Question

我在这里遇到AVAssetReader的问题，从iPod库中获取样本并通过Audio Queue进行流式传输。我无法找到任何这样的例子，所以我尝试实现自己的，但似乎不知何故，AssetReader被“搞砸”在音频队列的回调函数中。具体来说，它在执行copyNextSampleBuffer时失败，即它还没有完成时返回null。我已经确定指针存在，所以如果有人可以提供帮助就会很棒。

下面是我使用过的回调函数代码。当AudioQueue回调未调用时，此回调函数“有效”。

    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

我遇到了同样神秘的错误。果然，“设置”音频会话使得错误消失了。这就是我设置音频会话的方式。

- (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);
}

Answer 2

来自音频会话编程指南，AVAudioSessionCategoryAmbient：

此类别允许在应用播放音频时播放来自iPod，Safari和其他内置应用程序的音频。

使用AVAssetReader可能使用iOS的硬件解码器，它会阻止使用AudioQueue。设置AVAudioSessionCategoryAmbient意味着音频以软件呈现，允许两者同时工作 - 但是，这会对性能/电池寿命产生影响。（请参阅“类别如何影响编码和解码”下的Audio Session Programming Guide）。

Answer 3

好的我已经以某种方式解决了这个奇怪的错误......显然这是因为音频会话没有正确设置。谈论缺乏这方面的文件...

AVAssetReader和音频队列流问题

3 个答案: