Question

所以我在这里根据一些帖子拼凑了一些记录音频的例程。我引用的帖子是here和here，以及阅读他们引用的网站。

我的设置：我有一个现有的AUGraph :(几个AUSamplers - ＆gt; Mixer - ＆gt; RemoteIO）。 AUSamplers连接到MusicPlayer实例中的曲目。一切正常但是我想添加录音。

录音工作正常但是得到的.caf音高/速度变慢+音质不好。我指定的格式一定有问题吗？

有人可以注意这一点并告诉我我在哪里设置错误的格式吗？

编辑：这可能是立体声/单声道问题吗？我的意思是用单声道录音。

我将RemoteIO实例上的流格式设置为：

   AudioStreamBasicDescription audioFormat;

audioFormat.mSampleRate         = 44100.00;
audioFormat.mFormatID           = kAudioFormatLinearPCM;
audioFormat.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audioFormat.mFramesPerPacket    = 1;
audioFormat.mChannelsPerFrame   = 1;
audioFormat.mBitsPerChannel     = 16;
audioFormat.mBytesPerPacket     = 2;
audioFormat.mBytesPerFrame      = 2;

// Apply format
result = AudioUnitSetProperty(ioUnit, 
                              kAudioUnitProperty_StreamFormat, 
                              kAudioUnitScope_Output, 
                              kInputBus, 
                              &audioFormat, 
                              sizeof(audioFormat));

然后从按钮操作中创建一个fileRef并将renderCallback附加到RemoteIO实例：

- (void)startRecording
{

OSStatus result;

AudioStreamBasicDescription audioFormat;

audioFormat.mSampleRate         = 44100.00;
audioFormat.mFormatID           = kAudioFormatLinearPCM;
audioFormat.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audioFormat.mFramesPerPacket    = 1;
audioFormat.mChannelsPerFrame   = 1;
audioFormat.mBitsPerChannel     = 16;
audioFormat.mBytesPerPacket     = 2;
audioFormat.mBytesPerFrame      = 2;

NSArray  *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *destinationFilePath = [[NSString alloc] initWithFormat: @"%@/output.caf", documentsDirectory];
CFURLRef destinationURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, 
                                                        (__bridge CFStringRef)destinationFilePath, 
                                                        kCFURLPOSIXPathStyle, 
                                                        false);

result = ExtAudioFileCreateWithURL(destinationURL, 
                                   kAudioFileWAVEType, 
                                   &audioFormat, 
                                   NULL, 
                                   kAudioFileFlags_EraseFile, 
                                   &extAudioFileRef);  

CFRelease(destinationURL);
NSAssert(result == noErr, @"Couldn't create file for writing");

result = ExtAudioFileSetProperty(extAudioFileRef, 
                                 kExtAudioFileProperty_ClientDataFormat, 
                                 sizeof(AudioStreamBasicDescription), 
                                 &audioFormat);

NSAssert(result == noErr, @"Couldn't create file for format");

result =  ExtAudioFileWriteAsync(extAudioFileRef, 0, NULL);
NSAssert(result == noErr, @"Couldn't initialize write buffers for audio file");   


printf("Adding render to remoteIO     \n");
result = AudioUnitAddRenderNotify(ioUnit, renderCallback, (__bridge void*)self);
if (result) {[self printErrorMessage: @"AudioUnitAddRenderNotify" withStatus: result]; return;}
 }

最后在我的rendercallback中，我在postRender阶段写出了数据：

static OSStatus renderCallback (void *                       inRefCon,
                            AudioUnitRenderActionFlags * ioActionFlags,
                            const AudioTimeStamp *       inTimeStamp,
                            UInt32                       inBusNumber,
                            UInt32                       inNumberFrames,
                            AudioBufferList *            ioData) 
{

OSStatus result;
   if (*ioActionFlags == kAudioUnitRenderAction_PostRender){
    double timeInSeconds = inTimeStamp->mSampleTime / kSampleRate;
    printf("%fs inBusNumber: %lu inNumberFrames: %lu \n", timeInSeconds, inBusNumber, inNumberFrames);

    MusicPlayerController* THIS = (__bridge MusicPlayerController *)inRefCon;

   result =  ExtAudioFileWriteAsync(THIS->extAudioFileRef, inNumberFrames, ioData);
    if(result) printf("ExtAudioFileWriteAsync %ld \n", result);

  }

return noErr; 
}

Answer 1

好的 - 找到了解决这个问题的一些代码 - 虽然我不完全理解为什么。

我将RemoteIO输出流和ExtFileRef的mBitsPerChannel设置为16。结果放慢了速度。沙哑的音频。将ExtFileRef mBitsPerChannel设置为32加上添加kAudioFormatFlagsNativeEndian标志可以解决问题：.caf音频非常完美（将RemoteIO输出流设置保留原样）。

但是，设置RemoteIO输出流设置以匹配我的新设置也可以。所以我很困惑。只要AudioStreamBasicDescription设置对于RemoteIO实例和ExtFileRef是对称的，这不应该工作吗？

无论如何......工作设置如下。

size_t bytesPerSample = sizeof (AudioUnitSampleType);

AudioStreamBasicDescription audioFormat;
audioFormat.mSampleRate= graphSampleRate;
audioFormat.mFormatID=kAudioFormatLinearPCM;
audioFormat.mFormatFlags=kAudioFormatFlagsNativeEndian|kAudioFormatFlagIsSignedInteger|kAudioFormatFlagIsPacked;
audioFormat.mBytesPerPacket=bytesPerSample;
audioFormat.mBytesPerFrame=bytesPerSample;
audioFormat.mFramesPerPacket=1;
audioFormat.mChannelsPerFrame=1;
audioFormat.mBitsPerChannel= 8 * bytesPerSample;
audioFormat.mReserved=0;

从RemoteIO录制：得到的.caf音高移位慢+失真

1 个答案: