format CMSampleBuffer from/to AudioBufferList/Data

audio_format.swift

func data(from sampleBuffer: CMSampleBuffer) -> Data {
    var abl = AudioBufferList()
    var blockBuffer: CMBlockBuffer?

    CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer,
                                                            bufferListSizeNeededOut: nil,
                                                            bufferListOut: &abl,
                                                            bufferListSize: MemoryLayout<AudioBufferList>.size,
                                                            blockBufferAllocator: nil,
                                                            blockBufferMemoryAllocator: nil,
                                                            flags: 0,
                                                            blockBufferOut: &blockBuffer)

    let buffers = UnsafeMutableAudioBufferListPointer(&abl)

    var data = Data()
    for audioBuffer in buffers {
        if let frame = audioBuffer.mData?.assumingMemoryBound(to: UInt8.self) {
            data.append(frame, count: Int(audioBuffer.mDataByteSize))
        }
    }
    return data
}

func sampleBuffer(from data: Data) -> CMSampleBuffer? {
    var buffer = data.bytes
    var sampleBuffer: CMSampleBuffer?
    var audioFormat = AudioStreamBasicDescription(mSampleRate: 44100,
                                                  mFormatID: kAudioFormatLinearPCM,
                                                  mFormatFlags: 0xe,
                                                  mBytesPerPacket: 2,
                                                  mFramesPerPacket: 1,
                                                  mBytesPerFrame: 2,
                                                  mChannelsPerFrame: 1,
                                                  mBitsPerChannel: 16,
                                                  mReserved: 0)

    var format: CMAudioFormatDescription?
    var status = CMAudioFormatDescriptionCreate(allocator: kCFAllocatorDefault,
                                                asbd: &audioFormat,
                                                layoutSize: 0,
                                                layout: nil,
                                                magicCookieSize: 0,
                                                magicCookie: nil,
                                                extensions: nil,
                                                formatDescriptionOut: &format)

    var timing = CMSampleTimingInfo(duration: CMTimeMake(value: 1, timescale: 44100),
                                    presentationTimeStamp: .zero,
                                    decodeTimeStamp: .invalid)

    status = CMSampleBufferCreate(allocator: kCFAllocatorDefault,
                                  dataBuffer: nil,
                                  dataReady: false,
                                  makeDataReadyCallback: nil,
                                  refcon: nil,
                                  formatDescription: format,
                                  sampleCount: buffer.count / 2, // mBytesPerFrame = 2
                                  sampleTimingEntryCount: 1,
                                  sampleTimingArray: &timing,
                                  sampleSizeEntryCount: 0,
                                  sampleSizeArray: nil,
                                  sampleBufferOut: &sampleBuffer)
    guard status == noErr else { return nil }

    var abl = AudioBufferList(mNumberBuffers: 1, mBuffers: (AudioBuffer(mNumberChannels: 1, mDataByteSize: UInt32(buffer.count), mData: &buffer)))
    status = CMSampleBufferSetDataBufferFromAudioBufferList(sampleBuffer!,
                                                            blockBufferAllocator: kCFAllocatorDefault,
                                                            blockBufferMemoryAllocator: kCFAllocatorDefault,
                                                            flags: 0,
                                                            bufferList: &abl)
    guard status == noErr else { return nil }
    return sampleBuffer
}

"Cannot use inout expression here; argument 'mData' must be a pointer that outlives the call to 'init(mNumberChannels:mDataByteSize:mData:)'"