无法使用AVSampleBufferAudioRenderer播放ACC流

问题描述

我正在开发一个接收带有视频和音频数据包流的应用程序。我能够解码视频并使用AVSampleBufferDisplayLayer播放它。 （可以在here中找到代码）但是我已经花了一个多星期的时间来解码音频。在流的开头，我收到这样的音频描述-> sampleRate=48000，channelCount=1和profileLevel=2。然后，我不断接收ACC数据包，并尝试在ACC数据包中解码。就像我对待视频数据包一样。首先，我创建AudioStreamBasicDescription，CMAudioFormatDescription，并设置audioRenderer和audioRendererSynchoronizer。

   class AudioDecoderPlayer: NSObject {
  private var audioRenderer = AVSampleBufferAudioRenderer()
  private var audioRendererSynchoronizer = AVSampleBufferRenderSynchronizer()
  private let serializationQueue = DispatchQueue(label: "sample.buffer.player.serialization.queue")

  private var audioStreamBasicDescription: AudioStreamBasicDescription
  private var formatDescription: CMAudioFormatDescription?

  private var outputQueue: AudioQueueRef?

  var sampleBuffers: [CMSampleBuffer] = []
  
  let sampleRate: Double
  let channels: Int

  init(sampleRate: Double = 48000,channels: Int = 1,profileLevel: Int = 2) {

    self.sampleRate = sampleRate
    self.channels = channels
    
    let uChannels = UInt32(channels)
    let channelBytes = UInt32(MemoryLayout<Int16>.size)
    let bytesPerFrame = uChannels * channelBytes


    self.audioStreamBasicDescription = AudioStreamBasicDescription(
      mSampleRate: Float64(sampleRate),mFormatID: kAudioFormatMPEG4AAC,mFormatFlags: AudioFormatFlags(profileLevel),mBytesPerPacket: bytesPerFrame,mFramesPerPacket: 1,mBytesPerFrame: bytesPerFrame,mChannelsPerFrame: uChannels,mBitsPerChannel: channelBytes * 8,mReserved: 0
    )

    super.init()
    
    let status = CMAudioFormatDescriptionCreate(allocator: kCFAllocatorDefault,asbd: &audioStreamBasicDescription,layoutSize: 0,layout: nil,magicCookieSize: 0,magicCookie: nil,extensions: nil,formatDescriptionOut: &formatDescription)

    if status != noErr {
      fatalError("unable to create audio format description")
    }
    
    
    audioRendererSynchoronizer.addRenderer(audioRenderer)
    subscribeToAudioRenderer()
    startPlayback()
  }
  
  func subscribeToAudioRenderer() {
    audioRenderer.requestMediaDataWhenReady(on: serializationQueue,using: { [weak self] in
      guard let strongSelf = self else {
        return
      }
      
      while strongSelf.audioRenderer.isReadyForMoreMediaData {
        if let sampleBuffer = strongSelf.nextSampleBuffer() {
          strongSelf.audioRenderer.enqueue(sampleBuffer)
        }
      }
    })
  }
  
  func startPlayback() {
    serializationQueue.async {
      if self.audioRendererSynchoronizer.rate != 1 {
        self.audioRendererSynchoronizer.rate = 1
        self.audioRenderer.volume = 1.0
      }
    }
  }
  
  func nextSampleBuffer() -> CMSampleBuffer? {
    guard sampleBuffers.count > 0 else {
      return nil
    }
    
    let sampleBuffer = sampleBuffers.first
    sampleBuffers.remove(at: 0)
    
    return sampleBuffer
  }

这就是我的解码功能的样子

  func decodeAudioPacket(data: Data) {
    let headerValue = UInt32(data.count)

    //add data lenght at the beginning
    var sizedData = withUnsafeBytes(of: headerValue.bigEndian) { Data($0) }
    sizedData.append(data)

    let blockBuffer = sizedData.toCMBlockBuffer()

    // Outputs from CMSampleBufferCreate
    var sampleBuffer: CMSampleBuffer?

    let result = CMAudioSampleBufferCreateReadyWithPacketDescriptions(
      allocator: kCFAllocatorDefault,dataBuffer: blockBuffer,formatDescription: formatDescription!,sampleCount: 1,presentationTimeStamp: CMTime(value: 1,timescale: Int32(sampleRate)),packetDescriptions: nil,sampleBufferOut: &sampleBuffer)


    if result != noErr {
      fatalError("CMSampleBufferCreate() failed")
    }

    sampleBuffers.append(sampleBuffer!)
  }

我发现requestMediaDataWhenReady仅被调用一次，这表明未在播放声音，但我不明白为什么。我可以通过编辑WWDC 2017会话509中的代码来使其工作，但仍然没有声音在播放。 （可以在here中找到代码）我也尝试过将各种解决方案与AudioQueue一起使用，但是没有成功。 （由于某些原因，从未调用过来自AudioFileStreamOpen的回调）（可以找到here和here的代码）。但是我宁愿使用AVSampleBufferAudioRenderer来解决它，因为我认为它应该更容易，而且我还想使用AVSampleBufferAudioRendererSynchronizer来将视频与音频同步。

任何关于我做错事的建议都会受到赞赏。

谢谢

解决方法

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