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• FFmpeg resize without upscaling

  9 novembre 2016, par Alan

  I am working on a script that searches for all media files in the current directory and subdirectories and then batch encodes them to H.265. I was hoping to put in some max frame sizes to make things that are 1080p to be 720p. That is the straightforward part but I have some that are 480p and I don’t want those to end up as 720p. How can I modify my ffmpeg filters to take that into account ?

  The command :

  ffmpeg -i input -c:v hevc_nvenc -preset medium -crf 28 -c:a copy output.mp4

• Read from UDP Multicast RTSP Video Stream

  24 avril 2012, par hatboyzero

  I am currently developing an application that needs to decode a UDP multicast RTSP stream. At the moment, I can view the RTP stream using ffplay via

  ffplay -rtsp_transport udp_multicast rtsp://streamURLGoesHere

  However, I am trying to use FFMPEG to open the UDP stream via (error checking and cleanup code removed for the sake of brevity).

  AVFormatContext* ctxt = NULL;
  
  av_open_input_file(
  
      &ctxt,
  
      urlString,
  
      NULL,
  
      0,
  
      NULL
  
  );
  
  
  
  av_find_stream_info(ctxt);
  
  
  
  AVCodecContext* codecCtxt;
  
  
  
  int videoStreamIdx = -1;
  
  for (int i = 0; i < ctxt->nb_streams; i++)
  
  {
  
      if (ctxt->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
  
      {
  
          videoStreamIdx = i;
  
          break;
  
      }
  
  }
  
  
  
  AVCodecContext* codecCtxt = ctxt->streams[videoStreamIdx]->codec;
  
  AVCodec* codec = avcodec_fine_decoder(codecCtxt->codec_id);
  
  avcodec_open(codecCtxt, codec);
  
  
  
  AVPacket packet;
  
  while(av_read_frame(ctxt, &packet) >= 0)
  
  {
  
      if (packet.stream_index == videoStreamIdx)
  
      {
  
          /// Decoding performed here
  
          ...
  
      }
  
  }
  
  
  
  ...

  This approach works fine with file inputs that consist of a raw encoded video stream, but for UDP multicast RTSP streams, it fails any error checking performed on av_open_input_file(). Please advise...

• FFmpeg capture, mkvtimestamp_v2 and timecode don't play nice

  24 mai 2021, par Bouke

  Trying to capture and modify the TC in-file afterwards.
I've found a nice way to store the timestamps from the capture.
Gyan's brillant filterchain

  


  This works fine using this line :

  


  ffmpeg -hide_banner -f "decklink" -queue_size "1073741824" -raw_format "auto" -format_code "Hi50" -video_input "sdi" -i "bm mini One" -filter_complex "settb=1/1000,setpts=RTCTIME/1000-1500000000000,mpdecimate,split[out][ts];[out]setpts=N/25/TB[out]" -map "[out]" -c:a "copy" -c:v "prores" -profile:v "1" -vendor "ap10" -pix_fmt "yuv422p10le" "/Volumes/Data/tst1.mov" -map "[ts]" -f mkvtimestamp_v2 "/Volumes/Data/time.txt" -vsync 0


  


  But, when I add -timecode "00:00:00:00" (to force a TC atom in the output), horrible things happen.

  


  ffmpeg -f "decklink" -queue_size "1073741824" -raw_format "auto" -format_code "Hi50" -video_input "sdi" -i "bm mini One" -filter_complex "settb=1/1000,setpts=RTCTIME/1000-1500000000000,mpdecimate,split[out][ts];[out]setpts=N/25/TB[out]" -map "[out]" -timecode "00:01:00:00" -c:a "copy" -c:v "prores" -profile:v "1" -vendor "ap10" -pix_fmt "yuv422p10le" "/Volumes/Data/tst1.mov" -map "[ts]" -f mkvtimestamp_v2 "/Volumes/Data/time.txt" -vsync 0


  


  The timecode does not run at the video speed, skips a frame or two here and there, and the image freezes after a random amount of time (between 10 seconds and a minute or so).

  


  How come the timecode can mess up stuff that much ? From what I understand it's just a couple of atoms in the moov atom, and a reference where the actual TC value (as frames) is stored in the mdat.

  


  I highly suspect the -vsync 0 to also work on the video, and I've had issues with that before. If I omit that, the video is fine, the TC is fine, but there is no metadata output, just the # timecode format v2