How do I call CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer?

Question

I\'m trying to figure out how to call this AVFoundation function in Swift. I\'ve spent a ton of time fiddling with declarations and syntax, and got this far.

Answer 1

Disclaimer: I have just tried to translate the code from Reading audio samples via AVAssetReader to Swift, and verified that it compiles. I have not tested if it really works.

// Needs to be initialized somehow, even if we take only the address
var audioBufferList = AudioBufferList(mNumberBuffers: 1,
      mBuffers: AudioBuffer(mNumberChannels: 0, mDataByteSize: 0, mData: nil))

var buffer: Unmanaged? = nil

CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
    sampleBuffer,
    nil,
    &audioBufferList,
    UInt(sizeof(audioBufferList.dynamicType)),
    nil,
    nil,
    UInt32(kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment),
    &buffer
)

// Ensure that the buffer is released automatically.
let buf = buffer!.takeRetainedValue() 

// Create UnsafeBufferPointer from the variable length array starting at audioBufferList.mBuffers
let audioBuffers = UnsafeBufferPointer(start: &audioBufferList.mBuffers,
    count: Int(audioBufferList.mNumberBuffers))

for audioBuffer in audioBuffers {
    // Create UnsafeBufferPointer from the buffer data pointer
    var samples = UnsafeMutableBufferPointer(start: UnsafeMutablePointer(audioBuffer.mData),
        count: Int(audioBuffer.mDataByteSize)/sizeof(Int16))

    for sample in samples {
        // ....
    }
}