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ALAC : Unify interface between libsndfile and ALAC codec.
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@erikd
erikd committed Mar 9, 2012
1 parent 80f0c07 commit d93bfaa
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Showing 8 changed files with 304 additions and 783 deletions.
10 changes: 10 additions & 0 deletions ChangeLog
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Original file line number Diff line number Diff line change
@@ -1,3 +1,13 @@
2012-02-10 Erik de Castro Lopo <erikd AT mega-nerd DOT com>

* src/ALAC/ src/alac.c
Unify the interface between libsndfile and Apple ALAC codec. Regardless of
file bit width samples are now passed between the two as int32_t that are
justified towards the most significant bit. Without this modification, 16
conversion functions would have been needed between the libsndfile (short,
int, float, double) types and the ALAC types (16, 20, 24 and 32 bit). With
this mod, only 4 are needed.

2012-02-09 Erik de Castro Lopo <erikd AT mega-nerd DOT com>

* configure.ac src/sfconfig.h src/sfendian.h
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7 changes: 4 additions & 3 deletions src/ALAC/alac_codec.h
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
/*
* Copyright (c) 2011 Apple Inc. All rights reserved.
* Copyright (C) 2012 Erik de Castro Lopo <erikd@mega-nerd.com>
*
* @APPLE_APACHE_LICENSE_HEADER_START@
*
Expand Down Expand Up @@ -86,11 +87,11 @@ typedef struct alac_encoder_s
int32_t alac_decoder_init (ALAC_DECODER *p, void * inMagicCookie, uint32_t inMagicCookieSize) ;
int32_t alac_encoder_init (ALAC_ENCODER *p, uint32_t samplerate, uint32_t channels, uint32_t format_flags, uint32_t frameSize) ;

int32_t alac_decode (ALAC_DECODER *, struct BitBuffer * bits, uint8_t * sampleBuffer,
int32_t alac_decode (ALAC_DECODER *, struct BitBuffer * bits, int32_t * sampleBuffer,
uint32_t numSamples, uint32_t numChannels, uint32_t * outNumSamples) ;

int32_t alac_encode (ALAC_ENCODER *p, uint32_t numChannels, uint32_t bytesPerPacket,
unsigned char * theReadBuffer, unsigned char * theWriteBuffer,
int32_t alac_encode (ALAC_ENCODER *p, uint32_t numChannels, uint32_t numSamples,
int32_t * theReadBuffer, unsigned char * theWriteBuffer,
int32_t * ioNumBytes) ;

void alac_set_fastmode(ALAC_ENCODER * p, int32_t fast) ;
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91 changes: 19 additions & 72 deletions src/ALAC/alac_decoder.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
/*
* Copyright (c) 2011 Apple Inc. All rights reserved.
* Copyright (C) 2012 Erik de Castro Lopo <erikd@mega-nerd.com>
*
* @APPLE_APACHE_LICENSE_HEADER_START@
*
Expand Down Expand Up @@ -47,8 +48,6 @@ const uint32_t kMaxBitDepth = 32; // max allowed bit depth is 32
static int32_t alac_fill_element (struct BitBuffer * bits) ;
static int32_t alac_data_stream_element (struct BitBuffer * bits) ;

static void Zero16( int16_t * buffer, uint32_t numItems, uint32_t stride );
static void Zero24( uint8_t * buffer, uint32_t numItems, uint32_t stride );
static void Zero32( int32_t * buffer, uint32_t numItems, uint32_t stride );


Expand Down Expand Up @@ -131,7 +130,7 @@ alac_decoder_init (ALAC_DECODER *p, void * inMagicCookie, uint32_t inMagicCookie
the bitstream
*/
int32_t
alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, uint8_t * sampleBuffer, uint32_t numSamples, uint32_t numChannels, uint32_t * outNumSamples)
alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, int32_t * sampleBuffer, uint32_t numSamples, uint32_t numChannels, uint32_t * outNumSamples)
{
BitBuffer shiftBits;
uint32_t bits1, bits2;
Expand All @@ -153,9 +152,6 @@ alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, uint8_t * sampleBuffer, u
uint32_t denShiftU, denShiftV;
uint16_t pbFactorU, pbFactorV;
uint16_t pb;
int16_t * out16;
uint8_t * out20;
uint8_t * out24;
int32_t * out32;
uint8_t headerByte;
uint8_t partialFrame;
Expand Down Expand Up @@ -304,23 +300,23 @@ alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, uint8_t * sampleBuffer, u
switch ( p->mConfig.bitDepth )
{
case 16:
out16 = &((int16_t *)sampleBuffer)[channelIndex];
out32 = sampleBuffer + channelIndex;
for ( i = 0, j = 0; i < numSamples; i++, j += numChannels )
out16[j] = (int16_t) p->mMixBufferU[i];
out32[j] = p->mMixBufferU[i] << 16;
break;
case 20:
out20 = (uint8_t *)sampleBuffer + (channelIndex * 3);
copyPredictorTo20( p->mMixBufferU, out20, numChannels, numSamples );
out32 = sampleBuffer + channelIndex;
copyPredictorTo20( p->mMixBufferU, out32, numChannels, numSamples );
break;
case 24:
out24 = (uint8_t *)sampleBuffer + (channelIndex * 3);
out32 = sampleBuffer + channelIndex;
if ( bytesShifted != 0 )
copyPredictorTo24Shift( p->mMixBufferU, p->mShiftBuffer, out24, numChannels, numSamples, bytesShifted );
copyPredictorTo24Shift( p->mMixBufferU, p->mShiftBuffer, out32, numChannels, numSamples, bytesShifted );
else
copyPredictorTo24( p->mMixBufferU, out24, numChannels, numSamples );
copyPredictorTo24( p->mMixBufferU, out32, numChannels, numSamples );
break;
case 32:
out32 = &((int32_t *)sampleBuffer)[channelIndex];
out32 = sampleBuffer + channelIndex;
if ( bytesShifted != 0 )
copyPredictorTo32Shift( p->mMixBufferU, p->mShiftBuffer, out32, numChannels, numSamples, bytesShifted );
else
Expand Down Expand Up @@ -493,20 +489,20 @@ alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, uint8_t * sampleBuffer, u
switch ( p->mConfig.bitDepth )
{
case 16:
out16 = &((int16_t *)sampleBuffer)[channelIndex];
unmix16( p->mMixBufferU, p->mMixBufferV, out16, numChannels, numSamples, mixBits, mixRes );
out32 = sampleBuffer + channelIndex;
unmix16( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples, mixBits, mixRes );
break;
case 20:
out20 = (uint8_t *)sampleBuffer + (channelIndex * 3);
unmix20( p->mMixBufferU, p->mMixBufferV, out20, numChannels, numSamples, mixBits, mixRes );
out32 = sampleBuffer + channelIndex;
unmix20( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples, mixBits, mixRes );
break;
case 24:
out24 = (uint8_t *)sampleBuffer + (channelIndex * 3);
unmix24( p->mMixBufferU, p->mMixBufferV, out24, numChannels, numSamples,
out32 = sampleBuffer + channelIndex;
unmix24( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples,
mixBits, mixRes, p->mShiftBuffer, bytesShifted );
break;
case 32:
out32 = &((int32_t *)sampleBuffer)[channelIndex];
out32 = sampleBuffer + channelIndex;
unmix32( p->mMixBufferU, p->mMixBufferV, out32, numChannels, numSamples,
mixBits, mixRes, p->mShiftBuffer, bytesShifted );
break;
Expand Down Expand Up @@ -562,27 +558,8 @@ alac_decode (ALAC_DECODER *p, struct BitBuffer * bits, uint8_t * sampleBuffer, u
// if we get here and haven't decoded all of the requested channels, fill the remaining channels with zeros
for ( ; channelIndex < numChannels; channelIndex++ )
{
switch ( p->mConfig.bitDepth )
{
case 16:
{
int16_t * fill16 = &((int16_t *)sampleBuffer)[channelIndex];
Zero16( fill16, numSamples, numChannels );
break;
}
case 24:
{
uint8_t * fill24 = (uint8_t *)sampleBuffer + (channelIndex * 3);
Zero24( fill24, numSamples, numChannels );
break;
}
case 32:
{
int32_t * fill32 = &((int32_t *)sampleBuffer)[channelIndex];
Zero32( fill32, numSamples, numChannels );
break;
}
}
int32_t * fill32 = sampleBuffer + channelIndex;
Zero32( fill32, numSamples, numChannels );
}

Exit:
Expand Down Expand Up @@ -652,36 +629,6 @@ alac_data_stream_element (struct BitBuffer * bits)
ZeroN()
- helper routines to clear out output channel buffers when decoding fewer channels than requested
*/
static void Zero16( int16_t * buffer, uint32_t numItems, uint32_t stride )
{
if ( stride == 1 )
{
memset( buffer, 0, numItems * sizeof(int16_t) );
}
else
{
for ( uint32_t indx = 0; indx < (numItems * stride); indx += stride )
buffer[indx] = 0;
}
}

static void Zero24( uint8_t * buffer, uint32_t numItems, uint32_t stride )
{
if ( stride == 1 )
{
memset( buffer, 0, numItems * 3 );
}
else
{
for ( uint32_t indx = 0; indx < (numItems * stride * 3); indx += (stride * 3) )
{
buffer[indx + 0] = 0;
buffer[indx + 1] = 0;
buffer[indx + 2] = 0;
}
}
}

static void Zero32( int32_t * buffer, uint32_t numItems, uint32_t stride )
{
if ( stride == 1 )
Expand Down
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