Question

我使用ExtAudioFileWriteAsync在使用设备录制时编写音频文件，但是一旦我完成录制，我尝试用ExtAudioFileRead函数读取它，我得到的样本与我写的样本不一样...任何人都知道为什么这样做发生？

写作：

self.audioManager.inputBlock = ^(float *data, UInt32 numFrames, UInt32 numChannels) {
  for (int i = 0; i < numFrames*numChannels; i++) {
        printf("write*%f\n", data[i]);
  }

  UInt32 numIncomingBytes = numFrames*numChannels*sizeof(float);
  UInt32 *outputBuffer =(UInt32*)malloc(numIncomingBytes);
  memcpy(outputBuffer, recordedData, numIncomingBytes);

  AudioBufferList outgoingAudio;
  outgoingAudio.mNumberBuffers = 1;
  outgoingAudio.mBuffers[0].mNumberChannels = numChannels;
  outgoingAudio.mBuffers[0].mDataByteSize = numIncomingBytes;
  outgoingAudio.mBuffers[0].mData = self.outputBuffer;

  if( 0 == pthread_mutex_trylock( &outputAudioFileLock ) ) 
  {       
      ExtAudioFileWriteAsync(outputFile, numFrames, &outgoingAudio);
  }
  pthread_mutex_unlock( &outputAudioFileLock );    
};
[self.audioManager play];

阅读：

UInt32 *outputBuffer = (UInt32 *)malloc(numFrames*numChannels*sizeof(float));

AudioBufferList convertedData;
convertedData.mNumberBuffers = 1;
convertedData.mBuffers[0].mNumberChannels = numChannels;
convertedData.mBuffers[0].mDataByteSize = numFrames*numChannels*sizeof(float);
convertedData.mBuffers[0].mData = outputBuffer;

NSMutableArray *samplesArray = [[NSMutableArray alloc]init];
while (numFrames > 0) {
    ExtAudioFileRead(inputFile, &numFrames, &convertedData);
    if (numFrames > 0)  {
        AudioBuffer audioBuffer = convertedData.mBuffers[0];
        float *samples = (float *)audioBuffer.mData;
        for (int i = 0; i < frameCount*numChannels; i++) {
            printf("read*%f\n", samples[i]);
        }
    }
}

顺便说一下，我正在使用Novocaine项目来获取设备音频。我可以使用Novocaine代码或任何其他播放器重现已保存的音频。

编写ExtAudioFileRef输出时：

 ExtAudioFileCreateWithURL(audioFileRef, kAudioFileM4AType,   &outputFileDesc, NULL, kAudioFileFlags_EraseFile, &outputFile);

其中outputFileDesc是

AudioStreamBasicDescription outputFileDesc = {44100.0，kAudioFormatMPEG4AAC，0,0,1024,0，thisNumChannels，0,0}; outputFileDesc.mFormatFlags = kAudioFormatFlagIsBigEndian | kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;

阅读ExtAudioFileRef inputFile：

ExtAudioFileOpenURL(audioFileRef, &inputFile):

在两种情况下（写作和阅读）都采用相同的格式：

AudioStreamBasicDescription outputFormat;
_outputFormat.mSampleRate = self.samplingRate;
_outputFormat.mFormatID = kAudioFormatLinearPCM;
_outputFormat.mFormatFlags = kAudioFormatFlagIsFloat;
_outputFormat.mBytesPerPacket = 4*self.numChannels;
_outputFormat.mFramesPerPacket = 1;
_outputFormat.mBytesPerFrame = 4*self.numChannels;
_outputFormat.mChannelsPerFrame = self.numChannels;
_outputFormat.mBitsPerChannel = 32;


ExtAudioFileSetProperty(outputFile, kExtAudioFileProperty_ClientDataFormat, sizeof(AudioStreamBasicDescription), &_outputFormat);


 ExtAudioFileSetProperty(inputFile, kExtAudioFileProperty_ClientDataFormat, sizeof(AudioStreamBasicDescription), &_outputFormat);

顺便说一下，即使读取样本不等于写入样本，两个信号的平均值也非常相似。但我不完全明白为什么不完全平等！

知道我做错了吗？

Answer 1

听起来有一个或两个ExtaudioFileRefs的隐式格式转换，你会看到转换后的不同样本。您有三种格式：audio_in_format，file_format和audio_out_format。如果audio_in_format与file_format不同，则写入ExtAudioFileRef将创建一个音频转换器，以便在写入磁盘之前将输入音频转换为file_format。如果file_format与audio_out_format不同，读取ExtAudioFileRef也会创建一个转换器。

观点：你把你的写作ExtAudioFileRef命名为“outputFile”，并且读取ExtAudioFileRef“inputFile”是令人困惑的。我会使用像audioWriter和audioReader这样的东西。

使用扩展音频文件编写和读取音频文件

1 个答案: