ios - RemoteIO 录制的音频文件为静音或 4KB

Question

我正在成功使用 RemoteIO 对来自麦克风的传入音频流进行分析。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

并试图在那里实现这些建议:除非它们不起作用。调用 ExtAudioFileWriteAsync 的正确位置在哪里，如何设置？

Answer 1

除了 RemoteIO 本身的(相当艰巨但更好地由 Apple's example code 覆盖)设置过程之外，洞察的关键点是:

使用相同的AudioStreamBasicDescription ( *audioFormat ) 我一开始用来设置流。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” bool 值，这样您就可以打开和关闭写入文件，而无需拆除和重新设置您的 RemoteIO session

可以写入 recordingCallback 中的文件，嗯，回调，但异步执行。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。

此外，请务必使用传入回调

的 ioData 的副本。

在 recordingCallback在 AudioUnitRender 之后进入 bufferList :

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

开始和停止录音功能，供引用:


-(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!