Recherche avancée

Sur d’autres sites (12228)

• FFmpeg - generate x264 CBR video transport stream with C-API

  6 juillet 2020, par ZeroDefect

  Using various posts sprinkled around the Internet, including this one here on SO, I've been able to understand how to use the FFmpeg cli to generate a CBR video bitrate using the x264 codec (wrapped in an MPEG-2 transport stream). Note : I'm concerned with the video bitrate - nothing else.

  


  ffmpeg -i cbr_test_file_input.mp4 -c:v libx264 -pix_fmt yuv420p -b:v 6000000 -preset fast -tune film -g 25 -x264-params vbv-maxrate=6000:vbv-bufsize=6000:force-cfr=1:nal-hrd=cbr -flags +ildct+ilme x264_cbr_test_output.ts


  


  However, I'm trying to approach this from an FFmpeg C-API point of view. I'm having issues. I've knocked together some code to try do something very similar to what is being done in the FFmpeg CLI. I can generate a transport stream of what I think should be CBR, but the profile of the video bitrate is very different from what I thought was the FFmpeg cli equivalent :

  


  The initialisation of the AVCodecContext looks something like :

  


        av_dict_set(&amp;pDict, "preset", "faster", 0);&#xA;      av_dict_set(&amp;pDict, "tune", "film", 0);&#xA;      av_dict_set_int(&amp;pDict, "rc-lookahead", 25, 0);&#xA;&#xA;      pCdcCtxOut->width = pCdcCtxIn->width;&#xA;      pCdcCtxOut->height = pCdcCtxIn->height;&#xA;      pCdcCtxOut->pix_fmt = AV_PIX_FMT_YUV420P;&#xA;      pCdcCtxOut->gop_size = 25;&#xA;&#xA;      // Going for 6Mbit/s&#xA;      pCdcCtxOut->bit_rate = 6000000;&#xA;      //pCdcCtxOut->rc_min_rate = pCdcCtxOut->bit_rate;&#xA;      pCdcCtxOut->rc_max_rate = pCdcCtxOut->bit_rate;&#xA;      pCdcCtxOut->rc_buffer_size = pCdcCtxOut->bit_rate;&#xA;      pCdcCtxOut->rc_initial_buffer_occupancy = static_cast<int>((pCdcCtxOut->bit_rate * 9) / 10);&#xA;&#xA;      std::string strParams = "vbv-maxrate="&#xA;                              &#x2B; std::to_string(pCdcCtxOut->bit_rate / 1000)&#xA;                              &#x2B; ":vbv-bufsize="&#xA;                              &#x2B; std::to_string(pCdcCtxOut->bit_rate / 1000)&#xA;                              &#x2B; ":force-cfr=1:nal-hrd=cbr";&#xA;&#xA;      av_dict_set(&amp;pDict, "x264-params", strParams.c_str(), 0);&#xA;&#xA;      pCdcCtxOut->field_order = AV_FIELD_TT;&#xA;      pCdcCtxOut->flags = (AV_CODEC_FLAG_INTERLACED_DCT | AV_CODEC_FLAG_INTERLACED_ME | AV_CODEC_FLAG_CLOSED_GOP);&#xA;&#xA;      // WARN: Make some assumptions here!&#xA;      pCdcCtxOut->time_base = AVRational{1,25};&#xA;      pCdcCtxOut->framerate = AVRational{25,1};&#xA;      pCdcCtxOut->sample_aspect_ratio = AVRational{64,45};&#xA;</int>

  


  The output graphs appear very different :

  


  

  


  Above is the FFmpeg CLI output - video bitrate holds fairly steady.

  


  

  


  Above is the output of my sample application - some significant dips in the video bitrate.

  


  I've taken this a step further and created a git repo consisting of :

  


  

  • Code of sample application

  


  • Test input file (.mp4)

  


  • Outputs (.ts file) of tests

  


  • Graphs of output bitrates.

  


  


• FFmpeg subtitle filter set start time

  31 décembre 2020, par CasualDemon

  I am trying to burn-in subtitles for a shorter section of a video, but using the subtitles filter always starts from the beginning of the subtitle stream, not at the specified start time, even when copying from the same video.

  


  So for example if I start an encode 10 minutes in to a film, the video will properly be set from there, but the subtitles will start from the beginning (10 minute offset in this case).

  


  ffmpeg -y -ss 600.0 -to 660.0 -i movie.mkv -filter_complex "[0:0]subtitles='movie.mkv':si=1[v]" -map "[v]" -c:v libx265 -crf 22 output.mkv


  


  This is not a problem when using picture based subtitles and the overlay filter, such as :

  


  -filter_complex "[0:0][0:2]overlay[v]"


  


  It seems to only affect text based subtitles. I don't know if this is just not possible and will require another solution, or if I am approaching it wrong. Any help is appreciated !

  


• FFMpeg + Beanstalk : How to pass the processes to it

  14 juillet 2012, par Ilia Rostovtsev

  I'm working around on the video web site ! I have a simple PHP function that is used to start complicated conversion processes. The problem is that FFMpeg and Mencoder are extremely resourceful and having one process of it is something that makes httpd slow down but multiple processes just hang it completely. I want to my conversion processes with Beanstalk (or anything else). Everything is working well right now : converting, logging and etc.

  My concrete question is : How to transfer my current jobs to Beanstalk ?

  I have very simple PHP code :

  RunInBackground('convert.php', array($initial_file_name, $vid), $LogFilePath);

  And the function looks also quite clear :

  function RunInBackground($sPHPFile, $aParam = array(), $sLogFile = '')
  
  {
  
      global $config;
  
  
  
      $sCmd = $config['phppath'] . ' ' . $config['BASE_DIR'] . '/' . $sPHPFile;
  
      foreach ($aParam as $s)
  
      {
  
          $sCmd .= ' ' . $s;
  
      }
  
  
  
  
  
          $sCmd .= ' > ' . ($sLogFile != '' ? $config['BASE_DIR'] . '/' . $sLogFile : '/dev/null');
  
  
  
          if ( iBgProc($sCmd) )
  
          {
  
              return true;
  
          }
  
          else
  
          {
  
              return false;
  
          }
  
  
  
  }
  
  
  
  function iBgProc($sCmd, $iPrio = 0)
  
  {
  
      if ($iPrio)
  
      {
  
          $iPID = shell_exec("nohup nice -n $iPrio $sCmd 2> /dev/null & echo $!");
  
      }
  
      else
  
      {
  
          $iPID = shell_exec("nohup $sCmd 2> /dev/null & echo $!");
  
      }
  
  
  
      return($iPID);
  
  }

  Now what would Beanstalk correct code would look like so these processes would NOT start all at the same time if multiple videos are uploaded ?

  If you believe that for my needs is better to use something else but Beanstalk and you know how to implement it, I would be still happy to see it !

  Thanks !