iphone - 通过 AVAssetReader 读取音频样本

Question

如何通过 AVAssetReader 读取音频样本？我找到了使用 AVAssetReader 进行复制或混合的示例，但这些循环始终由 AVAssetWriter 循环控制。是否可以只创建一个 AVAssetReader 并读取它，获取每个样本并将每个音频样本的 int32 放入数组中？

谢谢。

Answer 1

要扩展@amrox 的答案，您可以从 CMBlockBufferRef 获取 AudioBufferList，例如

CMItemCount numSamplesInBuffer = CMSampleBufferGetNumSamples(buffer);

AudioBufferList audioBufferList;

CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
      buffer,
      NULL,
      &audioBufferList,
      sizeof(audioBufferList),
      NULL,
      NULL,
      kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment,
      &buffer
    );

for (int bufferCount=0; bufferCount < audioBufferList.mNumberBuffers; bufferCount++) {
  SInt16* samples = (SInt16 *)audioBufferList.mBuffers[bufferCount].mData;
  for (int i=0; i < numSamplesInBuffer; i++) {
    // amplitude for the sample is samples[i], assuming you have linear pcm to start with
  }
}

//Release the buffer when done with the samples 
//(retained by CMSampleBufferGetAudioBufferListWithRetainedblockBuffer)
CFRelease(buffer);