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• Streaming to YouTube from DJI-SDK

  6 avril 2017, par d0n13

  I’m trying to figure out how to take the camera frames in the DJI-SDK and push them to some form of encode so that I can create a live stream for YouTube.

  Has anybody got this working ? I understand most people use FFmpeg for streaming but my understanding is basic enough on how that project works.

  I’d love if somebody could share some resources on how we could go about getting this to work. I’ve seen the question on the web but I’ve found nothing that comes close to getting a solution for this.

  I need it for a project and there is a commercial solution available but it’s expensive and I can’t afford it and I’d be happy enough to code this if I can understand how to go about it and maybe get some help.

  I’d be happy enough to make an open source version of this is anyone can help.

  Thanks guys, hope we can make this...
  Donie

• Seeking to video frame of h264 codec in mp4 container with FFmpeg. Packet pts is always 0

  28 avril 2015, par Maxito

  I’m trying to seek to the nearest keyframe of a specific frame with FFmpeg but whenever I obtain the next frame with av_read_frame after seeking, the packet pts or dts are always 0. This only happens with h264/mp4 videos as it works correctly for some codecs in .avi container.

  I have tried using avformat_seek_file and av_seek_frame but they give me the same result.

  I also read that I shouldn’t be reading timestamps from the packet, so I tried decoding the packet first with avcodec_decode_video2 and reading AVFrame->pts information but this value is always invalid for h264/mp4 videos.

  This is the relevant code of what I’m trying to do :

  /*Relevant from header*/
  
  AVCodecContext pCodecCtx;
  
  AVFormatContext *pFormatCtx;
  
  int videoStreamIndex;
  
  
  
  int Class::getFrame(int desiredFrame, bool seek)
  
  if(seek)
  
  {
  
      /* We seek to the selected frame */
  
      if(avformat_seek_file(pFormatCtx, videoStreamIndex, 0, desiredFrame, desiredFrame, AVSEEK_FLAG_BACKWARD) < 0)
  
      //if(av_seek_frame(pFormatCtx, mVideoStream, desiredFrame, AVSEEK_FLAG_BACKWARD) < 0)
  
      {
  
      // error management
  
      }
  
      avcodec_flush_buffers(pCodecCtx);
  
  }
  
  
  
  AVPacket packet;
  
  int frameFinished;
  
  /* Loop until we find the next video frame */
  
  while(av_read_frame(pFormatCtx, &packet) >= 0 )
  
  {
  
      if(packet.stream_index == videoStreamIndex)
  
      {
  
          avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
  
          int pcktPts;
  
  
  
          /*** management of other codecs here using av_frame_get_best_effort_timestamp() ***/
  
  
  
  
  
          /* With this approach I have been getting correct pts info after many av_read_frame loops */
  
          if(pCodecCtx->codec->id == AV_CODEC_ID_H264 && videoPath.toLower().endsWith(".mp4"))
  
          {
  
              pcktPts = av_rescale_q(packet.pts, //pFrame->pts always invalid here
  
                                        pFormatCtx->streams[videoStreamIndex]->time_base,
  
                                        pFormatCtx->streams[videoStreamIndex]->codec->time_base);
  
              pcktPts = (pcktPts/pCodecCtx->ticks_per_frame);
  
          }
  
  
  
          if(pcktPts == desiredFrame) ....
  
          /* more irrelevant code for reading, converting frame, etc */

  Perhaps I’m dealing with this kind of codec incorrectly, any idea will be highly appreciated.

  As a note, I am only interested in video frames.

• Clang cannot find dependency of a shared library

  27 juillet 2021, par zana zakaryaie nejad

  I have a project with two submodules (say A and B). A depends on FFmpeg and B depends on A. Clang successfully finds FFmpeg and builds libA.so but it fails to build libB.so because it can't find FFmpeg ! The strange thing is that GCC can handle this. When I move find_package(FFmpeg) from submodule A's CMakelists to the project's CMakelist, then libB.so is successfully built. But this is an ugly solution. Any suggestion for the reason behind this strange behaviour ?