音频CMSampleBuffer的深层复制

Question

我正在尝试创建一个CMSampleBuffer的副本,该副本由captureOutput在a中返回AVCaptureAudioDataOutputSampleBufferDelegate.

我遇到的问题是,captureOutput:didOutputSampleBuffer:fromConnection:在我保留CFArray了很长一段时间之后,来自委托方法的框架被丢弃了.

显然,我需要创建传入缓冲区的深层副本以供进一步处理.我也知道CMSampleBufferCreateCopy只会创建浅拷贝.

SO上提出的相关问题很少:

• 从CMSampleBuffer中提取数据以创建深层副本
• 在Swift中创建CMSampleBuffer的副本返回OSStatus -12743(无效的媒体格式)
• CMImageBuffer或CVImageBuffer的深层副本

但它们都没有帮助我使用12个参数正确使用CMSampleBufferCreate函数:

  CMSampleBufferRef copyBuffer;

  CMBlockBufferRef data = CMSampleBufferGetDataBuffer(sampleBuffer);
  CMFormatDescriptionRef formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer);
  CMItemCount itemCount = CMSampleBufferGetNumSamples(sampleBuffer);

  CMTime duration = CMSampleBufferGetDuration(sampleBuffer);
  CMTime presentationStamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
  CMSampleTimingInfo timingInfo;
  timingInfo.duration = duration;
  timingInfo.presentationTimeStamp = presentationStamp;
  timingInfo.decodeTimeStamp = CMSampleBufferGetDecodeTimeStamp(sampleBuffer);


  size_t sampleSize = CMBlockBufferGetDataLength(data);
  CMBlockBufferRef sampleData;

  if (CMBlockBufferCopyDataBytes(data, 0, sampleSize, &sampleData) != kCMBlockBufferNoErr) {
    VLog(@"error during copying sample buffer");
  }

  // Here I tried data and sampleData CMBlockBuffer instance, but no success
  OSStatus status = CMSampleBufferCreate(kCFAllocatorDefault, data, isDataReady, nil, nil, formatDescription, itemCount, 1, &timingInfo, 1, &sampleSize, &copyBuffer);

  if (!self.sampleBufferArray)  {
    self.sampleBufferArray = CFArrayCreateMutable(NULL, 0, &kCFTypeArrayCallBacks);
    //EXC_BAD_ACCESS crash when trying to add sampleBuffer to the array
    CFArrayAppendValue(self.sampleBufferArray, copyBuffer);
  } else  {
    CFArrayAppendValue(self.sampleBufferArray, copyBuffer);
  }

你如何深度复制音频CMSampleBuffer？随意在答案中使用任何语言(swift/objective-c).

Answer 1

这是我最终实施的工作解决方案.我将此代码段发送给Apple Developer Technical支持,并要求他们检查是否是正确的方法来复制传入的样本缓冲区.基本思想是复制AudioBufferList,然后创建一个CMSampleBuffer并设置AudioBufferList为此示例.

AudioBufferList audioBufferList;
CMBlockBufferRef blockBuffer;
//Create an AudioBufferList containing the data from the CMSampleBuffer,
//and a CMBlockBuffer which references the data in that AudioBufferList.
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
NSUInteger size = sizeof(audioBufferList);
char buffer[size];

memcpy(buffer, &audioBufferList, size);
//This is the Audio data.
NSData *bufferData = [NSData dataWithBytes:buffer length:size];

const void *copyBufferData = [bufferData bytes];
copyBufferData = (char *)copyBufferData;

CMSampleBufferRef copyBuffer = NULL;
OSStatus status = -1;

/* Format Description */

AudioStreamBasicDescription audioFormat = *CMAudioFormatDescriptionGetStreamBasicDescription((CMAudioFormatDescriptionRef) CMSampleBufferGetFormatDescription(sampleBuffer));

CMFormatDescriptionRef format = NULL;
status = CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &audioFormat, 0, nil, 0, nil, nil, &format);

CMFormatDescriptionRef formatdes = NULL;
status = CMFormatDescriptionCreate(NULL, kCMMediaType_Audio, 'lpcm', NULL, &formatdes);
if (status != noErr)
{
  NSLog(@"Error in CMAudioFormatDescriptionCreator");
  CFRelease(blockBuffer);
  return;
}

/* Create sample Buffer */
CMItemCount framesCount = CMSampleBufferGetNumSamples(sampleBuffer);
CMSampleTimingInfo timing   = {.duration= CMTimeMake(1, 44100), .presentationTimeStamp= CMSampleBufferGetPresentationTimeStamp(sampleBuffer), .decodeTimeStamp= CMSampleBufferGetDecodeTimeStamp(sampleBuffer)};

status = CMSampleBufferCreate(kCFAllocatorDefault, nil , NO,nil,nil,format, framesCount, 1, &timing, 0, nil, &copyBuffer);

if( status != noErr) {
  NSLog(@"Error in CMSampleBufferCreate");
  CFRelease(blockBuffer);
  return;
}

/* Copy BufferList to Sample Buffer */
AudioBufferList receivedAudioBufferList;
memcpy(&receivedAudioBufferList, copyBufferData, sizeof(receivedAudioBufferList));

//Creates a CMBlockBuffer containing a copy of the data from the
//AudioBufferList.
status = CMSampleBufferSetDataBufferFromAudioBufferList(copyBuffer, kCFAllocatorDefault , kCFAllocatorDefault, 0, &receivedAudioBufferList);
if (status != noErr) {
  NSLog(@"Error in CMSampleBufferSetDataBufferFromAudioBufferList");
  CFRelease(blockBuffer);
  return;
}

代码级支持答案:

此代码看起来不错(尽管您需要添加一些额外的错误检查).我已经在一个实现AVCaptureAudioDataOutput委托captureOutput:didOutputSampleBuffer:fromConnection:方法的应用程序中成功测试了它, 以捕获和记录音频.我使用这个深拷贝代码时获得的音频看起来与我直接使用提供的样本缓冲区(没有深拷贝)时得到的相同.

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