE . . . . 20
4.4.2.8. EXT-X-GAP . . . . . . . . . . . . . . . . . . . . 22
4.4.3. Media Playlist Tags . . . . . . . . . . . . . . . . . 22
4.4.3.1. EXT-X-TARGETDURATION . . . . . . . . . . . . . . 23
4.4.3.2. EXT-X-MEDIA-SEQUENCE . . . . . . . . . . . . . . 23
4.4.3.3. EXT-X-DISCONTINUITY-SEQUENCE . . . . . . . . . . 23
4.4.3.4. EXT-X-ENDLIST . . . . . . . . . . . . . . . . . . 24
4.4.3.5. EXT-X-PLAYLIST-TYPE . . . . . . . . . . . . . . . 24
4.4.3.6. EXT-X-I-FRAMES-ONLY . . . . . . . . . . . . . . . 25
4.4.4. Master Playlist Tags . . . . . . . . . . . . . . . . 25
4.4.4.1. EXT-X-MEDIA . . . . . . . . . . . . . . . . . . . 26
4.4.4.1.1. Rendition Groups . . . . . . . . . . . . . . 29
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4.4.4.2. EXT-X-STREAM-INF . . . . . . . . . . . . . . . . 29
4.4.4.2.1. Alternative Renditions . . . . . . . . . . . 33
4.4.4.3. EXT-X-I-FRAME-STREAM-INF . . . . . . . . . . . . 34
4.4.4.4. EXT-X-SESSION-DATA . . . . . . . . . . . . . . . 35
4.4.4.5. EXT-X-SESSION-KEY . . . . . . . . . . . . . . . . 36
4.4.5. Media or Master Playlist Tags . . . . . . . . . . . . 36
4.4.5.1. EXT-X-INDEPENDENT-SEGMENTS . . . . . . . . . . . 36
4.4.5.2. EXT-X-START . . . . . . . . . . . . . . . . . . . 37
4.4.5.3. EXT-X-DEFINE . . . . . . . . . . . . . . . . . . 38
5. Key Files . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.1. Structure of Key Files . . . . . . . . . . . . . . . . . 39
5.2. IV for AES-128 . . . . . . . . . . . . . . . . . . . . . 39
6. Client/Server Responsibilities . . . . . . . . . . . . . . . 39
6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 39
6.2. Server Responsibilities . . . . . . . . . . . . . . . . . 39
6.2.1. General Server Responsibilities . . . . . . . . . . . 39
6.2.2. Live Playlists . . . . . . . . . . . . . . . . . . . 42
6.2.3. Encrypting Media Segments . . . . . . . . . . . . . . 43
6.2.4. Providing Variant Streams . . . . . . . . . . . . . . 44
6.3. Client Responsibilities . . . . . . . . . . . . . . . . . 45
6.3.1. General Client Responsibilities . . . . . . . . . . . 45
6.3.2. Loading the Media Playlist File . . . . . . . . . . . 46
6.3.3. Playing the Media Playlist File . . . . . . . . . . . 47
6.3.4. Reloading the Media Playlist File . . . . . . . . . . 48
6.3.5. Determining the Next Segment to Load . . . . . . . . 49
6.3.6. Decrypting Encrypted Media Segments . . . . . . . . . 50
7. Protocol Version Compatibility . . . . . . . . . . . . . . . 51
8. Playlist Examples . . . . . . . . . . . . . . . . . . . . . . 52
8.1. Simple Media Playlist . . . . . . . . . . . . . . . . . . 52
8.2. Live Media Playlist Using HTTPS . . . . . . . . . . . . . 52
8.3. Playlist with Encrypted Media Segments . . . . . . . . . 53
8.4. Master Playlist . . . . . . . . . . . . . . . . . . . . . 53
8.5. Master Playlist with I-Frames . . . . . . . . . . . . . . 53
8.6. Master Playlist with Alternative Audio . . . . . . . . . 54
8.7. Master Playlist with Alternative Video . . . . . . . . . 54
8.8. Session Data in a Master Playlist . . . . . . . . . . . . 55
8.9. CHARACTERISTICS Attribute Containing Multiple
Characteristics . . . . . . . . . . . . . . . . . . . . . 55
8.10. EXT-X-DATERANGE Carrying SCTE-35 Tags . . . . . . . . . . 56
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 56
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 56
11. Security Considerations . . . . . . . . . . . . . . . . . . . 57
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 58
12.1. Normative References . . . . . . . . . . . . . . . . . . 58
12.2. Informative References . . . . . . . . . . . . . . . . . 62
Appendix A. Changes from RFC 8216 . . . . . . . . . . . . . . . 63
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 63
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1. Introduction to HTTP Live Streaming
HTTP Live Streaming provides a reliable, cost-effective means of
delivering continuous and long-form video over the Internet. It
allows a receiver to adapt the bit rate of the media to the current
network conditions in order to maintain uninterrupted playback at the
best possible quality. It supports interstitial content boundaries.
It provides a flexible framework for media encryption. It can
efficiently offer multiple renditions of the same content, such as
audio translations. It offers compatibility with large-scale HTTP
caching infrastructure to support delivery to large audiences.
Since its first draft publication in 2009, HTTP Live Streaming has
been implemented and deployed by a wide array of content producers,
tools vendors, distributors, and device manufacturers. In the
subsequent eight years the protocol has been refined by extensive
review and discussion with a variety of media streaming implementors.
The purpose of this document is to facilitate interoperability
between HTTP Live Streaming implementations by describing the media
transmission protocol. Using this protocol, a client can receive a
continuous stream of media from a server for concurrent presentation.
This document describes version 8 of the protocol.
2. Overview
A multimedia presentation is specified by a Uniform Resource
Identifier (URI) [RFC3986] to a Playlist.
A Playlist is either a Media Playlist or a Master Playlist. Both are
UTF-8 text files containing URIs and descriptive tags.
A Media Playlist contains a list of Media Segments, which, when
played sequentially, will play the multimedia presentation.
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Here is an example of a Media Playlist:
#EXTM3U
#EXT-X-TARGETDURATION:10
#EXTINF:9.009,
http://media.example.com/first.ts
#EXTINF:9.009,
http://media.example.com/second.ts
#EXTINF:3.003,
http://media.example.com/third.ts
The first line is the format identifier tag #EXTM3U. The line
containing #EXT-X-TARGETDURATION says that all Media Segments will be
10 seconds long or less. Then, three Media Segments are declared.
The first and second are 9.009 seconds long; the third is 3.003
seconds.
To play this Playlist, the client first downloads it and then
downloads and plays each Media Segment declared within it. The
client reloads the Playlist as described in this document to discover
any added segments. Data SHOULD be carried over HTTP [RFC7230], but,
in general, a URI can specify any protocol that can reliably transfer
the specified resource on demand.
A more complex presentation can be described by a Master Playlist. A
Master Playlist provides a set of Variant Streams, each of which
describes a different version of the same content.
A Variant Stream includes a Media Playlist that specifies media
encoded at a particular bit rate, in a particular format, and at a
particular resolution for media containing video.
A Variant Stream can also specify a set of Renditions. Renditions
are alternate versions of the content, such as audio produced in
different languages or video recorded from different camera angles.
Clients should switch between different Variant Streams to adapt to
network conditions. Clients should choose Renditions based on user
preferences.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. Media Segments
A Media Playlist contains a series of Media Segments that make up the
overall presentation. A Media Segment is specified by a URI and
optionally a byte range.
The duration of each Media Segment is indicated in the Media Playlist
by its EXTINF tag (Section 4.4.2.1).
Each segment in a Media Playlist has a unique integer Media Sequence
Number. The Media Sequence Number of the first segment in the Media
Playlist is either 0 or declared in the Playlist (Section 4.4.3.2).
The Media Sequence Number of every other segment is equal to the
Media Sequence Number of the segment that precedes it plus one.
Each Media Segment MUST carry the continuation of the encoded
bitstream from the end of the segment with the previous Media
Sequence Number, where values in a series such as timestamps and
Continuity Counters MUST continue uninterrupted. The only exceptions
are the first Media Segment ever to appear in a Media Playlist and
Media Segments that are explicitly signaled as discontinuities
(Section 4.4.2.3). Unmarked media discontinuities can trigger
playback errors.
Any Media Segment that contains video SHOULD include enough
information to initialize a video decoder and decode a continuous set
of frames that includes the final frame in the Segment; network
efficiency is optimized if there is enough information in the Segment
to decode all frames in the Segment. For example, any Media Segment
containing H.264 video SHOULD contain an Instantaneous Decoding
Refresh (IDR); frames prior to the first IDR will be downloaded but
possibly discarded.
3.1. Supported Media Segment Formats
All Media Segments MUST be in a format described in this section.
Transport of other media file formats is not defined.
Some media formats require a common sequence of bytes to initialize a
parser before a Media Segment can be parsed. This format-specific
sequence is called the Media Initialization Section. The Media
Initialization Section can be specified by an EXT-X-MAP tag
(Section 4.4.2.5). The Media Initialization Section MUST NOT contain
sample data.
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3.2. MPEG-2 Transport Streams
MPEG-2 Transport Streams are specified by [ISO_13818].
The Media Initialization Section of an MPEG-2 Transport Stream
Segment is a Program Association Table (PAT) followed by a Program
Map Table (PMT).
Transport Stream Segments MUST contain a single MPEG-2 Program;
playback of Multi-Program Transport Streams is not defined. Each
Transport Stream Segment MUST contain a PAT and a PMT, or have an
EXT-X-MAP tag (Section 4.4.2.5) applied to it. The first two
Transport Stream packets in a Segment without an EXT-X-MAP tag SHOULD
be a PAT and a PMT.
3.3. Fragmented MPEG-4
MPEG-4 Fragments are specified by the ISO Base Media File Format
[ISOBMFF]. Unlike regular MPEG-4 files that have a Movie Box
('moov') that contains sample tables and a Media Data Box ('mdat')
containing the corresponding samples, an MPEG-4 Fragment consists of
a Movie Fragment Box ('moof') containing a subset of the sample table
and a Media Data Box containing those samples. Use of MPEG-4
Fragments does require a Movie Box for initialization, but that Movie
Box contains only non-sample-specific information such as track and
sample descriptions.
A Fragmented MPEG-4 (fMP4) Segment is a "segment" as defined by
Section 3 of [ISOBMFF], including the constraints on Media Data Boxes
in Section 8.16 of [ISOBMFF].
The Media Initialization Section for an fMP4 Segment is an ISO Base
Media File that can initialize a parser for that Segment.
Broadly speaking, fMP4 Segments and Media Initialization Sections are
[ISOBMFF] files that also satisfy the constraints described in this
section.
The Media Initialization Section for an fMP4 Segment MUST contain a
File Type Box ('ftyp') containing a brand that is compatible with
'iso6' or higher. The File Type Box MUST be followed by a Movie Box.
The Movie Box MUST contain a Track Box ('trak') for every Track
Fragment Box ('traf') in the fMP4 Segment, with matching track_ID.
Each Track Box SHOULD contain a sample table, but its sample count
MUST be zero. Movie Header Boxes ('mvhd') and Track Header Boxes
('tkhd') MUST have durations of zero. A Movie Extends Box ('mvex')
MUST follow the last Track Box. Note that a Common Media Application
Format [CMAF] Header meets all these requirements.
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In an fMP4 Segment, every Track Fragment Box MUST contain a Track
Fragment Decode Time Box ('tfdt'). fMP4 Segments MUST use movie-
fragment-relative addressing. fMP4 Segments MUST NOT use external
data references. Note that a CMAF Segment meets these requirements.
An fMP4 Segment in a Playlist containing the EXT-X-I-FRAMES-ONLY tag
(Section 4.4.3.6) MAY omit the portion of the Media Data Box
following the intra-coded frame (I-frame) sample data.
Each fMP4 Segment in a Media Playlist MUST have an EXT-X-MAP tag
applied to it.
3.4. Packed Audio
A Packed Audio Segment contains encoded audio samples and ID3 tags
that are simply packed together with minimal framing and no per-
sample timestamps. Supported Packed Audio formats are Advanced Audio
Coding (AAC) with Audio Data Transport Stream (ADTS) framing
[ISO_13818_7], MP3 [ISO_13818_3], AC-3 [AC_3], and Enhanced AC-3
[AC_3].
A Packed Audio Segment has no Media Initialization Section.
Each Packed Audio Segment MUST signal the timestamp of its first
sample with an ID3 Private frame (PRIV) tag [ID3] at the beginning of
the segment. The ID3 PRIV owner identifier MUST be
"com.apple.streaming.transportStreamTimestamp". The ID3 payload MUST
be a 33-bit MPEG-2 Program Elementary Stream timestamp expressed as a
big-endian eight-octet number, with the upper 31 bits set to zero.
Clients SHOULD NOT play Packed Audio Segments without this ID3 tag.
3.5. WebVTT
A WebVTT Segment is a section of a WebVTT [WebVTT] file. WebVTT
Segments carry subtitles.
The Media Initialization Section of a WebVTT Segment is the WebVTT
header.
Each WebVTT Segment MUST contain all subtitle cues that are intended
to be displayed during the period indicated by the segment EXTINF
duration. The start time offset and end time offset of each cue MUST
indicate the total display time for that cue, even if part of the cue
time range is outside the Segment period. A WebVTT Segment MAY
contain no cues; this indicates that no subtitles are to be displayed
during that period.
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Each WebVTT Segment MUST either start with a WebVTT header or have an
EXT-X-MAP tag applied to it.
In order to synchronize timestamps between audio/video and subtitles,
an X-TIMESTAMP-MAP metadata header SHOULD be added to each WebVTT
header. This header maps WebVTT cue timestamps to MPEG-2 (PES)
timestamps in other Renditions of the Variant Stream. Its format is:
X-TIMESTAMP-MAP=LOCAL:<cue time>,MPEGTS:<MPEG-2 time>
e.g., X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
The cue timestamp in the LOCAL attribute MAY fall outside the range
of time covered by the segment.
If a WebVTT segment does not have the X-TIMESTAMP-MAP, the client
MUST assume that the WebVTT cue time of 0 maps to an MPEG-2 timestamp
of 0.
When synchronizing WebVTT with PES timestamps, clients SHOULD account
for cases where the 33-bit PES timestamps have wrapped and the WebVTT
cue times have not.
3.6. IMSC Subtitles
An IMSC Segment is a Fragmented MPEG-4 (Section 3.3) Media Segment
that carries subtitle media according to MPEG-4 Part 30
[MP4_TIMED_TEXT]. This subtitle media MUST comply with the Text
Profile of IMSC1 [IMSC1].
The Media Initialization Section of an IMSC Segment is specified in
Section 3.3.
Each IMSC Segment MUST contain all subtitle samples that are intended
to be displayed during the period indicated by the segment EXTINF
duration. Each Segment MUST contain definitions for all styles which
are applied to any part of any sample in the Segment.
4. Playlists
This section describes the Playlist files used by HTTP Live
Streaming. In this section, "MUST" and "MUST NOT" specify the rules
for the syntax and structure of legal Playlist files. Playlists that
violate these rules are invalid; clients MUST fail to parse them.
See Section 6.3.2.
The format of the Playlist files is derived from the M3U [M3U]
playlist file format and inherits two tags from that earlier file
format: EXTM3U (Section 4.4.1.1) and EXTINF (Section 4.4.2.1).
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In the specification of tag syntax, a string enclosed by <>
identifies a tag parameter; its specific format is described in its
tag definition. If a parameter is further surrounded by [], it is
optional; otherwise, it is required.
Each Playlist file MUST be identifiable either by the path component
of its URI or by HTTP Content-Type. In the first case, the path MUST
end with either .m3u8 or .m3u. In the second, the HTTP Content-Type
MUST be "application/vnd.apple.mpegurl" or "audio/mpegurl". Clients
SHOULD refuse to parse Playlists that are not so identified.
4.1. Definition of a Playlist
Playlist files MUST be encoded in UTF-8 [RFC3629]. They MUST NOT
contain any Byte Order Mark (BOM); clients SHOULD fail to parse
Playlists that contain a BOM or do not parse as UTF-8. Playlist
files MUST NOT contain UTF-8 control characters (U+0000 to U+001F and
U+007F to U+009F), with the exceptions of CR (U+000D) and LF
(U+000A). All character sequences MUST be normalized according to
Unicode normalization form "NFC" [UNICODE]. Note that US-ASCII
[US_ASCII] conforms to these rules.
Lines in a Playlist file are terminated by either a single line feed
character or a carriage return character followed by a line feed
character. Each line is a URI, is blank, or starts with the
character '#'. Blank lines are ignored. Whitespace MUST NOT be
present, except for elements in which it is explicitly specified.
Lines that start with the character '#' are either comments or tags.
Tags begin with #EXT. They are case sensitive. All other lines that
begin with '#' are comments and SHOULD be ignored.
A URI line identifies a Media Segment or a Playlist file (see
Section 4.4.4.2). Each Media Segment is specified by a URI and the
tags that apply to it.
A Playlist is a Media Playlist if all URI lines in the Playlist
identify Media Segments. A Playlist is a Master Playlist if all URI
lines in the Playlist identify Media Playlists. A Playlist MUST be
either a Media Playlist or a Master Playlist; all other Playlists are
invalid.
A URI in a Playlist, whether it is a URI line or part of a tag, MAY
be relative. Any relative URI is considered to be relative to the
URI of the Playlist that contains it.
The duration of a Media Playlist is the sum of the durations of the
Media Segments within it.
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The segment bit rate of a Media Segment is the size of the Media
Segment divided by its EXTINF duration (Section 4.4.2.1). Note that
this includes container overhead but does not include overhead
imposed by the delivery system, such as HTTP, TCP, or IP headers.
The peak segment bit rate of a Media Playlist is the largest bit rate
of any contiguous set of segments whose total duration is between 0.5
and 1.5 times the target duration. The bit rate of a set is
calculated by dividing the sum of the segment sizes by the sum of the
segment durations.
The average segment bit rate of a Media Playlist is the sum of the
sizes (in bits) of every Media Segment in the Media Playlist, divided
by the Media Playlist duration. Note that this includes container
overhead, but not HTTP or other overhead imposed by the delivery
system.
4.2. Attribute Lists
Certain tags have values that are attribute-lists. An attribute-list
is a comma-separated list of attribute/value pairs with no
whitespace.
An attribute/value pair has the following syntax:
AttributeName=AttributeValue
An AttributeName is an unquoted string containing characters from the
set [A..Z], [0..9], and '-'. Therefore, AttributeNames contain only
uppercase letters, not lowercase. There MUST NOT be any whitespace
between the AttributeName and the '=' character, nor between the '='
character and the AttributeValue.
An AttributeValue is one of the following:
o decimal-integer: an unquoted string of characters from the set
[0..9] expressing an integer in base-10 arithmetic in the range
from 0 to 2^64-1 (18446744073709551615). A decimal-integer may be
from 1 to 20 characters long.
o hexadecimal-sequence: an unquoted string of characters from the
set [0..9] and [A..F] that is prefixed with 0x or 0X. The maximum
length of a hexadecimal-sequence depends on its AttributeNames.
o decimal-floating-point: an unquoted string of characters from the
set [0..9] and '.' that expresses a non-negative floating-point
number in decimal positional notation.
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o signed-decimal-floating-point: an unquoted string of characters
from the set [0..9], '-', and '.' that expresses a signed
floating-point number in decimal positional notation.
o quoted-string: a string of characters within a pair of double
quotes (0x22). The following characters MUST NOT appear in a
quoted-string: line feed (0xA), carriage return (0xD), or double
quote (0x22). Quoted-string AttributeValues SHOULD be constructed
so that byte-wise comparison is sufficient to test two quoted-
string AttributeValues for equality. Note that this implies case-
sensitive comparison.
o enumerated-string: an unquoted character string from a set that is
explicitly defined by the AttributeName. An enumerated-string
will never contain double quotes ("), commas (,), or whitespace.
o decimal-resolution: two decimal-integers separated by the "x"
character. The first integer is a horizontal pixel dimension
(width); the second is a vertical pixel dimension (height).
The type of the AttributeValue for a given AttributeName is specified
by the attribute definition.
A given AttributeName MUST NOT appear more than once in a given
attribute-list. Clients SHOULD refuse to parse such Playlists.
4.3. Variable Substitution
The following Playlist elements are subject to variable substitution:
o URI lines
o quoted-string AttributeValues
o hexadecimal-sequence AttributeValues
A Variable Reference is a string of the form "{$" (0x7B,0x24)
followed by a Variable Name followed by "}" (0x7D). Variable Names
are defined by the EXT-X-DEFINE tag (Section 4.4.5.3).
See Section 6.3.1 for more information about variable substitution.
4.4. Playlist Tags
Playlist tags specify either global parameters of the Playlist or
information about the Media Segments or Media Playlists that appear
after them.
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4.4.1. Basic Tags
These tags are allowed in both Media Playlists and Master Playlists.
4.4.1.1. EXTM3U
The EXTM3U tag indicates that the file is an Extended M3U [M3U]
Playlist file. It MUST be the first line of every Media Playlist and
every Master Playlist. Its format is:
#EXTM3U
4.4.1.2. EXT-X-VERSION
The EXT-X-VERSION tag indicates the compatibility version of the
Playlist file, its associated media, and its server.
The EXT-X-VERSION tag applies to the entire Playlist file. Its
format is:
#EXT-X-VERSION:<n>
where n is an integer indicating the protocol compatibility version
number.
It MUST appear in all Playlists containing tags or attributes that
are not compatible with protocol version 1 to support
interoperability with older clients. Section 7 specifies the minimum
value of the compatibility version number for any given Playlist
file.
A Playlist file MUST NOT contain more than one EXT-X-VERSION tag. If
a client encounters a Playlist with multiple EXT-X-VERSION tags, it
MUST fail to parse it.
4.4.2. Media Segment Tags
Each Media Segment is specified by a series of Media Segment tags
followed by a URI. Some Media Segment tags apply to just the next
segment; others apply to all subsequent segments until another
instance of the same tag.
A Media Segment tag MUST NOT appear in a Master Playlist. Clients
MUST fail to parse Playlists that contain both Media Segment tags and
Master Playlist tags (Section 4.4.4).
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4.4.2.1. EXTINF
The EXTINF tag specifies the duration of a Media Segment. It applies
only to the next Media Segment. This tag is REQUIRED for each Media
Segment. Its format is:
#EXTINF:<duration>,[<title>]
where duration is a decimal-floating-point or decimal-integer number
(as described in Section 4.2) that specifies the duration of the
Media Segment in seconds. Durations SHOULD be decimal-floating-
point, with enough accuracy to avoid perceptible error when segment
durations are accumulated. However, if the compatibility version
number is less than 3, durations MUST be integers. Durations that
are reported as integers SHOULD be rounded to the nearest integer.
The remainder of the line following the comma is an optional human-
readable informative title of the Media Segment expressed as UTF-8
text.
4.4.2.2. EXT-X-BYTERANGE
The EXT-X-BYTERANGE tag indicates that a Media Segment is a sub-range
of the resource identified by its URI. It applies only to the next
URI line that follows it in the Playlist. Its format is:
#EXT-X-BYTERANGE:<n>[@<o>]
where n is a decimal-integer indicating the length of the sub-range
in bytes. If present, o is a decimal-integer indicating the start of
the sub-range, as a byte offset from the beginning of the resource.
If o is not present, the sub-range begins at the next byte following
the sub-range of the previous Media Segment.
If o is not present, a previous Media Segment MUST appear in the
Playlist file and MUST be a sub-range of the same media resource, or
the Media Segment is undefined and the client MUST fail to parse the
Playlist.
A Media Segment without an EXT-X-BYTERANGE tag consists of the entire
resource identified by its URI.
Use of the EXT-X-BYTERANGE tag REQUIRES a compatibility version
number of 4 or greater.
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4.4.2.3. EXT-X-DISCONTINUITY
The EXT-X-DISCONTINUITY tag indicates a discontinuity between the
Media Segment that follows it and the one that preceded it.
Its format is:
#EXT-X-DISCONTINUITY
The EXT-X-DISCONTINUITY tag MUST be present if there is a change in
any of the following characteristics:
o file format
o number, type, and identifiers of tracks
o timestamp sequence
The EXT-X-DISCONTINUITY tag SHOULD be present if there is a change in
any of the following characteristics:
o encoding parameters
o encoding sequence
See Section 3, Section 6.2.1, and Section 6.3.3 for more information
about the EXT-X-DISCONTINUITY tag.
4.4.2.4. EXT-X-KEY
Media Segments MAY be encrypted. The EXT-X-KEY tag specifies how to
decrypt them. It applies to every Media Segment and to every Media
Initialization Section declared by an EXT-X-MAP tag that appears
between it and the next EXT-X-KEY tag in the Playlist file with the
same KEYFORMAT attribute (or the end of the Playlist file). Two or
more EXT-X-KEY tags with different KEYFORMAT attributes MAY apply to
the same Media Segment if they ultimately produce the same decryption
key. The format is:
#EXT-X-KEY:<attribute-list>
The following attributes are defined:
METHOD
The value is an enumerated-string that specifies the encryption
method. This attribute is REQUIRED.
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The methods defined are: NONE, AES-128, and SAMPLE-AES.
An encryption method of NONE means that Media Segments are not
encrypted. If the encryption method is NONE, other attributes
MUST NOT be present.
An encryption method of AES-128 signals that Media Segments are
completely encrypted using the Advanced Encryption Standard (AES)
[AES_128] with a 128-bit key, Cipher Block Chaining (CBC), and
Public-Key Cryptography Standards #7 (PKCS7) padding [RFC5652].
CBC is restarted on each segment boundary, using either the
Initialization Vector (IV) attribute value or the Media Sequence
Number as the IV; see Section 5.2.
An alternative to whole-segment encryption is Sample Encryption.
With Sample Encryption, only media sample data - such as audio
packets or video frames - is encrypted. The rest of the Media
Segment is unencrypted. Sample Encryption allows parts of the
Segment to be processed without (or before) decrypting the media
itself.
An encryption method of SAMPLE-AES means that the Media Segments
are Sample Encrypted using the Advanced Encryption Standard
[AES_128]. How these media streams are encrypted and encapsulated
in a segment depends on the media encoding and the media format of
the segment. fMP4 Media Segments are encrypted using the 'cbcs'
scheme of Common Encryption [COMMON_ENC]. Encryption of other
Media Segment formats containing H.264 [H_264], AAC [ISO_14496],
AC-3 [AC_3], and Enhanced AC-3 [AC_3] media streams is described
in the HTTP Live Streaming (HLS) Sample Encryption specification
[SampleEnc]. The IV attribute MAY be present; see Section 5.2.
URI
The value is a quoted-string containing a URI that specifies how
to obtain the key. This attribute is REQUIRED unless the METHOD
is NONE.
IV
The value is a hexadecimal-sequence that specifies a 128-bit
unsigned integer Initialization Vector to be used with the key.
Use of the IV attribute REQUIRES a compatibility version number of
2 or greater. See Section 5.2 for when the IV attribute is used.
KEYFORMAT
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The value is a quoted-string that specifies how the key is
represented in the resource identified by the URI; see Section 5
for more detail. This attribute is OPTIONAL; its absence
indicates an implicit value of "identity". Use of the KEYFORMAT
attribute REQUIRES a compatibility version number of 5 or greater.
KEYFORMATVERSIONS
The value is a quoted-string containing one or more positive
integers separated by the "/" character (for example, "1", "1/2",
or "1/2/5"). If more than one version of a particular KEYFORMAT
is defined, this attribute can be used to indicate which
version(s) this instance complies with. This attribute is
OPTIONAL; if it is not present, its value is considered to be "1".
Use of the KEYFORMATVERSIONS attribute REQUIRES a compatibility
version number of 5 or greater.
If the Media Playlist file does not contain an EXT-X-KEY tag, then
Media Segments are not encrypted.
See Section 5 for the format of the Key file, and Section 5.2,
Section 6.2.3, and Section 6.3.6 for additional information on Media
Segment encryption.
4.4.2.5. EXT-X-MAP
The EXT-X-MAP tag specifies how to obtain the Media Initialization
Section (Section 3) required to parse the applicable Media Segments.
It applies to every Media Segment that appears after it in the
Playlist until the next EXT-X-MAP tag or until the end of the
Playlist.
Its format is:
#EXT-X-MAP:<attribute-list>
The following attributes are defined:
URI
The value is a quoted-string containing a URI that identifies a
resource that contains the Media Initialization Section. This
attribute is REQUIRED.
BYTERANGE
The value is a quoted-string specifying a byte range into the
resource identified by the URI attribute. This range SHOULD
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contain only the Media Initialization Section. The format of the
byte range is described in Section 4.4.2.2. This attribute is
OPTIONAL; if it is not present, the byte range is the entire
resource indicated by the URI.
An EXT-X-MAP tag SHOULD be supplied for Media Segments in Playlists
with the EXT-X-I-FRAMES-ONLY tag when the first Media Segment (i.e.,
I-frame) in the Playlist (or the first segment following an EXT-
X-DISCONTINUITY tag) does not immediately follow the Media
Initialization Section at the beginning of its resource.
Use of the EXT-X-MAP tag in a Media Playlist that contains the EXT-
X-I-FRAMES-ONLY tag REQUIRES a compatibility version number of 5 or
greater. Use of the EXT-X-MAP tag in a Media Playlist that DOES NOT
contain the EXT-X-I-FRAMES-ONLY tag REQUIRES a compatibility version
number of 6 or greater.
If the Media Initialization Section declared by an EXT-X-MAP tag is
encrypted with a METHOD of AES-128, the IV attribute of the EXT-X-KEY
tag that applies to the EXT-X-MAP is REQUIRED.
4.4.2.6. EXT-X-PROGRAM-DATE-TIME
The EXT-X-PROGRAM-DATE-TIME tag associates the first sample of a
Media Segment with an absolute date and/or time. It applies only to
the next Media Segment. Its format is:
#EXT-X-PROGRAM-DATE-TIME:<date-time-msec>
where date-time-msec is an ISO/IEC 8601:2004 [ISO_8601] date/time
representation, such as YYYY-MM-DDThh:mm:ss.SSSZ. It SHOULD indicate
a time zone and fractional parts of seconds, to millisecond accuracy.
For example:
#EXT-X-PROGRAM-DATE-TIME:2010-02-19T14:54:23.031+08:00
See Section 6.2.1 and Section 6.3.3 for more information on the EXT-
X-PROGRAM-DATE-TIME tag.
4.4.2.7. EXT-X-DATERANGE
The EXT-X-DATERANGE tag associates a Date Range (i.e., a range of
time defined by a starting and ending date) with a set of attribute/
value pairs. Its format is:
#EXT-X-DATERANGE:<attribute-list>
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where the defined attributes are:
ID
A quoted-string that uniquely identifies a Date Range in the
Playlist. This attribute is REQUIRED.
CLASS
A client-defined quoted-string that specifies some set of
attributes and their associated value semantics. All Date Ranges
with the same CLASS attribute value MUST adhere to these
semantics. This attribute is OPTIONAL.
START-DATE
A quoted-string containing the ISO-8601 date at which the Date
Range begins. This attribute is REQUIRED.
END-DATE
A quoted-string containing the ISO-8601 date at which the Date
Range ends. It MUST be equal to or later than the value of the
START-DATE attribute. This attribute is OPTIONAL.
DURATION
The duration of the Date Range expressed as a decimal-floating-
point number of seconds. It MUST NOT be negative. A single
instant in time (e.g., crossing a finish line) SHOULD be
represented with a duration of 0. This attribute is OPTIONAL.
PLANNED-DURATION
The expected duration of the Date Range expressed as a decimal-
floating-point number of seconds. It MUST NOT be negative. This
attribute SHOULD be used to indicate the expected duration of a
Date Range whose actual duration is not yet known. It is
OPTIONAL.
X-<client-attribute>
The "X-" prefix defines a namespace reserved for client-defined
attributes. The client-attribute MUST be a legal AttributeName.
Clients SHOULD use a reverse-DNS syntax when defining their own
attribute names to avoid collisions. The attribute value MUST be
a quoted-string, a hexadecimal-sequence, or a decimal-floating-
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point. An example of a client-defined attribute is X-COM-EXAMPLE-
AD-ID="XYZ123". These attributes are OPTIONAL.
SCTE35-CMD, SCTE35-OUT, SCTE35-IN
Used to carry SCTE-35 data; see Section 4.4.2.7.1 for more
information. These attributes are OPTIONAL.
END-ON-NEXT
An enumerated-string whose value MUST be YES. This attribute
indicates that the end of the range containing it is equal to the
START-DATE of its Following Range. The Following Range is the
Date Range of the same CLASS that has the earliest START-DATE
after the START-DATE of the range in question. This attribute is
OPTIONAL.
An EXT-X-DATERANGE tag with an END-ON-NEXT=YES attribute MUST have a
CLASS attribute. Other EXT-X-DATERANGE tags with the same CLASS
attribute MUST NOT specify Date Ranges that overlap.
An EXT-X-DATERANGE tag with an END-ON-NEXT=YES attribute MUST NOT
contain DURATION or END-DATE attributes.
A Date Range with neither a DURATION, an END-DATE, nor an END-ON-
NEXT=YES attribute has an unknown duration, even if it has a PLANNED-
DURATION.
If a Playlist contains an EXT-X-DATERANGE tag, it MUST also contain
at least one EXT-X-PROGRAM-DATE-TIME tag.
If a Playlist contains two EXT-X-DATERANGE tags with the same ID
attribute value, then any AttributeName that appears in both tags
MUST have the same AttributeValue.
If a Date Range contains both a DURATION attribute and an END-DATE
attribute, the value of the END-DATE attribute MUST be equal to the
value of the START-DATE attribute plus the value of the DURATION
attribute.
Clients SHOULD ignore EXT-X-DATERANGE tags with illegal syntax.
4.4.2.7.1. Mapping SCTE-35 into EXT-X-DATERANGE
Splice information carried in source media according to the SCTE-35
specification [SCTE35] MAY be represented in a Media Playlist using
EXT-X-DATERANGE tags.
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Each SCTE-35 splice_info_section() containing a splice_null(),
splice_schedule(), bandwidth_reservation(), or private_cmd() SHOULD
be represented by an EXT-X-DATERANGE tag with an SCTE35-CMD attribute
whose value is the big-endian binary representation of the
splice_info_section(), expressed as a hexadecimal-sequence.
An SCTE-35 splice out/in pair signaled by a pair of splice_insert()
commands SHOULD be represented by one or more EXT-X-DATERANGE tags
carrying the same ID attribute, which MUST be unique to that splice
out/in pair. The "out" splice_info_section() (with
out_of_network_indicator set to 1) MUST be placed in an SCTE35-OUT
attribute, with the same formatting as SCTE35-CMD. The "in"
splice_info_section() (with out_of_network_indicator set to 0) MUST
be placed in an SCTE35-IN attribute, with the same formatting as
SCTE35-CMD.
An SCTE-35 splice out/in pair signaled by a pair of time_signal()
commands, each carrying a single segmentation_descriptor(), SHOULD be
represented by one or more EXT-X-DATERANGE tags carrying the same ID
attribute, which MUST be unique to that splice out/in pair. The
"out" splice_info_section() MUST be placed in an SCTE35-OUT
attribute; the "in" splice_info_section() MUST be placed in an
SCTE35-IN attribute.
Different types of segmentation, as indicated by the
segmentation_type_id in the segmentation_descriptor(), SHOULD be
represented by separate EXT-X-DATERANGE tags, even if two or more
segmentation_descriptor()s arrive in the same splice_info_section().
In that case, each EXT-X-DATERANGE tag will have an SCTE35-OUT,
SCTE35-IN, or SCTE35-CMD attribute whose value is the entire
splice_info_section().
An SCTE-35 time_signal() command that does not signal a splice out or
in point SHOULD be represented by an EXT-X-DATERANGE tag with an
SCTE35-CMD attribute.
The START-DATE of an EXT-X-DATERANGE tag containing an SCTE35-OUT
attribute MUST be the date and time that corresponds to the program
time of that splice.
The START-DATE of an EXT-X-DATERANGE tag containing an SCTE35-CMD
MUST be the date and time specified by the splice_time() in the
command or the program time at which the command appeared in the
source stream if the command does not specify a splice_time().
An EXT-X-DATERANGE tag containing an SCTE35-OUT attribute MAY contain
a PLANNED-DURATION attribute. Its value MUST be the planned duration
of the splice.
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The DURATION of an EXT-X-DATERANGE tag containing an SCTE35-IN
attribute MUST be the actual (not planned) program duration between
the corresponding out-point and that in-point.
The END-DATE of an EXT-X-DATERANGE tag containing an SCTE35-IN
attribute MUST be the actual (not planned) program date and time of
that in-point.
If the actual end date and time is not known when an SCTE35-OUT
attribute is added to the Playlist, the DURATION attribute and the
END-TIME attribute MUST NOT be present; the actual end date of the
splice SHOULD be signaled by another EXT-X-DATERANGE tag once it has
been established.
A canceled splice SHOULD NOT appear in the Playlist as an EXT-
X-DATERANGE tag.
An EXT-X-DATERANGE tag announcing a splice SHOULD be added to a
Playlist at the same time as the last pre-splice Media Segment, or
earlier if possible.
The ID attribute of an EXT-X-DATERANGE tag MAY contain a
splice_event_id and/or a segmentation_event_id, but it MUST be unique
in the Playlist. If there is a possibility that an SCTE-35 id will
be reused, the ID attribute value MUST include disambiguation, such
as a date or sequence number.
4.4.2.8. EXT-X-GAP
The EXT-X-GAP tag indicates that the segment URL to which it applies
does not contain media data and SHOULD NOT be loaded by clients. It
applies only to the next Media Segment.
Its format is:
#EXT-X-GAP
See Section 6.2.1 and Section 6.3.3 for more information on the EXT-
X-GAP tag.
4.4.3. Media Playlist Tags
Media Playlist tags describe global parameters of the Media Playlist.
There MUST NOT be more than one Media Playlist tag of each type in
any Media Playlist.
A Media Playlist tag MUST NOT appear in a Master Playlist
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4.4.3.1. EXT-X-TARGETDURATION
The EXT-X-TARGETDURATION tag specifies the maximum Media Segment
duration. The EXTINF duration of each Media Segment in the Playlist
file, when rounded to the nearest integer, MUST be less than or equal
to the target duration; longer segments can trigger playback stalls
or other errors. It applies to the entire Playlist file. Its format
is:
#EXT-X-TARGETDURATION:<s>
where s is a decimal-integer indicating the target duration in
seconds. The EXT-X-TARGETDURATION tag is REQUIRED.
4.4.3.2. EXT-X-MEDIA-SEQUENCE
The EXT-X-MEDIA-SEQUENCE tag indicates the Media Sequence Number of
the first Media Segment that appears in a Playlist file. Its format
is:
#EXT-X-MEDIA-SEQUENCE:<number>
where number is a decimal-integer.
If the Media Playlist file does not contain an EXT-X-MEDIA-SEQUENCE
tag, then the Media Sequence Number of the first Media Segment in the
Media Playlist SHALL be considered to be 0. A client MUST NOT assume
that segments with the same Media Sequence Number in different Media
Playlists contain matching content (see Section 6.3.2).
A URI for a Media Segment is not required to contain its Media
Sequence Number.
See Section 6.2.1 and Section 6.3.5 for more information on setting
the EXT-X-MEDIA-SEQUENCE tag.
The EXT-X-MEDIA-SEQUENCE tag MUST appear before the first Media
Segment in the Playlist.
4.4.3.3. EXT-X-DISCONTINUITY-SEQUENCE
The EXT-X-DISCONTINUITY-SEQUENCE tag allows synchronization between
different Renditions of the same Variant Stream or different Variant
Streams that have EXT-X-DISCONTINUITY tags in their Media Playlists.
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Its format is:
#EXT-X-DISCONTINUITY-SEQUENCE:<number>
where number is a decimal-integer.
If the Media Playlist does not contain an EXT-X-DISCONTINUITY-
SEQUENCE tag, then the Discontinuity Sequence Number of the first
Media Segment in the Playlist SHALL be considered to be 0.
The EXT-X-DISCONTINUITY-SEQUENCE tag MUST appear before the first
Media Segment in the Playlist.
The EXT-X-DISCONTINUITY-SEQUENCE tag MUST appear before any EXT-
X-DISCONTINUITY tag.
See Section 6.2.1 and Section 6.2.2 for more information about
setting the value of the EXT-X-DISCONTINUITY-SEQUENCE tag.
4.4.3.4. EXT-X-ENDLIST
The EXT-X-ENDLIST tag indicates that no more Media Segments will be
added to the Media Playlist file. It MAY occur anywhere in the Media
Playlist file. Its format is:
#EXT-X-ENDLIST
4.4.3.5. EXT-X-PLAYLIST-TYPE
The EXT-X-PLAYLIST-TYPE tag provides mutability information about the
Media Playlist file. It applies to the entire Media Playlist file.
It is OPTIONAL. Its format is:
#EXT-X-PLAYLIST-TYPE:<type-enum>
where type-enum is either EVENT or VOD.
Section 6.2.1 defines the implications of the EXT-X-PLAYLIST-TYPE
tag.
If the EXT-X-PLAYLIST-TYPE value is EVENT, Media Segments can only be
added to the end of the Media Playlist. If the EXT-X-PLAYLIST-TYPE
value is Video On Demand (VOD), the Media Playlist cannot change.
If the EXT-X-PLAYLIST-TYPE tag is omitted from a Media Playlist, the
Playlist can be updated according to the rules in Section 6.2.1 with
no additional restrictions. For example, a live Playlist
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(Section 6.2.2) MAY be updated to remove Media Segments in the order
that they appeared.
4.4.3.6. EXT-X-I-FRAMES-ONLY
The EXT-X-I-FRAMES-ONLY tag indicates that each Media Segment in the
Playlist describes a single I-frame. I-frames are encoded video
frames whose decoding does not depend on any other frame. I-frame
Playlists can be used for trick play, such as fast forward, rapid
reverse, and scrubbing.
The EXT-X-I-FRAMES-ONLY tag applies to the entire Playlist. Its
format is:
#EXT-X-I-FRAMES-ONLY
In a Playlist with the EXT-X-I-FRAMES-ONLY tag, the Media Segment
duration (EXTINF tag value) is the time between the presentation time
of the I-frame in the Media Segment and the presentation time of the
next I-frame in the Playlist, or the end of the presentation if it is
the last I-frame in the Playlist.
Media resources containing I-frame segments MUST begin with either a
Media Initialization Section (Section 3) or be accompanied by an EXT-
X-MAP tag indicating the Media Initialization Section so that clients
can load and decode I-frame segments in any order. The byte range of
an I-frame segment with an EXT-X-BYTERANGE tag applied to it
(Section 4.4.2.2) MUST NOT include its Media Initialization Section;
clients can assume that the Media Initialization Section is defined
by the EXT-X-MAP tag, or is located between the start of the resource
and the offset of the first I-frame segment in that resource.
Use of the EXT-X-I-FRAMES-ONLY REQUIRES a compatibility version
number of 4 or greater.
4.4.4. Master Playlist Tags
Master Playlist tags define the Variant Streams, Renditions, and
other global parameters of the presentation.
Master Playlist tags MUST NOT appear in a Media Playlist; clients
MUST fail to parse any Playlist that contains both a Master Playlist
tag and either a Media Playlist tag or a Media Segment tag.
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4.4.4.1. EXT-X-MEDIA
The EXT-X-MEDIA tag is used to relate Media Playlists that contain
alternative Renditions (Section 4.4.4.2.1) of the same content. For
example, three EXT-X-MEDIA tags can be used to identify audio-only
Media Playlists that contain English, French, and Spanish Renditions
of the same presentation. Or, two EXT-X-MEDIA tags can be used to
identify video-only Media Playlists that show two different camera
angles.
Its format is:
#EXT-X-MEDIA:<attribute-list>
The following attributes are defined:
TYPE
The value is an enumerated-string; valid strings are AUDIO, VIDEO,
SUBTITLES, and CLOSED-CAPTIONS. This attribute is REQUIRED.
Typically, closed-caption [CEA608] media is carried in the video
stream. Therefore, an EXT-X-MEDIA tag with TYPE of CLOSED-
CAPTIONS does not specify a Rendition; the closed-caption media is
present in the Media Segments of every video Rendition.
URI
The value is a quoted-string containing a URI that identifies the
Media Playlist file. This attribute is OPTIONAL; see
Section 4.4.4.2.1. If the TYPE is CLOSED-CAPTIONS, the URI
attribute MUST NOT be present.
GROUP-ID
The value is a quoted-string that specifies the group to which the
Rendition belongs. See Section 4.4.4.1.1. This attribute is
REQUIRED.
LANGUAGE
The value is a quoted-string containing one of the standard Tags
for Identifying Languages [RFC5646], which identifies the primary
language used in the Rendition. This attribute is OPTIONAL.
ASSOC-LANGUAGE
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The value is a quoted-string containing a language tag [RFC5646]
that identifies a language that is associated with the Rendition.
An associated language is often used in a different role than the
language specified by the LANGUAGE attribute (e.g., written versus
spoken, or a fallback dialect). This attribute is OPTIONAL.
The LANGUAGE and ASSOC-LANGUAGE attributes can be used, for
example, to link Norwegian Renditions that use different spoken
and written languages.
NAME
The value is a quoted-string containing a human-readable
description of the Rendition. If the LANGUAGE attribute is
present, then this description SHOULD be in that language. This
attribute is REQUIRED.
DEFAULT
The value is an enumerated-string; valid strings are YES and NO.
If the value is YES, then the client SHOULD play this Rendition of
the content in the absence of information from the user indicating
a different choice. This attribute is OPTIONAL. Its absence
indicates an implicit value of NO.
AUTOSELECT
The value is an enumerated-string; valid strings are YES and NO.
This attribute is OPTIONAL. Its absence indicates an implicit
value of NO. If the value is YES, then the client MAY choose to
play this Rendition in the absence of explicit user preference
because it matches the current playback environment, such as
chosen system language.
If the AUTOSELECT attribute is present, its value MUST be YES if
the value of the DEFAULT attribute is YES.
FORCED
The value is an enumerated-string; valid strings are YES and NO.
This attribute is OPTIONAL. Its absence indicates an implicit
value of NO. The FORCED attribute MUST NOT be present unless the
TYPE is SUBTITLES.
A value of YES indicates that the Rendition contains content that
is considered essential to play. When selecting a FORCED
Rendition, a client SHOULD choose the one that best matches the
current playback environment (e.g., language).
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A value of NO indicates that the Rendition contains content that
is intended to be played in response to explicit user request.
INSTREAM-ID
The value is a quoted-string that specifies a Rendition within the
segments in the Media Playlist. This attribute is REQUIRED if the
TYPE attribute is CLOSED-CAPTIONS, in which case it MUST have one
of the values: "CC1", "CC2", "CC3", "CC4", or "SERVICEn" where n
MUST be an integer between 1 and 63 (e.g., "SERVICE9" or
"SERVICE42").
The values "CC1", "CC2", "CC3", and "CC4" identify a Line 21 Data
Services channel [CEA608]. The "SERVICE" values identify a
Digital Television Closed Captioning [CEA708] service block
number.
For all other TYPE values, the INSTREAM-ID MUST NOT be specified.
CHARACTERISTICS
The value is a quoted-string containing one or more Uniform Type
Identifiers [UTI] separated by comma (,) characters. This
attribute is OPTIONAL. Each UTI indicates an individual
characteristic of the Rendition.
A SUBTITLES Rendition MAY include the following characteristics:
"public.accessibility.transcribes-spoken-dialog",
"public.accessibility.describes-music-and-sound", and
"public.easy-to-read" (which indicates that the subtitles have
been edited for ease of reading).
An AUDIO Rendition MAY include the following characteristic:
"public.accessibility.describes-video".
The CHARACTERISTICS attribute MAY include private UTIs.
CHANNELS
The value is a quoted-string that specifies an ordered, slash-
separated ("/") list of parameters. If the TYPE attribute is
AUDIO, then the first parameter is a count of audio channels
expressed as a decimal-integer, indicating the maximum number of
independent, simultaneous audio channels present in any Media
Segment in the Rendition. For example, an AC-3 5.1 Rendition
would have a CHANNELS="6" attribute. No other CHANNELS parameters
are currently defined.
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All audio EXT-X-MEDIA tags SHOULD have a CHANNELS attribute. If a
Master Playlist contains two Renditions encoded with the same
codec but a different number of channels, then the CHANNELS
attribute is REQUIRED; otherwise, it is OPTIONAL.
4.4.4.1.1. Rendition Groups
A set of one or more EXT-X-MEDIA tags with the same GROUP-ID value
and the same TYPE value defines a Group of Renditions. Each member
of the Group MUST be an alternative Rendition of the same content;
otherwise, playback errors can occur.
All EXT-X-MEDIA tags in a Playlist MUST meet the following
constraints:
o All EXT-X-MEDIA tags in the same Group MUST have different NAME
attributes.
o A Group MUST NOT have more than one member with a DEFAULT
attribute of YES.
o Each EXT-X-MEDIA tag with an AUTOSELECT=YES attribute SHOULD have
a combination of LANGUAGE [RFC5646], ASSOC-LANGUAGE, FORCED, and
CHARACTERISTICS attributes that is distinct from those of other
AUTOSELECT=YES members of its Group.
A Playlist MAY contain multiple Groups of the same TYPE in order to
provide multiple encodings of that media type. If it does so, each
Group of the same TYPE MUST have the same set of members, and each
corresponding member MUST have identical attributes with the
exception of the URI and CHANNELS attributes.
Each member in a Group of Renditions MAY have a different sample
format. For example, an English Rendition can be encoded with AC-3
5.1 while a Spanish Rendition is encoded with AAC stereo. However,
any EXT-X-STREAM-INF tag (Section 4.4.4.2) or EXT-X-I-FRAME-STREAM-
INF tag (Section 4.4.4.3) that references such a Group MUST have a
CODECS attribute that lists every sample format present in any
Rendition in the Group, or client playback failures can occur. In
the example above, the CODECS attribute would include
"ac-3,mp4a.40.2".
4.4.4.2. EXT-X-STREAM-INF
The EXT-X-STREAM-INF tag specifies a Variant Stream, which is a set
of Renditions that can be combined to play the presentation. The
attributes of the tag provide information about the Variant Stream.
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The URI line that follows the EXT-X-STREAM-INF tag specifies a Media
Playlist that carries a Rendition of the Variant Stream. The URI
line is REQUIRED. Clients that do not support multiple video
Renditions SHOULD play this Rendition.
Its format is:
#EXT-X-STREAM-INF:<attribute-list>
<URI>
The following attributes are defined:
BANDWIDTH
The value is a decimal-integer of bits per second. It represents
the peak segment bit rate of the Variant Stream.
If all the Media Segments in a Variant Stream have already been
created, the BANDWIDTH value MUST be the largest sum of peak
segment bit rates that is produced by any playable combination of
Renditions. (For a Variant Stream with a single Media Playlist,
this is just the peak segment bit rate of that Media Playlist.)
An inaccurate value can cause playback stalls or prevent clients
from playing the variant.
If the Master Playlist is to be made available before all Media
Segments in the presentation have been encoded, the BANDWIDTH
value SHOULD be the BANDWIDTH value of a representative period of
similar content, encoded using the same settings.
Every EXT-X-STREAM-INF tag MUST include the BANDWIDTH attribute.
AVERAGE-BANDWIDTH
The value is a decimal-integer of bits per second. It represents
the average segment bit rate of the Variant Stream.
If all the Media Segments in a Variant Stream have already been
created, the AVERAGE-BANDWIDTH value MUST be the largest sum of
average segment bit rates that is produced by any playable
combination of Renditions. (For a Variant Stream with a single
Media Playlist, this is just the average segment bit rate of that
Media Playlist.) An inaccurate value can cause playback stalls or
prevent clients from playing the variant.
If the Master Playlist is to be made available before all Media
Segments in the presentation have been encoded, the AVERAGE-
BANDWIDTH value SHOULD be the AVERAGE-BANDWIDTH value of a
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representative period of similar content, encoded using the same
settings.
The AVERAGE-BANDWIDTH attribute is OPTIONAL.
CODECS
The value is a quoted-string containing a comma-separated list of
formats, where each format specifies a media sample type that is
present in one or more Renditions specified by the Variant Stream.
Valid format identifiers are those in the ISO Base Media File
Format Name Space defined by "The 'Codecs' and 'Profiles'
Parameters for "Bucket" Media Types" [RFC6381].
For example, a stream containing AAC low complexity (AAC-LC) audio
and H.264 Main Profile Level 3.0 video would have a CODECS value
of "mp4a.40.2,avc1.4d401e".
Note that if a Variant Stream specifies one or more Renditions
that include IMSC subtitles, the CODECS attribute MUST indicate
this with a format identifier such as "stpp.ttml.im1t".
Every EXT-X-STREAM-INF tag SHOULD include a CODECS attribute.
RESOLUTION
The value is a decimal-resolution describing the optimal pixel
resolution at which to display all the video in the Variant
Stream.
The RESOLUTION attribute is OPTIONAL but is recommended if the
Variant Stream includes video.
FRAME-RATE
The value is a decimal-floating-point describing the maximum frame
rate for all the video in the Variant Stream, rounded to three
decimal places.
The FRAME-RATE attribute is OPTIONAL but is recommended if the
Variant Stream includes video. The FRAME-RATE attribute SHOULD be
included if any video in a Variant Stream exceeds 30 frames per
second.
HDCP-LEVEL
The value is an enumerated-string; valid strings are TYPE-0, TYPE-
1, and NONE. This attribute is advisory. A value of TYPE-0
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indicates that the Variant Stream could fail to play unless the
output is protected by High-bandwidth Digital Content Protection
(HDCP) Type 0 [HDCP] or equivalent. A value of TYPE-1 indicates
that the Variant Stream could fail to play unless the output is
protected by HDCP Type 1 or equivalent. A value of NONE indicates
that the content does not require output copy protection.
Encrypted Variant Streams with different HDCP levels SHOULD use
different media encryption keys.
The HDCP-LEVEL attribute is OPTIONAL. It SHOULD be present if any
content in the Variant Stream will fail to play without HDCP.
Clients without output copy protection SHOULD NOT load a Variant
Stream with an HDCP-LEVEL attribute unless its value is NONE.
VIDEO-RANGE
The value is an enumerated-string; valid strings are SDR and PQ.
The value MUST be SDR if all the video in the Variant Stream is
encoded using a reference opto-electronic transfer characteristic
function specified by the TransferCharacteristics code point 1
[CICP].
The value MUST be PQ if video in the Variant Stream includes some
content that is encoded using a reference opto-electronic transfer
characteristic function specified by the TransferCharacteristics
code point 16 or 18, and potentially other content qualifying as
SDR (see above). Note that certain TransferCharacteristics code
points use the same transfer function.
Otherwise the attribute MUST NOT be present.
AUDIO
The value is a quoted-string. It MUST match the value of the
GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Master
Playlist whose TYPE attribute is AUDIO. It indicates the set of
audio Renditions that SHOULD be used when playing the
presentation. See Section 4.4.4.2.1.
The AUDIO attribute is OPTIONAL.
VIDEO
The value is a quoted-string. It MUST match the value of the
GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Master
Playlist whose TYPE attribute is VIDEO. It indicates the set of
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video Renditions that SHOULD be used when playing the
presentation. See Section 4.4.4.2.1.
The VIDEO attribute is OPTIONAL.
SUBTITLES
The value is a quoted-string. It MUST match the value of the
GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Master
Playlist whose TYPE attribute is SUBTITLES. It indicates the set
of subtitle Renditions that can be used when playing the
presentation. See Section 4.4.4.2.1.
The SUBTITLES attribute is OPTIONAL.
CLOSED-CAPTIONS
The value can be either a quoted-string or an enumerated-string
with the value NONE. If the value is a quoted-string, it MUST
match the value of the GROUP-ID attribute of an EXT-X-MEDIA tag
elsewhere in the Playlist whose TYPE attribute is CLOSED-CAPTIONS,
and it indicates the set of closed-caption Renditions that can be
used when playing the presentation. See Section 4.4.4.2.1.
If the value is the enumerated-string value NONE, all EXT-X-
STREAM-INF tags MUST have this attribute with a value of NONE,
indicating that there are no closed captions in any Variant Stream
in the Master Playlist. Having closed captions in one Variant
Stream but not another can trigger playback inconsistencies.
The CLOSED-CAPTIONS attribute is OPTIONAL.
4.4.4.2.1. Alternative Renditions
When an EXT-X-STREAM-INF tag contains an AUDIO, VIDEO, SUBTITLES, or
CLOSED-CAPTIONS attribute, it indicates that alternative Renditions
of the content are available for playback of that Variant Stream.
When defining alternative Renditions, the following constraints MUST
be met to prevent client playback errors:
o All playable combinations of Renditions associated with an EXT-X-
STREAM-INF tag MUST have an aggregate bandwidth less than or equal
to the BANDWIDTH attribute of the EXT-X-STREAM-INF tag.
o If an EXT-X-STREAM-INF tag contains a RESOLUTION attribute and a
VIDEO attribute, then every alternative video Rendition MUST have
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an optimal display resolution matching the value of the RESOLUTION
attribute.
o Every alternative Rendition associated with an EXT-X-STREAM-INF
tag MUST meet the constraints for a Variant Stream described in
Section 6.2.4.
The URI attribute of the EXT-X-MEDIA tag is REQUIRED if the media
type is SUBTITLES, but OPTIONAL if the media type is VIDEO or AUDIO.
If the media type is VIDEO or AUDIO, a missing URI attribute
indicates that the media data for this Rendition is included in the
Media Playlist of any EXT-X-STREAM-INF tag referencing this EXT-
X-MEDIA tag. If the media TYPE is AUDIO and the URI attribute is
missing, clients MUST assume that the audio data for this Rendition
is present in every video Rendition specified by the EXT-X-STREAM-INF
tag.
The URI attribute of the EXT-X-MEDIA tag MUST NOT be included if the
media type is CLOSED-CAPTIONS.
4.4.4.3. EXT-X-I-FRAME-STREAM-INF
The EXT-X-I-FRAME-STREAM-INF tag identifies a Media Playlist file
containing the I-frames of a multimedia presentation. It stands
alone, in that it does not apply to a particular URI in the Master
Playlist. Its format is:
#EXT-X-I-FRAME-STREAM-INF:<attribute-list>
All attributes defined for the EXT-X-STREAM-INF tag (Section 4.4.4.2)
are also defined for the EXT-X-I-FRAME-STREAM-INF tag, except for the
FRAME-RATE, AUDIO, SUBTITLES, and CLOSED-CAPTIONS attributes. In
addition, the following attribute is defined:
URI
The value is a quoted-string containing a URI that identifies the
I-frame Media Playlist file. That Playlist file MUST contain an
EXT-X-I-FRAMES-ONLY tag.
Every EXT-X-I-FRAME-STREAM-INF tag MUST include a BANDWIDTH attribute
and a URI attribute.
The provisions in Section 4.4.4.2.1 also apply to EXT-X-I-FRAME-
STREAM-INF tags with a VIDEO attribute.
A Master Playlist that specifies alternative VIDEO Renditions and
I-frame Playlists SHOULD include an alternative I-frame VIDEO
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Rendition for each regular VIDEO Rendition, with the same NAME and
LANGUAGE attributes.
4.4.4.4. EXT-X-SESSION-DATA
The EXT-X-SESSION-DATA tag allows arbitrary session data to be
carried in a Master Playlist.
Its format is:
#EXT-X-SESSION-DATA:<attribute-list>
The following attributes are defined:
DATA-ID
The value of DATA-ID is a quoted-string that identifies a
particular data value. The DATA-ID SHOULD conform to a reverse
DNS naming convention, such as "com.example.movie.title"; however,
there is no central registration authority, so Playlist authors
SHOULD take care to choose a value that is unlikely to collide
with others. This attribute is REQUIRED.
VALUE
VALUE is a quoted-string. It contains the data identified by
DATA-ID. If the LANGUAGE is specified, VALUE SHOULD contain a
human-readable string written in the specified language.
URI
The value is a quoted-string containing a URI. The resource
identified by the URI MUST be formatted as JSON [RFC7159];
otherwise, clients may fail to interpret the resource.
LANGUAGE
The value is a quoted-string containing a language tag [RFC5646]
that identifies the language of the VALUE. This attribute is
OPTIONAL.
Each EXT-X-SESSION-DATA tag MUST contain either a VALUE or URI
attribute, but not both.
A Playlist MAY contain multiple EXT-X-SESSION-DATA tags with the same
DATA-ID attribute. A Playlist MUST NOT contain more than one EXT-X-
SESSION-DATA tag with the same DATA-ID attribute and the same
LANGUAGE attribute.
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4.4.4.5. EXT-X-SESSION-KEY
The EXT-X-SESSION-KEY tag allows encryption keys from Media Playlists
to be specified in a Master Playlist. This allows the client to
preload these keys without having to read the Media Playlist(s)
first.
Its format is:
#EXT-X-SESSION-KEY:<attribute-list>
All attributes defined for the EXT-X-KEY tag (Section 4.4.2.4) are
also defined for the EXT-X-SESSION-KEY, except that the value of the
METHOD attribute MUST NOT be NONE. If an EXT-X-SESSION-KEY is used,
the values of the METHOD, KEYFORMAT, and KEYFORMATVERSIONS attributes
MUST match any EXT-X-KEY with the same URI value.
EXT-X-SESSION-KEY tags SHOULD be added if multiple Variant Streams or
Renditions use the same encryption keys and formats. An EXT-X-
SESSION-KEY tag is not associated with any particular Media Playlist.
A Master Playlist MUST NOT contain more than one EXT-X-SESSION-KEY
tag with the same METHOD, URI, IV, KEYFORMAT, and KEYFORMATVERSIONS
attribute values.
The EXT-X-SESSION-KEY tag is optional.
4.4.5. Media or Master Playlist Tags
The tags in this section can appear in either Master Playlists or
Media Playlists. If one of these tags appears in a Master Playlist,
it SHOULD NOT appear in any Media Playlist referenced by that Master
Playlist. A tag that appears in both MUST have the same value;
otherwise, clients SHOULD ignore the value in the Media Playlist(s).
These tags MUST NOT appear more than once in a Playlist. If a tag
appears more than once, clients MUST fail to parse the Playlist.
4.4.5.1. EXT-X-INDEPENDENT-SEGMENTS
The EXT-X-INDEPENDENT-SEGMENTS tag indicates that all media samples
in a Media Segment can be decoded without information from other
segments. It applies to every Media Segment in the Playlist.
Its format is:
#EXT-X-INDEPENDENT-SEGMENTS
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If the EXT-X-INDEPENDENT-SEGMENTS tag appears in a Master Playlist,
it applies to every Media Segment in every Media Playlist in the
Master Playlist.
4.4.5.2. EXT-X-START
The EXT-X-START tag indicates a preferred point at which to start
playing a Playlist. By default, clients SHOULD start playback at
this point when beginning a playback session. This tag is OPTIONAL.
Its format is:
#EXT-X-START:<attribute-list>
The following attributes are defined:
TIME-OFFSET
The value of TIME-OFFSET is a signed-decimal-floating-point number
of seconds. A positive number indicates a time offset from the
beginning of the Playlist. A negative number indicates a negative
time offset from the end of the last Media Segment in the
Playlist. This attribute is REQUIRED.
The absolute value of TIME-OFFSET SHOULD NOT be larger than the
Playlist duration. If the absolute value of TIME-OFFSET exceeds
the duration of the Playlist, it indicates either the end of the
Playlist (if positive) or the beginning of the Playlist (if
negative).
If the Playlist does not contain the EXT-X-ENDLIST tag, the TIME-
OFFSET SHOULD NOT be within three target durations of the end of
the Playlist file.
PRECISE
The value is an enumerated-string; valid strings are YES and NO.
If the value is YES, clients SHOULD start playback at the Media
Segment containing the TIME-OFFSET, but SHOULD NOT render media
samples in that segment whose presentation times are prior to the
TIME-OFFSET. If the value is NO, clients SHOULD attempt to render
every media sample in that segment. This attribute is OPTIONAL.
If it is missing, its value should be treated as NO.
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4.4.5.3. EXT-X-DEFINE
The EXT-X-DEFINE tag provides a Playlist variable definition or
declaration. This tag is OPTIONAL.
Its format is:
#EXT-X-DEFINE:<attribute-list>
The following attributes are defined:
NAME
The value is a quoted-string which specifies the Variable Name.
All characters in the quoted-string MUST be from the following
set: [a..z], [A..Z], [0..9], '-', and '_'.
VALUE
The value is a quoted-string which specifies the Variable Value.
This attribute is REQUIRED if the EXT-X-DEFINE tag has a NAME
attribute.
IMPORT
The value is a quoted-string which specifies the Variable Name and
indicates that its value is that of the variable of the same name
in the Master Playlist. EXT-X-DEFINE tags containing the IMPORT
attribute MUST NOT occur in Master Playlists; they are only
allowed in Media Playlists.
If the IMPORT attribute value does not match any Variable Name
declared in the Master Playlist, or if the Media Playlist was not
loaded from a Master Playlist, the parser MUST fail to parse the
Playlist.
An EXT-X-DEFINE tag MUST contain either a NAME or an IMPORT
attribute, but not both.
An EXT-X-DEFINE tag MUST NOT specify the same Variable Name as any
other EXT-X-DEFINE tag in the same Playlist. Parsers that encounter
duplicate Variable Name declarations MUST fail to parse the Playlist.
EXT-X-DEFINE tags do NOT implicitly persist across Playlist reloads.
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5. Key Files
5.1. Structure of Key Files
An EXT-X-KEY tag with a URI attribute identifies a Key file. A Key
file contains a cipher key that can decrypt Media Segments in the
Playlist.
[AES_128] encryption uses 16-octet keys. If the KEYFORMAT of an EXT-
X-KEY tag is "identity", the Key file is a single packed array of 16
octets in binary format.
5.2. IV for AES-128
[AES_128] REQUIRES the same 16-octet IV to be supplied when
encrypting and decrypting. Varying this IV increases the strength of
the cipher.
An IV attribute on an EXT-X-KEY tag with a KEYFORMAT of "identity"
specifies an IV that can be used when decrypting Media Segments
encrypted with that Key file. IV values for AES-128 are 128-bit
numbers.
An EXT-X-KEY tag with a KEYFORMAT of "identity" that does not have an
IV attribute indicates that the Media Sequence Number is to be used
as the IV when decrypting a Media Segment, by putting its big-endian
binary representation into a 16-octet (128-bit) buffer and padding
(on the left) with zeros.
6. Client/Server Responsibilities
6.1. Introduction
This section describes how the server generates the Playlist and
Media Segments and how the client should download them for playback.
6.2. Server Responsibilities
6.2.1. General Server Responsibilities
The production of the source media is outside the scope of this
document, which simply presumes a source of continuous encoded media
containing the presentation.
The server MUST divide the source media into individual Media
Segments whose duration is less than or equal to a constant target
duration. Segments that are longer than the planned target duration
can trigger playback stalls and other errors.
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The server SHOULD attempt to divide the source media at points that
support effective decode of individual Media Segments, e.g., on
packet and key frame boundaries.
The server MUST create a URI for every Media Segment that enables its
clients to obtain the segment data. If a server supports partial
loading of resources (e.g., via HTTP Range requests), it MAY specify
segments as sub-ranges of larger resources using the EXT-X-BYTERANGE
tag.
The absence of media data (due to, for example, the temporary
unavailability of an encoder) SHOULD be signaled by adding one or
more Media Segments to the Playlist whose Segment durations add up to
the duration of absent media; these Media Segments MUST have EXT-
X-GAP tags applied to them. Attempting to download these segments
MAY produce an error, such as HTTP 404 or 410.
Any Media Segment that is specified in a Playlist loaded by a client
MUST be available for immediate download unless it has been marked
with an EXT-X-GAP tag; otherwise playback errors can occur. Once
download starts, its transfer rate SHOULD NOT be constrained by the
segment production process.
HTTP servers SHOULD transfer text files -- such as Playlists and
WebVTT segments -- using the "gzip" Content-Encoding if the client
indicates that it is prepared to accept it.
The server must create a Media Playlist file (Section 4) that
contains a URI for each Media Segment that the server wishes to make
available, in the order in which they are to be played.
The value of the EXT-X-VERSION tag (Section 4.4.1.2) SHOULD NOT be
greater than what is required for the tags and attributes in the
Playlist (see Section 7).
Changes to the Playlist file MUST be made atomically from the point
of view of the clients, or playback errors MAY occur.
The server MUST NOT change the Media Playlist file, except to:
Append lines to it (Section 6.2.1).
Remove Media Segment URIs from the Playlist in the order that they
appear, along with any tags that apply only to those segments
(Section 6.2.2).
Increment the value of the EXT-X-MEDIA-SEQUENCE or EXT-X-
DISCONTINUITY-SEQUENCE tags (Section 6.2.2).
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Add an EXT-X-ENDLIST tag to the Playlist (Section 6.2.1).
A Media Playlist has further constraints on its updates if it
contains an EXT-X-PLAYLIST-TYPE tag. An EXT-X-PLAYLIST-TYPE tag with
a value of VOD indicates that the Playlist file MUST NOT change. An
EXT-X-PLAYLIST-TYPE tag with a value of EVENT indicates that the
server MUST NOT change or delete any part of the Playlist file; it
MAY append lines to it.
The value of the EXT-X-TARGETDURATION tag in the Media Playlist MUST
NOT change. A typical target duration is 10 seconds.
Playlist changes other than those allowed here can trigger playback
errors and inconsistent client behavior.
Each Media Segment in a Media Playlist has an integer Discontinuity
Sequence Number. The Discontinuity Sequence Number can be used in
addition to the timestamps within the media to synchronize Media
Segments across different Renditions.
A segment's Discontinuity Sequence Number is the value of the EXT-X-
DISCONTINUITY-SEQUENCE tag (or zero if none) plus the number of EXT-
X-DISCONTINUITY tags in the Playlist preceding the URI line of the
segment.
The server MAY associate an absolute date and time with a Media
Segment by applying an EXT-X-PROGRAM-DATE-TIME tag to it. This
defines an informative mapping of the (wall-clock) date and time
specified by the tag to the first media timestamp in the segment,
which may be used as a basis for seeking, for display, or for other
purposes. If a server provides this mapping, it SHOULD apply an EXT-
X-PROGRAM-DATE-TIME tag to every segment that has an EXT-
X-DISCONTINUITY tag applied to it.
The Server MUST NOT add any EXT-X-PROGRAM-DATE-TIME tag to a Playlist
that would cause the mapping between program date and Media Segment
to become ambiguous.
The server MUST NOT remove an EXT-X-DATERANGE tag from a Playlist if
any date in the range maps to a Media Segment in the Playlist.
The server MUST NOT reuse the ID attribute value of an EXT-
X-DATERANGE tag for any new Date Range in the same Playlist.
Once the Following Range of a Date Range with an END-ON-NEXT=YES
attribute is added to a Playlist, the Server MUST NOT subsequently
add a Date Range with the same CLASS attribute whose START-DATE is
between that of the END-ON-NEXT=YES range and its Following Range.
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For Date Ranges with a PLANNED-DURATION attribute, the Server SHOULD
signal the actual end of the range once it has been established. It
can do so by adding another EXT-X-DATERANGE tag with the same ID
attribute value and either a DURATION or an END-DATE attribute or, if
the Date Range has an END-ON-NEXT=YES attribute, by adding a
Following Range.
If the Media Playlist contains the final Media Segment of the
presentation, then the Playlist file MUST contain the EXT-X-ENDLIST
tag; this allows clients to minimize unproductive Playlist reloads.
If a Media Playlist does not contain the EXT-X-ENDLIST tag, the
server MUST make a new version of the Playlist file available that
contains at least one new Media Segment. It MUST be made available
no later than 1.5 times the target duration after the previous time
the Playlist was updated with a Media Segment. This allows clients
to utilize the network efficiently.
If the server wishes to remove an entire presentation, it SHOULD
provide a clear indication to clients that the Playlist file is no
longer available (e.g., with an HTTP 404 or 410 response). It MUST
ensure that all Media Segments in the Playlist file remain available
to clients for at least the duration of the Playlist file at the time
of removal to prevent interruption of in-progress playback.
6.2.2. Live Playlists
The server MAY limit the availability of Media Segments by removing
Media Segments from the Playlist file (Section 6.2.1). If Media
Segments are to be removed, the Playlist file MUST contain an EXT-X-
MEDIA-SEQUENCE tag. Its value MUST be incremented by 1 for every
Media Segment that is removed from the Playlist file; it MUST NOT
decrease or wrap. Clients can malfunction if each Media Segment does
not have a consistent, unique Media Sequence Number.
Media Segments MUST be removed from the Playlist file in the order
that they appear in the Playlist; otherwise, client playback can
malfunction.
The server MUST NOT remove a Media Segment from a Playlist file
without an EXT-X-ENDLIST tag if that would produce a Playlist whose
duration is less than three times the target duration. Doing so can
trigger playback stalls.
The Availability Duration of a Media Segment is the duration of the
segment plus the duration of the longest-duration Playlist
distributed by the server containing that segment. If the server
removes a Media Segment URI from a Playlist that contains an EXT-
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X-ENDLIST tag, clients MUST be able to download the corresponding
Media Segment until the time of removal plus the segment's
Availability Duration. If the server removes a Media Segment URI
from a Playlist that does not contain an EXT-X-ENDLIST tag, clients
MUST be able to download the segment until the time at which it first
appeared in the Playlist plus the segment's Availability Duration.
If the server wishes to remove segments from a Media Playlist
containing an EXT-X-DISCONTINUITY tag, the Media Playlist MUST
contain an EXT-X-DISCONTINUITY-SEQUENCE tag. Without the EXT-X-
DISCONTINUITY-SEQUENCE tag, it can be impossible for a client to
locate corresponding segments between Renditions.
If the server removes an EXT-X-DISCONTINUITY tag from the Media
Playlist, it MUST increment the value of the EXT-X-DISCONTINUITY-
SEQUENCE tag so that the Discontinuity Sequence Numbers of the
segments still in the Media Playlist remain unchanged. The value of
the EXT-X-DISCONTINUITY-SEQUENCE tag MUST NOT decrease or wrap.
Clients can malfunction if each Media Segment does not have a
consistent Discontinuity Sequence Number.
If a server plans to remove a Media Segment after it is delivered to
clients over HTTP, it SHOULD ensure that the HTTP response contains
an Expires header that reflects the planned time-to-live.
A Live Playlist MUST NOT contain the EXT-X-PLAYLIST-TYPE tag, as no
value of that tag allows Media Segments to be removed.
6.2.3. Encrypting Media Segments
Media Segments MAY be encrypted. Every encrypted Media Segment MUST
have an EXT-X-KEY tag (Section 4.4.2.4) applied to it with a URI that
the client can use to obtain a Key file (Section 5) containing the
decryption key.
A Media Segment can only be encrypted with one encryption METHOD,
using one encryption key and IV. However, a server MAY offer
multiple ways to retrieve that key by providing multiple EXT-X-KEY
tags, each with a different KEYFORMAT attribute value.
The server MAY set the HTTP Expires header in the key response to
indicate the duration for which the key can be cached.
Any unencrypted Media Segment in a Playlist that is preceded by an
encrypted Media Segment MUST have an EXT-X-KEY tag applied to it with
a METHOD attribute of NONE. Otherwise, the client will misinterpret
those segments as encrypted.
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If the encryption METHOD is AES-128 and the Playlist does not contain
the EXT-X-I-FRAMES-ONLY tag, AES encryption as described in
Section 4.4.2.4 SHALL be applied to individual Media Segments.
If the encryption METHOD is AES-128 and the Playlist contains an EXT-
X-I-FRAMES-ONLY tag, the entire resource MUST be encrypted using
AES-128 CBC with PKCS7 padding [RFC5652]. Encryption MAY be
restarted on 16-byte block boundaries, unless the first block
contains an I-frame. The IV used for encryption MUST be either the
Media Sequence Number of the Media Segment or the value of the IV
attribute of the EXT-X-KEY tag, as described in Section 5.2. These
constraints allow a client to load and decrypt individual I-frames
specified as sub-ranges of regular encrypted Media Segments, and
their Media Initialization Sections.
If the encryption METHOD indicates Sample Encryption, media samples
MAY be encrypted prior to encapsulation in a Media Segment.
The server MUST NOT remove an EXT-X-KEY tag from the Playlist file if
it applies to any Media Segment in the Playlist file, or clients who
subsequently load that Playlist will be unable to decrypt those Media
Segments.
6.2.4. Providing Variant Streams
A server MAY offer multiple Media Playlist files to provide different
encodings of the same presentation. If it does so, it SHOULD provide
a Master Playlist file that lists each Variant Stream to allow
clients to switch between encodings dynamically.
Master Playlists describe regular Variant Streams with EXT-X-STREAM-
INF tags and I-frame Variant Streams with EXT-X-I-FRAME-STREAM-INF
tags.
If an EXT-X-STREAM-INF tag or EXT-X-I-FRAME-STREAM-INF tag contains
the CODECS attribute, the attribute value MUST include every media
format [RFC6381] present in any Media Segment in any of the
Renditions specified by the Variant Stream.
The server MUST meet the following constraints when producing Variant
Streams in order to allow clients to switch between them seamlessly:
Each Variant Stream MUST present the same content.
Matching content in Variant Streams MUST have matching timestamps.
This allows clients to synchronize the media.
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Matching content in Variant Streams MUST have matching
Discontinuity Sequence Numbers (see Section 4.4.3.3).
Each Media Playlist in each Variant Stream MUST have the same
target duration. The only exceptions are SUBTITLES Renditions and
Media Playlists containing an EXT-X-I-FRAMES-ONLY tag, which MAY
have different target durations if they have an EXT-X-PLAYLIST-
TYPE of VOD.
Content that appears in a Media Playlist of one Variant Stream but
not in another MUST appear either at the beginning or at the end
of the Media Playlist file and MUST NOT be longer than the target
duration.
If any Media Playlists have an EXT-X-PLAYLIST-TYPE tag, all Media
Playlists MUST have an EXT-X-PLAYLIST-TYPE tag with the same
value.
If the Playlist contains an EXT-X-PLAYLIST-TYPE tag with the value
of VOD, the first segment of every Media Playlist in every Variant
Stream MUST start at the same media timestamp.
If any Media Playlist in a Master Playlist contains an EXT-X-
PROGRAM-DATE-TIME tag, then all Media Playlists in that Master
Playlist MUST contain EXT-X-PROGRAM-DATE-TIME tags with consistent
mappings of date and time to media timestamps.
Each Variant Stream MUST contain the same set of Date Ranges. The
EXT-X-DATERANGE tags of corresponding Date Ranges MUST have the
same ID attribute value and contain the same set of attribute/
value pairs.
In addition, for broadest compatibility, Variant Streams SHOULD
contain the same encoded audio bitstream. This allows clients to
switch between Variant Streams without audible glitching.
The rules for Variant Streams also apply to alternative Renditions
(see Section 4.4.4.2.1).
6.3. Client Responsibilities
6.3.1. General Client Responsibilities
How the client obtains the URI to the Playlist file is outside the
scope of this document; it is presumed to have done so.
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The client obtains the Playlist file from the URI. If the Playlist
file so obtained is a Master Playlist, the client can select a
Variant Stream to load from the Master Playlist.
Clients MUST ensure that loaded Playlists comply with Section 4 and
that the EXT-X-VERSION tag, if present, specifies a protocol version
supported by the client; if either check fails, the client MUST NOT
attempt to use the Playlist, or unintended behavior could occur.
When parsing Playlist elements that are subject to variable
substitution, a Variable Reference whose Variable Name has been
provided by an EXT-X-DEFINE tag that precedes the Variable Reference
MUST be replaced by the corresponding Variable Value. Such
replacements themselves are NOT subject to variable substitution.
When parsing Playlist elements that are subject to variable
substitution, a Variable Reference whose Variable Name has NOT been
provided by an EXT-X-DEFINE tag preceding the Variable Reference MUST
trigger a parsing error.
If any URI element in a Playlist contains an URI scheme that the
client cannot handle, the client MUST stop playback. All clients
MUST support HTTP schemes.
To support forward compatibility, when parsing Playlists, clients
MUST:
o ignore any unrecognized tags.
o ignore any attribute/value pair with an unrecognized
AttributeName.
o ignore any tag containing an attribute/value pair of type
enumerated-string whose AttributeName is recognized but whose
AttributeValue is not recognized, unless the definition of the
attribute says otherwise.
Algorithms used by the client to switch between Variant Streams are
beyond the scope of this document.
6.3.2. Loading the Media Playlist File
Every time a Media Playlist is loaded or reloaded from a Playlist
URI, the client MUST determine the next Media Segment to load, as
described in Section 6.3.5, if it intends to play the presentation
normally (i.e., in Playlist order at the nominal playback rate).
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If the Media Playlist contains the EXT-X-MEDIA-SEQUENCE tag, the
client SHOULD assume that each Media Segment in it will become
unavailable at the time that the Playlist file was loaded plus the
duration of the Playlist file.
A client MAY use the segment Media Sequence Number to track the
location of a Media Segment within a Playlist when the Playlist is
reloaded.
A client MUST NOT assume that segments with the same Media Sequence
Number in different Variant Streams or Renditions have the same
position in the presentation; Playlists MAY have independent Media
Sequence Numbers. Instead, a client MUST use the relative position
of each segment on the Playlist timeline and its Discontinuity
Sequence Number to locate corresponding segments.
A client MUST load the Media Playlist file of every Rendition
selected for playback in order to locate the media specific to that
Rendition. But, to prevent unnecessary load on the server, it SHOULD
NOT load the Playlist file of any other Rendition.
For some Variant Streams, it is possible to select Renditions that do
not include the Rendition specified by the EXT-X-STREAM-INF tag. As
noted above, the client SHOULD NOT load that Rendition in those
cases.
6.3.3. Playing the Media Playlist File
The client SHALL choose which Media Segment to play first from the
Media Playlist when playback starts. If the EXT-X-ENDLIST tag is not
present and the client intends to play the media normally, the client
SHOULD NOT choose a segment that starts less than the duration of the
last segment in the Playlist plus two target durations from the end
of the Playlist file. Doing so can trigger playback stalls.
Normal playback can be achieved by playing the Media Segments in the
order that they appear in the Playlist. The client MAY present the
available media in any way it wishes, including normal playback,
random access, and trick modes.
The client SHOULD NOT attempt to load Media Segments that have been
marked with an EXT-X-GAP tag. Instead, clients are encouraged to
look for another Variant Stream of the same Rendition which does not
have the same gap, and play that instead.
The encoding parameters for samples in a Media Segment and across
multiple Media Segments in a Media Playlist SHOULD remain consistent.
However, clients SHOULD deal with encoding changes as they are
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encountered, for example, by scaling video content to accommodate a
resolution change. If the Variant Stream includes a RESOLUTION
attribute, clients SHOULD display all video within a rectangle with
the same proportions as that resolution.
Clients SHOULD be prepared to handle multiple tracks of a particular
type (e.g., audio or video). A client with no other preference
SHOULD choose the track with the lowest numerical track identifier
that it can play.
Clients SHOULD ignore private streams inside Transport Streams that
they do not recognize. Private streams can be used to support
different devices with the same stream, although stream authors
SHOULD be sensitive to the additional network load that this imposes.
The client MUST be prepared to reset its parser(s) and decoder(s)
before playing a Media Segment that has an EXT-X-DISCONTINUITY tag
applied to it; otherwise, playback errors can occur.
The client SHOULD attempt to load Media Segments in advance of when
they will be required for uninterrupted playback to compensate for
temporary variations in latency and throughput.
The client MAY use the value of the EXT-X-PROGRAM-DATE-TIME tag to
display the program origination time to the user. If the value
includes time zone information, the client SHALL take it into
account; if it does not, the client MAY assume the time to be local.
Note that dates in Playlists can refer to when the content was
produced (or to other times), which have no relation to the time of
playback.
If the first EXT-X-PROGRAM-DATE-TIME tag in a Playlist appears after
one or more Media Segment URIs, the client SHOULD extrapolate
backward from that tag (using EXTINF durations and/or media
timestamps) to associate dates with those segments. To associate a
date with any other Media Segment that does not have an EXT-X-
PROGRAM-DATE-TIME tag applied to it directly, the client SHOULD
extrapolate forward from the last EXT-X-PROGRAM-DATE-TIME tag
appearing before that segment in the Playlist.
6.3.4. Reloading the Media Playlist File
The client MUST periodically reload a Media Playlist file to learn
what media is currently available, unless it contains an EXT-X-
PLAYLIST-TYPE tag with a value of VOD, or a value of EVENT and the
EXT-X-ENDLIST tag is also present.
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However, the client MUST NOT attempt to reload the Playlist file more
frequently than specified by this section, in order to limit the
collective load on the server.
When a client loads a Playlist file for the first time or reloads a
Playlist file and finds that it has changed since the last time it
was loaded, the client MUST wait for at least the duration of the
last segment in the Playlist before attempting to reload the Playlist
file again, measured from the last time the client began loading the
Playlist file.
If the client reloads a Playlist file and finds that it has not
changed, then it MUST wait for a period of one-half the target
duration before retrying.
After reloading a Media Playlist, the client SHOULD verify that each
Media Segment in it has the same URI (and byte range, if specified)
as the Media Segment with the same Media Sequence Number in the
previous Media Playlist. It SHOULD halt playback if it does not, as
this normally indicates a server error.
In order to reduce server load, the client SHOULD NOT reload the
Playlist files of Variant Streams or alternate Renditions that are
not currently being played. If it decides to switch playback to a
different Variant Stream, it SHOULD stop reloading the Playlist of
the old Variant Stream and begin loading the Playlist of the new
Variant Stream. It can use the EXTINF durations and the constraints
in Section 6.2.4 to determine the approximate location of
corresponding media. Once media from the new Variant Stream has been
loaded, the timestamps in the Media Segments can be used to
synchronize the old and new timelines precisely.
A client MUST NOT attempt to use the Media Sequence Number to
synchronize between streams (see Section 6.3.2).
6.3.5. Determining the Next Segment to Load
The client MUST examine the Media Playlist file every time it is
loaded or reloaded to determine the next Media Segment to load, as
the set of available media MAY have changed.
The first segment to load is generally the segment that the client
has chosen to play first (see Section 6.3.3).
In order to play the presentation normally, the next Media Segment to
load is the one with the lowest Media Sequence Number that is greater
than the Media Sequence Number of the last Media Segment loaded.
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6.3.6. Decrypting Encrypted Media Segments
If a Media Playlist file contains an EXT-X-KEY tag that specifies a
Key file URI, the client can obtain that Key file and use the key
inside it to decrypt all Media Segments to which that EXT-X-KEY tag
applies.
A client MUST ignore any EXT-X-KEY tag with an unsupported or
unrecognized KEYFORMAT attribute, to allow for cross-device
addressability. If the Playlist contains a Media Segment to which
only EXT-X-KEY tags with unrecognized or unsupported KEYFORMAT
attributes are applied, playback SHOULD fail.
A client MUST NOT attempt to decrypt any segments whose EXT-X-KEY tag
has a METHOD attribute that it does not recognize.
If the encryption METHOD is AES-128, AES-128 CBC decryption SHALL be
applied to individual Media Segments, whose encryption format is
described in Section 4.4.2.4.
If the encryption METHOD is AES-128 and the Media Segment is part of
an I-frame Playlist (Section 4.4.3.6) and it has an EXT-X-BYTERANGE
tag applied to it, special care needs to be taken in loading and
decrypting the segment, because the resource identified by the URI is
encrypted in 16-byte blocks from the start of the resource.
The decrypted I-frame can be recovered by first widening its byte
range, as specified by the EXT-X-BYTERANGE tag, so that it starts and
ends on 16-byte boundaries from the start of the resource.
Next, the byte range is widened further to include a 16-byte block at
the beginning of the range. This 16-byte block allows the correct IV
for the following block to be calculated.
The widened byte range can then be loaded and decrypted with AES-128
CBC using an arbitrary IV. The number of bytes added to the
beginning and the end of the original byte range are discarded from
the decrypted bytes; what remains is the decrypted I-frame.
If the encryption METHOD indicates Sample Encryption, decryption
SHALL be applied to encrypted media samples within the Media Segment.
An EXT-X-KEY tag with a METHOD of NONE indicates that the Media
Segments it applies to are not encrypted.
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7. Protocol Version Compatibility
Protocol compatibility is specified by the EXT-X-VERSION tag. A
Playlist that contains tags or attributes that are not compatible
with protocol version 1 MUST include an EXT-X-VERSION tag.
A client MUST NOT attempt playback if it does not support the
protocol version specified by the EXT-X-VERSION tag, or unintended
behavior could occur.
A Media Playlist MUST indicate an EXT-X-VERSION of 2 or higher if it
contains:
o The IV attribute of the EXT-X-KEY tag.
A Media Playlist MUST indicate an EXT-X-VERSION of 3 or higher if it
contains:
o Floating-point EXTINF duration values.
A Media Playlist MUST indicate an EXT-X-VERSION of 4 or higher if it
contains:
o The EXT-X-BYTERANGE tag.
o The EXT-X-I-FRAMES-ONLY tag.
A Media Playlist MUST indicate an EXT-X-VERSION of 5 or higher if it
contains:
o An EXT-X-KEY tag with a METHOD of SAMPLE-AES.
o The KEYFORMAT and KEYFORMATVERSIONS attributes of the EXT-X-KEY
tag.
o The EXT-X-MAP tag.
A Media Playlist MUST indicate an EXT-X-VERSION of 6 or higher if it
contains:
o The EXT-X-MAP tag in a Media Playlist that does not contain EXT-
X-I-FRAMES-ONLY.
A Master Playlist MUST indicate an EXT-X-VERSION of 7 or higher if it
contains:
o "SERVICE" values for the INSTREAM-ID attribute of the EXT-X-MEDIA
tag.
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A Playlist MUST indicate an EXT-X-VERSION of 8 or higher if it
contains:
o Variable substitution.
The EXT-X-MEDIA tag and the AUDIO, VIDEO, and SUBTITLES attributes of
the EXT-X-STREAM-INF tag are backward compatible to protocol version
1, but playback on older clients may not be desirable. A server MAY
consider indicating an EXT-X-VERSION of 4 or higher in the Master
Playlist but is not required to do so.
The PROGRAM-ID attribute of the EXT-X-STREAM-INF and the EXT-X-I-
FRAME-STREAM-INF tags was removed in protocol version 6.
The EXT-X-ALLOW-CACHE tag was removed in protocol version 7.
8. Playlist Examples
8.1. Simple Media Playlist
#EXTM3U
#EXT-X-TARGETDURATION:10
#EXT-X-VERSION:3
#EXTINF:9.009,
http://media.example.com/first.ts
#EXTINF:9.009,
http://media.example.com/second.ts
#EXTINF:3.003,
http://media.example.com/third.ts
#EXT-X-ENDLIST
8.2. Live Media Playlist Using HTTPS
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:8
#EXT-X-MEDIA-SEQUENCE:2680
#EXTINF:7.975,
https://priv.example.com/fileSequence2680.ts
#EXTINF:7.941,
https://priv.example.com/fileSequence2681.ts
#EXTINF:7.975,
https://priv.example.com/fileSequence2682.ts
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8.3. Playlist with Encrypted Media Segments
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-MEDIA-SEQUENCE:7794
#EXT-X-TARGETDURATION:15
#EXT-X-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=52"
#EXTINF:2.833,
http://media.example.com/fileSequence52-A.ts
#EXTINF:15.0,
http://media.example.com/fileSequence52-B.ts
#EXTINF:13.333,
http://media.example.com/fileSequence52-C.ts
#EXT-X-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=53"
#EXTINF:15.0,
http://media.example.com/fileSequence53-A.ts
8.4. Master Playlist
#EXTM3U
#EXT-X-STREAM-INF:BANDWIDTH=1280000,AVERAGE-BANDWIDTH=1000000
http://example.com/low.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=2560000,AVERAGE-BANDWIDTH=2000000
http://example.com/mid.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=7680000,AVERAGE-BANDWIDTH=6000000
http://example.com/hi.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5"
http://example.com/audio-only.m3u8
8.5. Master Playlist with I-Frames
#EXTM3U
#EXT-X-STREAM-INF:BANDWIDTH=1280000
low/audio-video.m3u8
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=86000,URI="low/iframe.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=2560000
mid/audio-video.m3u8
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=150000,URI="mid/iframe.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=7680000
hi/audio-video.m3u8
#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=550000,URI="hi/iframe.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5"
audio-only.m3u8
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8.6. Master Playlist with Alternative Audio
In this example, the CODECS attributes have been condensed for space.
A '\' is used to indicate that the tag continues on the following
line with whitespace removed:
#EXTM3U
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="English", \
DEFAULT=YES,AUTOSELECT=YES,LANGUAGE="en", \
URI="main/english-audio.m3u8"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="Deutsch", \
DEFAULT=NO,AUTOSELECT=YES,LANGUAGE="de", \
URI="main/german-audio.m3u8"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="Commentary", \
DEFAULT=NO,AUTOSELECT=NO,LANGUAGE="en", \
URI="commentary/audio-only.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="...",AUDIO="aac"
low/video-only.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=2560000,CODECS="...",AUDIO="aac"
mid/video-only.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=7680000,CODECS="...",AUDIO="aac"
hi/video-only.m3u8
#EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5",AUDIO="aac"
main/english-audio.m3u8
8.7. Master Playlist with Alternative Video
This example shows three different video Renditions (Main,
Centerfield, and Dugout) and three different Variant Streams (low,
mid, and high). In this example, clients that did not support the
EXT-X-MEDIA tag and the VIDEO attribute of the EXT-X-STREAM-INF tag
would only be able to play the video Rendition "Main".
Since the EXT-X-STREAM-INF tag has no AUDIO attribute, all video
Renditions would be required to contain the audio.
In this example, the CODECS attributes have been condensed for space.
A '\' is used to indicate that the tag continues on the following
line with whitespace removed:
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#EXTM3U
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="low",NAME="Main", \
DEFAULT=YES,URI="low/main/audio-video.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="low",NAME="Centerfield", \
DEFAULT=NO,URI="low/centerfield/audio-video.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="low",NAME="Dugout", \
DEFAULT=NO,URI="low/dugout/audio-video.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="...",VIDEO="low"
low/main/audio-video.m3u8
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="mid",NAME="Main", \
DEFAULT=YES,URI="mid/main/audio-video.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="mid",NAME="Centerfield", \
DEFAULT=NO,URI="mid/centerfield/audio-video.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="mid",NAME="Dugout", \
DEFAULT=NO,URI="mid/dugout/audio-video.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=2560000,CODECS="...",VIDEO="mid"
mid/main/audio-video.m3u8
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="hi",NAME="Main", \
DEFAULT=YES,URI="hi/main/audio-video.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="hi",NAME="Centerfield", \
DEFAULT=NO,URI="hi/centerfield/audio-video.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="hi",NAME="Dugout", \
DEFAULT=NO,URI="hi/dugout/audio-video.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=7680000,CODECS="...",VIDEO="hi"
hi/main/audio-video.m3u8
8.8. Session Data in a Master Playlist
In this example, only the EXT-X-SESSION-DATA is shown:
#EXT-X-SESSION-DATA:DATA-ID="com.example.lyrics",URI="lyrics.json"
#EXT-X-SESSION-DATA:DATA-ID="com.example.title",LANGUAGE="en", \
VALUE="This is an example"
#EXT-X-SESSION-DATA:DATA-ID="com.example.title",LANGUAGE="es", \
VALUE="Este es un ejemplo"
8.9. CHARACTERISTICS Attribute Containing Multiple Characteristics
Certain characteristics are valid in combination, as in:
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CHARACTERISTICS=
"public.accessibility.transcribes-spoken-dialog,public.easy-to-read"
8.10. EXT-X-DATERANGE Carrying SCTE-35 Tags
This example shows two EXT-X-DATERANGE tags that describe a single
Date Range, with an SCTE-35 "out" splice_insert() command that is
subsequently updated with an SCTE-35 "in" splice_insert() command.
#EXTM3U
...
#EXT-X-DATERANGE:ID="splice-6FFFFFF0",START-DATE="2014-03-05T11:
15:00Z",PLANNED-DURATION=59.993,SCTE35-OUT=0xFC002F0000000000FF0
00014056FFFFFF000E011622DCAFF000052636200000000000A0008029896F50
000008700000000
... Media Segment declarations for 60s worth of media
#EXT-X-DATERANGE:ID="splice-6FFFFFF0",DURATION=59.993,SCTE35-IN=
0xFC002A0000000000FF00000F056FFFFFF000401162802E6100000000000A00
08029896F50000008700000000
...
9. Contributors
Significant contributions to the design of this protocol were made by
Jim Batson, David Biderman, Bill May, Roger Pantos, Alan Tseng, and
Eryk Vershen. Stuart Cheshire helped edit the specification.
Significant contributions to the update of this protocol were made by
Bill May and Eryk Vershen.
10. IANA Considerations
IANA has registered the following media type [RFC2046]:
Type name: application
Subtype name: vnd.apple.mpegurl
Required parameters: none
Optional parameters: none
Encoding considerations: encoded as UTF-8, which is 8-bit text. This
media type may require encoding on transports not capable of handling
8-bit text. See Section 4 for more information.
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Security considerations: See Section 11.
Compression: this media type does not employ compression.
Interoperability considerations: There are no byte-ordering issues,
since files are 8-bit text. Applications could encounter
unrecognized tags, which SHOULD be ignored.
Published specification: see Section 4.
Applications that use this media type: Multimedia applications such
as the iPhone media player in iOS 3.0 and later and QuickTime Player
in Mac OS X version 10.6 and later.
Fragment identifier considerations: no Fragment Identifiers are
defined for this media type.
Additional information:
Deprecated alias names for this type: none
Magic number(s): #EXTM3U
File extension(s): .m3u8, .m3u (see Section 4)
Macintosh file type code(s): none
Person & email address to contact for further information: David
Singer, singer AT apple.com.
Intended usage: LIMITED USE
Restrictions on usage: none
Author: Roger Pantos
Change Controller: David Singer
11. Security Considerations
Since the protocol generally uses HTTP to transfer data, most of the
same security considerations apply. See Section 15 of HTTP
[RFC7230].
Media file parsers are typically subject to "fuzzing" attacks.
Implementors SHOULD pay particular attention to code that will parse
data received from a server and ensure that all possible inputs are
handled correctly.
Playlist files contain URIs, which clients will use to make network
requests of arbitrary entities. Clients SHOULD range-check responses
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to prevent buffer overflows. See also the Security Considerations
section of "Uniform Resource Identifier (URI): Generic Syntax"
[RFC3986].
Apart from URL resolution, this format does not employ any form of
active content.
Clients SHOULD limit each playback session to a reasonable number of
concurrent downloads (for example, four) to avoid contributing to
denial-of-service attacks.
HTTP requests often include session state ("cookies"), which may
contain private user data. Implementations MUST follow cookie
restriction and expiry rules specified by "HTTP State Management
Mechanism" [RFC6265] to protect themselves from attack. See also the
Security Considerations section of that document, and "Use of HTTP
State Management" [RFC2964].
Encryption keys are specified by URI. The delivery of these keys
SHOULD be secured by a mechanism such as HTTP Over TLS [RFC2818]
(formerly SSL) in conjunction with a secure realm or a session token.
12. References
12.1. Normative References
[AC_3] Advanced Television Systems Committee, "Digital Audio
Compression (AC-3) (E-AC-3)", ATSC Standard A/52:2010,
November 2010, <http://atsc.org/wp-
content/uploads/2015/03/A52-201212-17.pdf>.
[AES_128] National Institute of Standards and Technology, "Advanced
Encryption Standard (AES)", FIPS PUB 197, DOI
10.6028/NIST.FIPS.197, November 2001,
<http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf>.
[CEA608] Consumer Technology Association, "Line 21 Data Services",
ANSI/CTA Standard 608-E, April 2008,
<https://standards.cta.tech/kwspub/published_docs/
ANSI-CTA-608-E-R-2014-Preview.pdf>.
[CEA708] Consumer Technology Association, "Digital Television (DTV)
Closed Captioning", ANSI/CTA Standard CEA-708-E, August
2013, <https://standards.cta.tech/kwspub/published_docs/
ANSI-CTA-708-E-Preview.pdf>.
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[CICP] International Organization for Standardization,
"Information technology - MPEG systems technologies - Part
8: Coding-independent code points", ISO/IEC International
Standard 23001-8:2016, 2016, <https://www.iso.org/obp/
ui/#iso:std:iso-iec:23001:-8:ed-2:v1:en>.
[CMAF] International Organization for Standardization,
"Information technology -- Multimedia application format
(MPEG-A) -- Part 19: Common media application format
(CMAF) for segmented media", ISO/IEC International
Standard 23000-19:2017, December 2017,
<https://www.iso.org/standard/71975.html>.
[COMMON_ENC]
International Organization for Standardization,
"Information technology -- MPEG systems technologies --
Part 7: Common encryption in ISO base media file format
files", ISO/IEC International Standard 23001-7:2016,
February 2016, <http://www.iso.org/iso/
catalogue_detail.htm?csnumber=68042>.
[H_264] International Telecommunications Union, "Advanced video
coding for generic audiovisual services", January 2012,
<http://www.itu.int/rec/T-REC-H.264>.
[HDCP] Digital Content Protection LLC, "High-bandwidth Digital
Content Protection System - Mapping HDCP to HDMI",
February 2013, <http://www.digital-
cp.com/sites/default/files/specifications/
HDCP%20on%20HDMI%20Specification%20Rev2_2_Final1.pdf>.
[IMSC1] W3C, "TTML Profiles for Internet Media Subtitles and
Captions 1.0 (IMSC1)", April 2016,
<https://www.w3.org/TR/ttml-imsc1/>.
[ISO_13818]
International Organization for Standardization, "Generic
coding of moving pictures and associated audio
information", ISO/IEC International Standard 13818:2007,
October 2007,
<http://www.iso.org/iso/catalogue_detail?csnumber=44169>.
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[ISO_13818_3]
International Organization for Standardization, "Generic
coding of moving pictures and associated audio information
-- Part 3: Audio", ISO/IEC International
Standard 13818-3:1998, April 1998,
<http://www.iso.org/iso/home/store/catalogue_tc/
catalogue_detail.htm?csnumber=26797>.
[ISO_13818_7]
International Organization for Standardization, "Generic
coding of moving pictures and associated audio information
-- Part 7: Advanced Audio Coding (AAC)", ISO/IEC
International Standard 13818-7:2006, January 2006,
<http://www.iso.org/iso/home/store/catalogue_tc/
catalogue_detail.htm?csnumber=43345>.
[ISO_14496]
International Organization for Standardization,
"Information technology -- Coding of audio-visual objects
-- Part 3: Audio", ISO/IEC International
Standard 14496-3:2009, 2009,
<http://www.iso.org/iso/catalogue_detail?csnumber=53943>.
[ISO_8601]
International Organization for Standardization, "Data
elements and interchange formats -- Information
interchange -- Representation of dates and times", ISO/IEC
International Standard 8601:2004, December 2004,
<http://www.iso.org/iso/catalogue_detail?csnumber=40874>.
[ISOBMFF] International Organization for Standardization,
"Information technology -- Coding of audio-visual objects
-- Part 12: ISO base media file format", ISO/IEC
International Standard 14496-12:2015, December 2015,
<http://www.iso.org/iso/
catalogue_detail.htm?csnumber=68960>.
[MP4_TIMED_TEXT]
International Organization for Standardization,
"Information technology -- Coding of audio-visual objects
-- Part 30: Timed text and other visual overlays in ISO
base media file format", ISO/IEC International
Standard 14496-30:2014, March 2014,
<https://www.iso.org/standard/63107.html>.
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[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>.
[RFC2964] Moore, K. and N. Freed, "Use of HTTP State Management",
BCP 44, RFC 2964, DOI 10.17487/RFC2964, October 2000,
<https://www.rfc-editor.org/info/rfc2964>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
September 2009, <https://www.rfc-editor.org/info/rfc5646>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/info/rfc6265>.
[RFC6381] Gellens, R., Singer, D., and P. Frojdh, "The 'Codecs' and
'Profiles' Parameters for "Bucket" Media Types", RFC 6381,
DOI 10.17487/RFC6381, August 2011,
<https://www.rfc-editor.org/info/rfc6381>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.
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[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8216] Pantos, R., Ed. and W. May, "HTTP Live Streaming",
RFC 8216, DOI 10.17487/RFC8216, August 2017,
<https://www.rfc-editor.org/info/rfc8216>.
[SCTE35] Society of Cable Telecommunications Engineers, "Digital
Program Insertion Cueing Message for Cable", ANSI/SCTE 35,
August 2014, <http://www.scte.org/documents/pdf/Standards/
ANSI_SCTE%2035%202014.pdf>.
[US_ASCII]
American National Standards Institute, "Coded Character
Sets - 7-Bit American National Standard Code for
Information Interchange (7-Bit ASCII)", ANSI X3.4,
December 1986.
[WebVTT] World Wide Web Consortium (W3C), ""WebVTT: The Web Video
Text Tracks Format", Draft Community Group Report", July
2013, <http://dev.w3.org/html5/webvtt/>.
12.2. Informative References
[ID3] ID3.org, "The ID3 audio file data tagging format",
<http://www.id3.org/Developer_Information>.
[M3U] Nullsoft, Inc., "The M3U Playlist format, originally
invented for the Winamp media player",
<http://wikipedia.org/wiki/M3U>.
[SampleEnc]
Apple Inc., "MPEG-2 Stream Encryption Format for HTTP Live
Streaming", <https://developer.apple.com/library/ios/docum
entation/AudioVideo/Conceptual/HLS_Sample_Encryption/>.
[UNICODE] The Unicode Consortium, "The Unicode Standard",
<https://www.unicode.org/versions/latest/>.
[UTI] Apple Inc., "Uniform Type Identifier", <http://developer.a
pple.com/library/ios/#documentation/general/conceptual/
DevPedia-CocoaCore/UniformTypeIdentifier.html>.
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Appendix A. Changes from RFC 8216
Several changes have been made since the publication of RFC 8216
[RFC8216].
The following tags have been added: EXT-X-GAP and EXT-X-DEFINE
(including variable substitution).
IMSC has been added to the set of recognized subtitle formats.
The VIDEO-RANGE attribute has been added to the EXT-X-STREAM-INF and
EXT-X-I-FRAME-STREAM-INF tags.
TYPE-1 has been added as a defined value for the HDCP-LEVEL
attribute.
The minimum new segment publication latency has been removed from
server timing model.
The Availability Duration of a Media Segment now depends on the
presence of an EXT-X-ENDLIST tag.
The recommended playlist offset to join a live stream has changed.
The minimum delay before reloading a Playlist file has changed.
There have been a number of minor editorial changes.
Author's Address
Roger Pantos (editor)
Apple Inc.
Cupertino, California
United States
Email: http-live-streaming-review@group.apple.com
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