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• ffmpeg decode one video frame at a time

  28 juillet 2014, par Krishna

  Most ffmpeg examples online show video decoding using a while () and the entire sequence is decoded in one attempt. For example,

  while(av_read_frame(pFormatCtx, &packet)>=0) {
  
      if(packet.stream_index==videoStream) {
  
  
  
          // Decode video frame
  
          avcodec_decode_video(pCodecCtx, pFrame, &frameFinished,
  
                       packet.data, packet.size);
  
  
  
          // Did we get a video frame?
  
          if(frameFinished) {
  
               ... do something   
  
          }
  
       } 
  
  
  
    // Free the packet that was allocated by av_read_frame
  
    av_free_packet(&packet);
  
  }

  Is there a technique to (1) create a function that will decode only one frame and (2) then call that function repeatedly (how many ever times needed).

  I wrote such a function and tried to decode an HEVC stream and I always get this error "Could not find ref with POC xx", where xx stands for some integer. Looks like it can’t find references — how do I get around this ?

  Thanks !

• Python Youtube-dl convert to mp4

  27 mars 2021, par Church.exe

  (if it matters, I'm on windows)

  


  So I am trying to download a Youtube video in an Mp4 format (the program I am putting it into has limited compatibility) with audio but whatever I find online either doesn't work how people are saying it does (leading me to believe it is either outdated, missing context, or for a different OS) or is formatted in a way that doesn't make sense.

  


  My current code is :

  


  if PreferredOutput == 1:
    with youtube_dl.YoutubeDL({'format' : 'bestvideo+bestaudio[ext=m4a]/bestvideo+bestaudio/best', 'merge-output-format' : 'mp4'}) as ydl:
        ydl.download([url])


  


  but when I test it, it just seems to output the file as normal.(which I am guessing is the format the video file was uploaded to youtube as though I could be mistaken) What should I do/am I missing to make this only output (final) Mp4s ? (after the fact ffmpeg conversion or something similar is fine for my purposes)

  


• How do I configure ffmpeg to enable rtpdec.h or rtpdec_h264

  3 mai 2022, par mike

  I'd like to build ffmpeg libraries so I can use the functionality in rtpdec_h264.c.

  


  As far as I can tell, my current build is not including this, at least not in the headers. I can happily encode and decode h264 via AVFormat structs, but now I'm trying to decode rtp packets directly.

  


  I might be missing something but it seems like I might just need to turn on another option when building ffmpeg - if so, what is that option ?

  


  I can see rtpdec is listed in the configure script as part of CONFIG_EXTRA - it looks to me like that should be building by default, but again no sign of the functions when I dump the contents of the libavformat .lib or .dll (I'm on Windows).

  


  Should I expect rtpdec.h to be in the include/libavformat output ?

  


  Or - am I missing something and the rtpdec stuff is handled internally, and I should be going through some other interface ?

  


  Current configure string is ./configure --prefix=./../../build/ffmpeg --enable-nonfree --enable-gpl --enable-shared --enable-cuda-nvcc --enable-libx264 --enable-libx265 --enable-libnpp --extra-cflags="-I../../build/x264/include -I../x265_git/source -I../nv_sdk -I../build/nv-codec-headers/include/ffnvcodec" --extra-ldflags="-L../../build/x264/lib -L../nv_sdk -L../x265_git/build/vc16-x86_64/Release"