convertCMSampleBuffer.swift

func convertCMSampleBuffer(from pcmBuffer: AVAudioPCMBuffer) -> CMSampleBuffer? {
    let bufferList = pcmBuffer.audioBufferList
    let asbd = pcmBuffer.format.streamDescription

    var sampleBuffer: CMSampleBuffer!
    var formatDescription: CMFormatDescription!

    var status = CMAudioFormatDescriptionCreate(allocator: kCFAllocatorDefault,
                                            asbd: asbd,
                                            layoutSize: 0,
                                            layout: nil,
                                            magicCookieSize: 0,
                                            magicCookie: nil,
                                            extensions: nil,
                                            formatDescriptionOut: &formatDescription)
    guard status == kCMBlockBufferNoErr else {
        return nil
    }
    var timing = CMSampleTimingInfo(duration: CMTime(value: 1, timescale: CMTimeScale(asbd.pointee.mSampleRate)),
                                    presentationTimeStamp: CMTime.zero,
                                    decodeTimeStamp: CMTime.invalid)

    status = CMSampleBufferCreate(allocator: kCFAllocatorDefault,
                                  dataBuffer: nil,
                                  dataReady: false,
                                  makeDataReadyCallback: nil,
                                  refcon: nil,
                                  formatDescription: formatDescription,
                                  sampleCount: CMItemCount(pcmBuffer.frameLength),
                                  sampleTimingEntryCount: 1,
                                  sampleTimingArray: &timing,
                                  sampleSizeEntryCount: 0,
                                  sampleSizeArray: nil,
                                  sampleBufferOut: &sampleBuffer)
    guard status == kCMBlockBufferNoErr else {
        return nil
    }
    status = CMSampleBufferSetDataBufferFromAudioBufferList(sampleBuffer,
                                                            blockBufferAllocator: kCFAllocatorDefault,
                                                            blockBufferMemoryAllocator: kCFAllocatorDefault,
                                                            flags: 0,
                                                            bufferList: bufferList)
    guard status == kCMBlockBufferNoErr else {
        return nil
    }

    return sampleBuffer
}