Recherche avancée

Sur d’autres sites (5333)

• 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();
  
  
  
  }

• Learning Shell - creating a script with parameters that runs two separate cli apps

  16 mai 2013, par GuilhermeNagatomo

  I want to learn shell script, so I'm trying to download a youtube video using youtube-dl then convert it to mp3 using ffmpeg.

  I do it manually running youtube-dl http://youtube.com/watch?v=...
  then
  ffmpeg -i downloadedFile -ab 256000 -ar 44100 audioFile.mp3.

  I know that I need to pass two arguments to my script, one for the video url and another for the audio file to keep things as simple as possible, but I don't know how to start. Maybe grep the video id in the url and using it to know which file to use to convert into mp3 ? (since youtube-dl saves the video named by it's id)

  Can someone recommend me an article or documentation that can help me ?

• FFMPEG - Speed up video for time lapse - quicker/faster ?

  15 juillet 2023, par Chad Baldwin

  Okay, I know this question has been asked a bajillion times. However, I have one small addition to the question that I haven't seem to have been able to find in my googling.

  



  I'm certainly not a pro at FFMPEG...I've been using the standard speed up/slow down template for FFMPEG, the one I'm using is :

  



  ffmpeg -i input.mp4 -filter:v "setpts=PTS/60" -an output.mp4


  



  I'm currently working with an hour long 4K/60FPS video...I want to shrink it down to about 30 seconds or so, so I'm using PTS/100, and I don't need audio...the problem is, this is taking FOREVER...which I completely expected it to.

  



  But as I'm sitting here waiting for it to finish...I can't help but wonder...is there a faster/more efficient way to accomplish this ? I know there's a lot of weird things about FFMPEG in regards to the order of the commands you use to speed up seek time, and presets and etc.