RemoteIO 录制的音频文件为静音或 4KB

Posted 2023-02-23

【中文标题】RemoteIO 录制的音频文件为静音或 4KB

【英文标题】：RemoteIO recorded audio file is either silent or 4KB

【发布时间】：2012-11-21 20:45:30

【问题描述】：

我正在成功使用 RemoteIO 对来自麦克风的传入音频流执行分析。不过，我似乎无法将文件写入磁盘。我已经阅读了一些问题：

Example of saving audio from RemoteIO?, AudioBufferList contents in remoteIO audio unit playback callback, Recording to AAC from RemoteIO: data is getting written but file unplayable Recording from RemoteIO: resulting .caf is pitch shifted slower + distorted

并尝试在那里实施建议：除非它们不起作用。调用 ExtAudioFileWriteAsync 的正确位置在哪里，如何设置？

【参考方案1】：

除了 RemoteIO 本身的设置过程（相当艰巨但由Apple's example code 更好地涵盖）之外，洞察的关键点是：

使用与我最初设置流时相同的AudiostreamBasicDescription (*audioFormat)。根据其他问题和帖子，我不知道我花了多长时间尝试设置一个参数略有不同的新参数。只需从我的 ivar 中引用流属性就足够了。 设置一个“isRecording”布尔值，这样您就可以打开和关闭写入文件，而无需拆除并重新设置您的 RemoteIO 会话 在recordingCallback，嗯，回调中写入文件是可以的，但是异步执行。很多信息都在谈论在playbackCallback 中执行此操作或设置第三个audioFileWriteCallback。这导致了无声文件或 4KB（即空）文件。不要这样做。 另外，请务必使用传入回调的 ioData 的副本

在recordingCallback 之后AudioUnitRender 变成bufferList：

    AudioDeviceManager* THIS = (__bridge AudioDeviceManager *)inRefCon;
    if (THIS->isRecording) 
      ExtAudioFileWriteAsync(THIS->extAudioFileRef, inNumberFrames, bufferList);
    

启动和停止录制功能，供参考：

-(void)startRecording

  NSArray  *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *documentsDirectory = [paths objectAtIndex:0];
  NSString *destinationFilePath = [documentsDirectory stringByAppendingPathComponent:kAudioFileName];
  CFURLRef destinationURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)destinationFilePath, kCFURLPOSIXPathStyle, false);

  OSStatus status;

  // create the capture file
  status = ExtAudioFileCreateWithURL(destinationURL, kAudioFileWAVEType, &audioFormat, NULL, kAudioFileFlags_EraseFile, &extAudioFileRef);
  if (status) NSLog(@"Error creating file with URL: %ld", status);

 // use the same "audioFormat" AudioStreamBasicDescription we used to set up RemoteIO in the first place
  status = ExtAudioFileSetProperty(extAudioFileRef, kExtAudioFileProperty_ClientDataFormat, sizeof(AudioStreamBasicDescription), &audioFormat);

  ExtAudioFileSeek(extAudioFileRef, 0);
  ExtAudioFileWrite(extAudioFileRef, 0, NULL);

  isRecording = YES;

- (void)stopRecording 

  isRecording = NO;
  OSStatus status = ExtAudioFileDispose(extAudioFileRef);
  if (status) printf("ExtAudioFileDispose %ld \n", status);

就是这样！