AVCapture appendSampleBuffer

Question

我已经找遍了所有地方，尝试了我能想到的任何东西，我都快疯了。

我制作了一个iPhone应用程序，它使用AVFoundation -特别是AVCapture来使用iPhone摄像头捕获视频。

我需要有一个自定义的图像，是覆盖在录像中包括视频馈送。

到目前为止，我已经设置了AVCapture会话，可以显示提要，访问帧，将其另存为UIImage，并将覆盖图像添加到它上。然后将这个新的UIImage转换为CVPixelBufferRef。为了再次检查bufferRef是否正常工作，我将其转换为UIImage，它仍然可以很好地显示图像。

当我尝试将CVPixelBufferRef转换为CMSampleBufferRef以附加到AVCaptureSessions assetWriterInput时，问题就开始了。当我尝试创建CMSampleBufferRef时，它总是返回NULL。

下面是-(空)captureOutput函数

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

 UIImage *botImage = [self imageFromSampleBuffer:sampleBuffer];
 UIImage *wheel = [self imageFromView:wheelView];

 UIImage *finalImage = [self overlaidImage:botImage :wheel];
 //[previewImage setImage:finalImage]; <- works -- the image is being merged into one UIImage

 CVPixelBufferRef pixelBuffer = NULL;
 CGImageRef cgImage = CGImageCreateCopy(finalImage.CGImage);
 CFDataRef image = CGDataProviderCopyData(CGImageGetDataProvider(cgImage));
 int status = CVPixelBufferCreateWithBytes(NULL,
             self.view.bounds.size.width,
             self.view.bounds.size.height,
             kCVPixelFormatType_32BGRA, 
             (void*)CFDataGetBytePtr(image), 
             CGImageGetBytesPerRow(cgImage), 
             NULL, 
             0,
             NULL, 
             &pixelBuffer);
 if(status == 0){
  OSStatus result = 0;

  CMVideoFormatDescriptionRef videoInfo = NULL;
  result = CMVideoFormatDescriptionCreateForImageBuffer(NULL, pixelBuffer, &videoInfo);
  NSParameterAssert(result == 0 && videoInfo != NULL);

  CMSampleBufferRef myBuffer = NULL;
  result = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault,
            pixelBuffer, true, NULL, NULL, videoInfo, NULL, &myBuffer);
  NSParameterAssert(result == 0 && myBuffer != NULL);//always null :S

  NSLog(@"Trying to append");

  if (!CMSampleBufferDataIsReady(myBuffer)){
   NSLog(@"sampleBuffer data is not ready");
   return;
  }

  if (![assetWriterInput isReadyForMoreMediaData]){
   NSLog(@"Not ready for data :(");
   return;
  }

  if (![assetWriterInput appendSampleBuffer:myBuffer]){   
   NSLog(@"Failed to append pixel buffer");
  }



 }

}

我经常听到的另一个解决方案是使用AVAssetWriterInputPixelBufferAdaptor，它消除了进行混乱的CMSampleBufferRef包装的需要。然而，我已经搜索了堆栈和苹果开发人员论坛和文档，没有找到关于如何设置或如何使用它的明确描述或示例。如果任何人有它的一个工作的例子，你可以告诉我或帮助我解决上述问题-已经不间断地工作了一个星期，我在wits结束。

如果你需要任何其他信息，请告诉我

提前谢谢你，

迈克尔

Answer 1

你需要AVAssetWriterInputPixelBufferAdaptor，下面是创建它的代码：

    // Create dictionary for pixel buffer adaptor
NSDictionary *bufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA], kCVPixelBufferPixelFormatTypeKey, nil];

// Create pixel buffer adaptor
m_pixelsBufferAdaptor = [[AVAssetWriterInputPixelBufferAdaptor alloc] initWithAssetWriterInput:assetWriterInput sourcePixelBufferAttributes:bufferAttributes];

以及使用它的代码：

// If ready to have more media data
if (m_pixelsBufferAdaptor.assetWriterInput.readyForMoreMediaData) {
    // Create a pixel buffer
    CVPixelBufferRef pixelsBuffer = NULL;
    CVPixelBufferPoolCreatePixelBuffer(NULL, m_pixelsBufferAdaptor.pixelBufferPool, &pixelsBuffer);

    // Lock pixel buffer address
    CVPixelBufferLockBaseAddress(pixelsBuffer, 0);

    // Create your function to set your pixels data in the buffer (in your case, fill with your finalImage data)
    [self yourFunctionToPutDataInPixelBuffer:CVPixelBufferGetBaseAddress(pixelsBuffer)];

    // Unlock pixel buffer address
    CVPixelBufferUnlockBaseAddress(pixelsBuffer, 0);

    // Append pixel buffer (calculate currentFrameTime with your needing, the most simplest way is to have a frame time starting at 0 and increment each time you write a frame with the time of a frame (inverse of your framerate))
    [m_pixelsBufferAdaptor appendPixelBuffer:pixelsBuffer withPresentationTime:currentFrameTime];

    // Release pixel buffer
    CVPixelBufferRelease(pixelsBuffer);
}

别忘了释放你的pixelsBufferAdaptor。

Answer 2

我是通过使用CMSampleBufferCreateForImageBuffer()来实现的。

OSStatus ret = 0;
CMSampleBufferRef sample = NULL;
CMVideoFormatDescriptionRef videoInfo = NULL;
CMSampleTimingInfo timingInfo = kCMTimingInfoInvalid;
timingInfo.presentationTimeStamp = pts;
timingInfo.duration = duration;

ret = CMVideoFormatDescriptionCreateForImageBuffer(NULL, pixel, &videoInfo);
if (ret != 0) {
    NSLog(@"CMVideoFormatDescriptionCreateForImageBuffer failed! %d", (int)ret);
    goto done;
}
ret = CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault, pixel, true, NULL, NULL,
                                         videoInfo, &timingInfo, &sample);
if (ret != 0) {
    NSLog(@"CMSampleBufferCreateForImageBuffer failed! %d", (int)ret);
    goto done;
}