iphone - AVAssetReader 和音频队列流问题

Question

我在使用 AVAssetReader 时遇到问题，无法从 iPod 库获取样本并通过音频队列进行流式传输。我无法找到任何这样的示例，因此我尝试实现自己的示例，但似乎 AssetReader 在音频队列的回调函数处“搞砸了”。具体来说，当它执行 copyNextSampleBuffer 时，它会失败，即，当它尚未完成时，它会返回 null。我已经确保指针存在，因此如果有人能提供帮助，那就太好了。

下面是我使用过的回调函数代码。当 AudioQueue 回调未调用此回调函数时，该函数会“起作用”。

    static void HandleOutputBuffer (
        void                *playerStateH,
        AudioQueueRef       inAQ,
        AudioQueueBufferRef inBuffer
        ) {

 AQPlayerState *pplayerState = (AQPlayerState *) playerStateH;
 //if (pplayerState->mIsRunning == 0) return;    



 UInt32 bytesToRead = pplayerState->bufferByteSize;
 [[NSNotificationCenter defaultCenter] postNotificationName:NOTIF_callsample object:nil];


 float * inData =(float *) inBuffer->mAudioData;
 int offsetSample = 0;
 //Loop until finish reading from the music data
 while (bytesToRead) {

  /*THIS IS THE PROBLEMATIC LINE*/
  CMSampleBufferRef sampBuffer = [pplayerState->assetWrapper getNextSampleBuffer]; //the assetreader getting nextsample with copyNextSampleBuffer

  if (sampBuffer == nil) {
   NSLog(@"No more data to read from");
 //  NSLog(@"aro status after null %d",[pplayerState->ar status]);
   AudioQueueStop (
       pplayerState->mQueue,
       false
       );
   pplayerState->mIsRunning = NO;

   return;
  }

  AudioBufferList  audioBufferList;
  CMBlockBufferRef blockBuffer;
  CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampBuffer, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
  AudioBuffer audioBuffer = audioBufferList.mBuffers[0];
  memcpy(inData + (2*offsetSample),audioBuffer.mData,audioBuffer.mDataByteSize);
  bytesToRead = bytesToRead - audioBuffer.mDataByteSize;
  offsetSample = offsetSample + audioBuffer.mDataByteSize/8;



 }
 inBuffer->mAudioDataByteSize = offsetSample*8;

 AudioQueueEnqueueBuffer ( 
        pplayerState->mQueue,
        inBuffer,
        0,
        0
        );


}

Answer 1

我也遇到了同样令人困惑的错误。果然，“设置” Audio Session 使错误消失了。这就是我设置 Audio Session 的方式。

- (void)setupAudio {
    [[AVAudioSession sharedInstance] setDelegate:self];
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient error:nil];
    NSError *activationError = nil;
    [[AVAudioSession sharedInstance] setActive: YES error:&activationError];

    NSLog(@"setupAudio ACTIVATION ERROR IS %@", activationError);
    [[AVAudioSession sharedInstance] setPreferredIOBufferDuration:0.1 error:&activationError];
    NSLog(@"setupAudio BUFFER DURATION ERROR IS %@", activationError);
}