AVCaptureOutput通过TPCircularBuffer到音频单元回调

Question

我正在构建AUGraph，并尝试通过AVCaptureAudioDataOutput委托方法从输入设备获取音频。

AVCaptureSession的使用是此处解释的问题的结果 。 我成功地通过CARingbuffer通过这种方法构建了一个音频播放，如《 学习核心音频 》一书中所述。 但是，从CARingbuffer中获取数据意味着要提供有效的采样时间，并且当我停止AVCaptureSession时，来自AVCaptureOutput和单元输入回调的采样时间将不再同步。 因此，根据我已阅读的内容，我现在尝试使用迈克尔·泰森（Michael Tyson）的TPCircularBuffer ，它似乎很棒。 但是，即使找到了一些示例，我也无法从中获得一些音频（或仅有裂纹）。

我的图看起来像这样：

AVCaptureSession -> callback -> AUConverter -> ... -> HALOutput

这是我的AVCaptureOutput方法的代码

- (void) captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{

CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer);
const AudioStreamBasicDescription *sampleBufferASBD = CMAudioFormatDescriptionGetStreamBasicDescription(formatDescription);

if (kAudioFormatLinearPCM != sampleBufferASBD->mFormatID) {

    NSLog(@"Bad format or bogus ASBD!");
    return;

}

if ((sampleBufferASBD->mChannelsPerFrame != _audioStreamDescription.mChannelsPerFrame) || (sampleBufferASBD->mSampleRate != _audioStreamDescription.mSampleRate)) {

    _audioStreamDescription = *sampleBufferASBD;
    NSLog(@"sample input format changed");

}




CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer,
                                                        NULL,
                                                        _currentInputAudioBufferList,
                                                        CAAudioBufferList::CalculateByteSize(_audioStreamDescription.mChannelsPerFrame),
                                                        kCFAllocatorSystemDefault,
                                                        kCFAllocatorSystemDefault,
                                                        kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment,
                                                        &_blockBufferOut);


TPCircularBufferProduceBytes(&_circularBuffer, _currentInputAudioBufferList->mBuffers[0].mData, _currentInputAudioBufferList->mBuffers[0].mDataByteSize);

和render回调：

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

ozAVHardwareInput *hardWareInput = (ozAVHardwareInput *)inRefCon;
TPCircularBuffer circularBuffer = [hardWareInput circularBuffer];

Float32 *targetBuffer = (Float32 *)ioData->mBuffers[0].mData;

int32_t availableBytes;
TPCircularBufferTail(&circularBuffer, &availableBytes);
UInt32 dataSize = ioData->mBuffers[0].mDataByteSize;

if (availableBytes > ozAudioDataSizeForSeconds(3.)) {

    // There is too much audio data to play -> clear buffer & mute output
    TPCircularBufferClear(&circularBuffer);

    for(UInt32 i = 0; i < ioData->mNumberBuffers; i++)
        memset(ioData->mBuffers[i].mData, 0, ioData->mBuffers[i].mDataByteSize);

} else if (availableBytes > ozAudioDataSizeForSeconds(0.5)) {

    // SHOULD PLAY
    Float32 *cbuffer = (Float32 *)TPCircularBufferTail(&circularBuffer, &availableBytes);
    int32_t min = MIN(dataSize, availableBytes);

    memcpy(targetBuffer, cbuffer, min);
    TPCircularBufferConsume(&circularBuffer, min);
    ioData->mBuffers[0].mDataByteSize = min;

} else {

    // No data to play -> mute output
    for(UInt32 i = 0; i < ioData->mNumberBuffers; i++)
        memset(ioData->mBuffers[i].mData, 0, ioData->mBuffers[i].mDataByteSize);
}

return noErr;

}

TPCIrcularBuffer被提供了AudioBufferList，但没有输出，或者有时只是裂缝。

我究竟做错了什么 ？

Answer 1

音频单元渲染回调应始终返回样本的inNumberFrames。 检查以查看回调返回的数据量。