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• Blurry picture when decoding h264 mpegts udp stream with ffmpeg

  10 juin 2019, par Fredrik Axling

  Im using ffmpeg do read an udp stream (contains only video) and to decode frames , I then like to encode again , but during the decoding or from the demuxing i get blurry pictures pictures especially the lower part.

  I have a video player that also uses ffmpeg that displays the video perfectly and I try to look in that code but I don’t see any differences.
  In the log I se things like
  

  Invalid NAL unit 8, skipping.
  nal_unit_type : 1(Coded slice of a non-IDR picture), nal_ref_idc : 3
  
  Invalid NAL unit 7, skipping.
  
  bytestream overread td
  
  error while decoding MB 109 49, bytestream td
  

  The main things in the code looks like :

  av_register_all();
  
  
  
  AVFormatContext *fmt_ctx = 0;
  
  
  
  AVDictionary *options = 0;
  
  av_dict_set(&options, "analyzeduration", "500000", NULL);
  
  av_dict_set(&options, "probesize", "500000", NULL);
  
  char* url = "udp://239.0.0.3:8081";
  
  avformat_open_input(&fmt_ctx, url, 0, &options);
  
  
  
  avformat_find_stream_info(fmt_ctx, &options);
  
  
  
  int nRet = 0;
  
  av_dump_format(fmt_ctx, 0, url, 0);
  
  AVStream *pStream = fmt_ctx->streams[0];
  
  AVCodecID nCodecid = pStream->codec->codec_id;
  
  AVCodec* pCodec = avcodec_find_decoder(nCodecid);
  
  AVCodecContext* pCodecCtx = pStream->codec;
  
  
  
  nRet = avcodec_open2(pCodecCtx, pCodec, NULL);
  
  int nInH = pStream->codec->height;
  
  int nInW = pStream->codec->width;
  
  int nOutW = nInW / 4;
  
  int nOutH = nInH / 4;
  
  
  
  SwsContext* pSwsCtx = sws_getContext(nInW, nInH, AV_PIX_FMT_YUV420P,
  
                                       nOutW, nOutH, AV_PIX_FMT_RGB24,
  
                                       SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  
  
  m_pFilmWdg->m_img = QImage(nOutW, nOutH, QImage::Format_RGB888);
  
  int linesizes[4];
  
  av_image_fill_linesizes(linesizes, AV_PIX_FMT_RGB24, nOutW);
  
  
  
  
  
  for (;;)
  
  {
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;
  
      pkt.size = 0;
  
      nRet = av_read_frame(fmt_ctx, &pkt);
  
  
  
      nRet = avcodec_send_packet(pCodecCtx, &pkt);
  
  
  
      AVFrame*  picture = av_frame_alloc();
  
  
  
      nRet = avcodec_receive_frame(pCodecCtx, picture);
  
  
  
      if (AVERROR(EAGAIN) == nRet)
  
          continue;
  
  
  
      uint8_t* p[] = { m_pFilmWdg->m_img.bits() };
  
  
  
  
  
  
  
      nRet = sws_scale(pSwsCtx, picture->data, picture->linesize, 0, nInH, p, linesizes);
  
  
  
      av_packet_unref(&pkt);
  
      av_frame_free(&picture);
  
      m_pFilmWdg->update();
  
  
  
  }

• How to build and use ffmpeg libraries in Android project in Mac OS 10.9 ?

  28 septembre 2014, par Sunshinetpu

  In my Android project I have to create a video from some pictures. So I want to use FFmpeg libraries for it. I read many links about it (For example : http://www.roman10.net/how-to-build-ffmpeg-with-ndk-r9/comment-page-4/) I tried to build FFmpeg in my computer (MAC OS 10.9) but every advice didn’t work.
  Did anybody build and use FFmpeg in Adroid project (MAC OS) successfully ?
  Can anybody give me some advices ?
  Sorry for my English !

• How to use ffmpeg to encode multi-channel video ?

  13 juillet 2018, par Leo

  Like nomral video have RGB/YUV, 3 channels.
  Is it possible use the existing video convertor to encode more than 3 channel video ? (e.g. given 5 folders of the same number and resolution pictures, generate a 5-channel video from them)
  I not need to playback the 5-channel video, which is impossible for 3-channel display. I just need to encode it and then decode it back to images. Actually what I am looking for is not a playable video format, I am trying to compressing several similar video content into one file, so that hopefully they can share the motion vectors and save more space.

  Dose any existing video codec support this manipulation ? Or how should I rewrite some part of the exsiting video codec(some light weight implementation of H264) to support it ?