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• Applying gamma via ffmpeg does not match result in nuke/fusion/resolve

  17 mai 2022, par Kiwi

  I'm trying to convert a exr stack in linear colorspace to an H.264 .mov file in rec709 colorspace using ffmpeg. I am expecting it to match the result I get from Nuke, Fusion or Resolve.

  


  In an editor, I can apply 2.4 gamma and export an H.264 .mov file. But when I try applying 2.4 gamma via ffmpeg, it does not match. It seems less saturated from ffmpeg.

  


  Here is the command I'm using :

  


  ffmpeg -y -gamma 2.4 -i C:/input/file_%04d.exr -vcodec libx264 -pix_fmt yuv420p -preset slow -crf 17 -r 25 C:/output.mov


  


• No such file of directory Windows 10 PowerShell

  7 avril 2020, par Constadinos Chatzis

  Till now the command i use to convert HDR videos to SDR worked just fine till now. I am gettong always the error message "F:\_4k_Movies_\Dolittle: no such file or directory" any idea what's whong ?

  



  .\ffmpeg.exe -i F:\_4k_Movies_\Dolittle 4K.mkv -vf zscale=t=linear:npl=100,format=gbrpf32le,
zscale=p=bt709,tonemap=tonemap=hable:desat=0,zscale=t=bt709:m=bt709:r=tv,
format=yuv420p -c:v libx265 -crf 10 -preset fast F:\_4k_Movies_\Dolittle.SDR.mkv


  


• How to put QUdp packets into AVPacket/FFmpeg

  11 juin 2014, par user2772673

  I want to write a application that had to receive udp packets by QT UdpSocket, packets consists metadata and video.

  Video data is the same as from ffmpeg udp stream.

  I divided this packets and selected video data, now I want to put this video data into AVpacket, decode it and display in window.

  So I have Qbytearray from udp socket and don’t know how to convert it to AVpacket.
  (when I write this Qbytearray to file I have proper video file so data is good)

  procFrame is called every time I get a UDP packet. In constructor I have codec initialization and other init stuff.
  Cdatagrams contains one frame of video ( key frame or differential frame). Codec is mpeg2

      void myThread::procFrame()
  
      {
  
          findex++;
  
          if(av_read_frame(pFormatCtx,&packet)<0)///now pFormatCtx pointing to file on disk
  
              qDebug()<<"avreadframe failed";
  
  
  
          Spacket.data = new uint8_t[Cdatagrams.size()];///Spacket is empty packet that I want to fill by Qbytearray Cdatagrams 
  
  
  
          memcpy(Spacket.data,Cdatagrams.data_ptr(),Cdatagrams.size());////here is the problem
  
  
  
          int framecount;
  
          int frameFinished;
  
  
  
          avcodec_decode_video2(pCodecCtx,pFrame,&frameFinished,&Spacket);
  
              qDebug()<<  "framefinished " </ Write pixel data
  
              for(y=0; ydata[0]+y*pFramew->linesize[0], width*3);
  
  
  
              emit frameReady(img);
  
          }
  
  
  
      }

  In this version I have frameFinished==0 so Spacket isn’t properly prepared