如何将图片编码为H264在Mac上使用AVFoundation,而不是使用x264

Question

我正在尝试使用FFmpeg而不是x264库将Mac广播客户端编码为H264.所以基本上,我能够从AVFoundation中获取原始帧CMSampleBufferRef或者AVPicture.那么有没有办法使用Apple框架将一系列图片编码成H264帧,比如AVVideoCodecH264.我知道编码它的方法使用AVAssetWriter,但是只将视频保存到文件中,但我不想要文件,相反,我想要AVPacket所以我可以使用FFmpeg发送.有谁有想法吗？谢谢.

Answer 1

在参考VideoCore项目之后,我可以使用Apple的VideoToolbox框架在硬件中进行编码.

1. 启动VTCompressionSession:

   // Create compression session
   err = VTCompressionSessionCreate(kCFAllocatorDefault,
                                frameW,
                                frameH,
                                kCMVideoCodecType_H264,
                                encoderSpecifications,
                                NULL,
                                NULL,
                                (VTCompressionOutputCallback)vtCallback,
                                self,
                                &compression_session);
   
   if(err == noErr) {
       comp_session = session;
   }
   

2. 将原始帧推送到VTCompressionSession

   // Delegate method from the AVCaptureVideoDataOutputSampleBufferDelegate
   - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
       // get pixelbuffer out from samplebuffer
       CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
       //set up all the info for the frame
       // call VT to encode frame
       VTCompressionSessionEncodeFrame(compression_session, pixelBuffer, pts, dur, NULL, NULL, NULL);
       }
   

3. 获取VTCallback中的编码帧,这是一个C方法,用作VTCompressionSessionCreate()的参数

   void vtCallback(void *outputCallbackRefCon,
           void *sourceFrameRefCon,
           OSStatus status,
           VTEncodeInfoFlags infoFlags,
           CMSampleBufferRef sampleBuffer ) {
       // Do whatever you want with the sampleBuffer
       CMBlockBufferRef blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer);
   
   }