通过 AVAssetReader 读取音频样本

问题描述

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 并通读它，获取每个样本并将每个音频样本的 int32 扔到一个数组中?

How do you read audio samples via AVAssetReader? I've found examples of duplicating or mixing using AVAssetReader, but those loops are always controlled by the AVAssetWriter loop. Is it possible just to create an AVAssetReader and read through it, getting each sample and throwing the int32 of each audio sample into an array?

谢谢.

推荐答案

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

To expand on @amrox's answer, you can get an AudioBufferList from the CMBlockBufferRef, e.g.

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);

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