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• Merge commit ’eae58428bd199f7d4670bf471f56ed204430878e’

  5 octobre 2015, par Hendrik Leppkes

  Merge commit ’eae58428bd199f7d4670bf471f56ed204430878e’
  * commit ’eae58428bd199f7d4670bf471f56ed204430878e’ :
  
    avcodec : Do not lock during open for codecs marked as having threadsafe init
  Merged-by : Hendrik Leppkes <h.leppkes@gmail.com>
  

• FFmpeg - avcodec_receive_frame doesn't receive all frames and lose frames before receving frames

  22 mars 2019, par Jinx

  The vcodec_receive_frame function didn’t receive the rest of the frames. I tested that there were totally 132 frames of the video and it only received 125 frames losing 7 frames at the END of the video. How can I get the lost frames back ?

  But something weird happened. As you can see the output from my MyDecode::receiveFrame() function. The code inside the block if (ret != 0){} executed first, but the lost frames are at the end of the video. So how could they come out first ? What caused this happen ?

  MyDecode.cpp

  AVFrame* MyDecode::receiveFrame()
  
  {
  
      mux.lock();
  
      if (!codecCtx) {
  
          mux.unlock();
  
          return 0;
  
      }
  
      AVFrame* frame = av_frame_alloc();
  
      int ret = avcodec_receive_frame(codecCtx, frame);
  
      mux.unlock();
  
      if (ret != 0)
  
      {
  
          static int lost_frames = 1;
  
          std::cout << "Lost frames: " << lost_frames << std::endl;
  
          lost_frames += 1;
  
          av_frame_free(&frame);
  
          return nullptr;
  
      }
  
      std::cout << "Received frames: " << received_frame_num << std::endl;
  
      received_frame_num += 1;
  
      return frame;
  
  }
  
  
  
  bool MyDecode::sendPacket(AVPacket* packet)
  
  {
  
      if (!packet || !packet->data || packet->size == 0)
  
          return false;
  
      mux.lock();
  
      if (!codecCtx) {
  
          mux.unlock();
  
          return false;
  
      }
  
      int ret = avcodec_send_packet(codecCtx, packet);
  
      mux.unlock();
  
      av_packet_free(&packet);
  
      if (ret != 0) {
  
          return false;
  
      }
  
      return true;
  
  }

  Console output

  Total frames: 132
  
  Lost frames: 1
  
  Lost frames: 2
  
  Lost frames: 3
  
  Lost frames: 4
  
  Lost frames: 5
  
  Lost frames: 6
  
  Lost frames: 7
  
  Received frames: 1
  
  Received frames: 2
  
  Received frames: 3
  
  ................
  
  Received frames: 125

  UPDATE :

  MyDemux.cpp

  AVPacket* MyDemux::readFrame()
  
  {
  
      mux.lock();
  
      if (!formatCtx) {
  
          std::cout << "formaetCtx is null" << std::endl;
  
          mux.unlock();
  
          return nullptr;
  
      }
  
      AVPacket* packet = av_packet_alloc();
  
      if (!packet) {
  
          std::cout << "packet is null" << std::endl;
  
          mux.unlock();
  
          return nullptr;
  
      }
  
  
  
      int ret = av_read_frame(formatCtx, packet);
  
      if (ret != 0) {
  
          while (true) {
  
              av_read_frame(formatCtx, nullptr);
  
          }
  
          mux.unlock();
  
          av_packet_free(&packet);
  
          av_packet_unref(packet);
  
          return nullptr;
  
      }
  
      media_type = packet->stream_index;
  
      mux.unlock();
  
      return packet;
  
  }

  main.cpp

  while (true) {
  
              AVPacket* pkt = demux.readFrame();
  
              if (demux.get_media_type() == 0) {
  
                  AVFrame* frame = video_decode.receiveFrame();
  
                  videoWidget->paintFrame(frame);
  
              }
  
              else if (demux.get_media_type() == 1) {
  
              }
  
              if (!pkt) {
  
                  std::cout << "to break" << std::endl;
  
                  break;
  
              }
  
          }

• Why are the colors transposed in my webm thumbnails ?

  9 décembre 2022, par Peter Chaplin

  I have been using ffmpeg to generate webm files from png frames, and the webm files run ok in my video player, but the thumbnail colours appear transposed - blue replacing red, purple replacing orange, brown replacing green. I've also encountered issue uploading the webm to an image hosting site (which normally does support webms), though this might be an issue on their end.
I'm on Ubuntu 22.04.1 LTS

  


  Does anyone know what might be causing this, and how to fix it ? Or how to check whether the webm files are ok or corrupted ?

  


  *Edit : ok, here's a side-by-side comparison of the thumbnails that appear in my file explorer - mp4 on the left and webm on the right.
Both were generated from the same set of pngs, using the same command except with the filename extension changed.

  


  

  


  Specifically,

  


  ffmpeg -framerate 24 -i Panel2Humanized/frame%04d.png panel2humanskin.webm


  


  and

  


  ffmpeg -framerate 24 -i Panel2Humanized/frame%04d.png panel2humanskin.mp4


  


  Both look the same when opened with a video player. It looks like the mp4 thumbnail grabbed the 1st frame while the webm grabbed the last, but the colors should be the same in each. (The text-bubble in the top-left is yellow in the mp4).

  


  *Follow-up : Apparently my WebMs are being generated in GBRP (Green-Blue-Red Planar) pixel format, the site I was trying to upload to requires YUV420P (Luma/Chroma 4:2:0 Planar) format, maybe that's the issue ? I'm still not sure exactly what that means or how to fix it.

  


  *Final follow-up : Looks like I needed to change the argument to :

  


  ffmpeg -framerate 24 -i Panel2Humanized/frame%04d.png -pix_fmt yuv420p paned2humanskin.webm