Merge branch 'AudioKit:main' into main

jcavar · Nov 17, 2024 · f6a1b7f · f6a1b7f
2 parents 7fd9b78 + c6e2489
commit f6a1b7f
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diff --git a/Sources/AudioKit/Audio Files/AVAudioPCMBuffer+Processing.swift b/Sources/AudioKit/Audio Files/AVAudioPCMBuffer+Processing.swift
@@ -253,3 +253,19 @@ extension AVAudioPCMBuffer {
         return value
     }
 }
+
+public extension AVAudioPCMBuffer {
+    func mixToMono() -> AVAudioPCMBuffer {
+        let newFormat = AVAudioFormat(standardFormatWithSampleRate: format.sampleRate, channels: 1)!
+        let buffer = AVAudioPCMBuffer(pcmFormat: newFormat, frameCapacity: frameLength)!
+        buffer.frameLength = frameLength
+
+        let stride = vDSP_Stride(1)
+        let result = buffer.floatChannelData![0]
+        for channel in 0 ..< format.channelCount {
+            let channelData = self.floatChannelData![Int(channel)]
+            vDSP_vadd(channelData, stride, result, stride, result, stride, vDSP_Length(frameLength))
+        }
+        return buffer
+    }
+}
diff --git a/Tests/AudioKitTests/Extension Tests/AVAudioPCMBufferMixToMonoTests.swift b/Tests/AudioKitTests/Extension Tests/AVAudioPCMBufferMixToMonoTests.swift
@@ -0,0 +1,44 @@
+import AudioKit
+import AVFoundation
+import Foundation
+import XCTest
+
+class AVAudioPCMBufferMixToMonoTests: XCTestCase {
+    let sampleRate: Double = 44100
+    lazy var capacity = 10 * UInt32(sampleRate)
+    lazy var format = AVAudioFormat(standardFormatWithSampleRate: sampleRate, channels: 2)!
+    lazy var buffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: capacity)!
+    lazy var data = buffer.floatChannelData!
+
+    func testMixToMonoCancellation() {
+        for index in 0..<capacity {
+            data[0][Int(index)] = -1
+            data[1][Int(index)] = 1
+        }
+        buffer.frameLength = capacity
+
+        let mono = buffer.mixToMono()
+
+        XCTAssertEqual(mono.format.channelCount, 1)
+        XCTAssertEqual(mono.frameCapacity, capacity)
+        XCTAssertEqual(mono.frameLength, capacity)
+
+        XCTAssertTrue(mono.toFloatChannelData()![0].allSatisfy { $0 == 0 })
+    }
+
+    func testMixToMonoDouble() {
+        for index in 0..<capacity {
+            data[0][Int(index)] = 1
+            data[1][Int(index)] = 1
+        }
+        buffer.frameLength = capacity
+
+        let mono = buffer.mixToMono()
+
+        XCTAssertEqual(mono.format.channelCount, 1)
+        XCTAssertEqual(mono.frameCapacity, capacity)
+        XCTAssertEqual(mono.frameLength, capacity)
+
+        XCTAssertTrue(mono.toFloatChannelData()![0].allSatisfy { $0 == 2 })
+    }
+}