Encoding raw YUV420P to h264 with AVCodec on iOS

问题:

I am trying to encode a single YUV420P image gathered from a CMSampleBuffer to an AVPacket so that I can send h264 video over the network with RTMP.

The posted code example seems to work as avcodec_encode_video2 returns 0 (Success) however got_output is also 0 (AVPacket is empty).

Does anyone have any experience with encoding video on iOS devices that might know what I am doing wrong?

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

  // sampleBuffer now contains an individual frame of raw video frames
  CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

  CVPixelBufferLockBaseAddress(pixelBuffer, 0);

  // access the data
  int width = CVPixelBufferGetWidth(pixelBuffer);
  int height = CVPixelBufferGetHeight(pixelBuffer);
  int bytesPerRow = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
  unsigned char *rawPixelBase = (unsigned char *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);


  // Convert the raw pixel base to h.264 format
  AVCodec *codec = 0;
  AVCodecContext *context = 0;
  AVFrame *frame = 0;
  AVPacket packet;

  //avcodec_init();
  avcodec_register_all();
  codec = avcodec_find_encoder(AV_CODEC_ID_H264);

  if (codec == 0) {
    NSLog(@"Codec not found!!");
    return;
  }

  context = avcodec_alloc_context3(codec);

  if (!context) {
    NSLog(@"Context no bueno.");
    return;
  }

  // Bit rate
  context->bit_rate = 400000; // HARD CODE
  context->bit_rate_tolerance = 10;
  // Resolution
  context->width = width;
  context->height = height;
  // Frames Per Second
  context->time_base = (AVRational) {1,25};
  context->gop_size = 1;
  //context->max_b_frames = 1;
  context->pix_fmt = PIX_FMT_YUV420P;

  // Open the codec
  if (avcodec_open2(context, codec, 0) < 0) {
    NSLog(@"Unable to open codec");
    return;
  }


  // Create the frame
  frame = avcodec_alloc_frame();
  if (!frame) {
    NSLog(@"Unable to alloc frame");
    return;
  }
  frame->format = context->pix_fmt;
  frame->width = context->width;
  frame->height = context->height;


  avpicture_fill((AVPicture *) frame, rawPixelBase, context->pix_fmt, frame->width, frame->height);

  int got_output = 0;
  av_init_packet(&packet);
  avcodec_encode_video2(context, &packet, frame, &got_output)

  // Unlock the pixel data
  CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
  // Send the data over the network
  [self uploadData:[NSData dataWithBytes:packet.data length:packet.size] toRTMP:self.rtmp_OutVideoStream];
}

Note: It is known that this code has memory leaks because I am not freeing the memory that is dynamically allocated.

UPDATE

I updated my code to use @pogorskiy method. I only try to upload the frame if got output returns 1 and clear the buffer once I am done encoding video frames.