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• Inaccurate sleep using C++11 on Windows

  15 février 2017, par Ashe the human

  I’ve been using C++11 sleep to give the interval between video frames. This method I’ve been using makes playback elongated on Windows.

  #include <iostream>
  
  #include <thread>
  
  #include <sstream>
  
  
  
  
  
  int main(const int argc, const char **args)
  
  {
  
      std::stringstream sb;
  
  
  
      if(argc &lt; 2)
  
          return 1;
  
      int fps = 0;
  
      sb &lt;&lt; args[1];
  
      sb >> fps;
  
  
  
      if(fps &lt;= 0)
  
          return 1;
  
      int i;
  
  
  
  
  
      while(true)
  
      {
  
          std::chrono::high_resolution_clock::time_point start, end;
  
  
  
          start = std::chrono::high_resolution_clock::now();
  
          for(i=0; i fps));
  
          }
  
          end = std::chrono::high_resolution_clock::now();
  
  
  
          auto c = std::chrono::duration_cast(end - start).count();
  
          std::cerr &lt;&lt; c &lt;&lt; std::endl;
  
      }
  
  
  
      return 0;
  
  }
  
  </sstream></thread></iostream>

  Running that program with 60 gives about 1004 1006 on Linux and 1065 1075 on Windows. So, I’m guessing, after playing a 2-hour long video, more than a minute is passed than just 2 hours.

  timeBeginPeriod() has no effect. Is using timer(like this one ?) is the only way to implement media players on Windows ? What about on Linux ? I think it’s the right way considering the fact that ffplay uses av_usleep().

  So sad that there’s no portable way.

• How can I capture video from different windows using ffmpeg ?

  13 janvier 2016, par RdB

  I have a proprietary IPTV player, and my goal is to capture a video from this player’s several windows simultaneously. I’m able to do that with ffmpeg and VLC (for instance) using vlc windows’ titles like this :

  ffmpeg -f gdigrab -framerate 30 -i title="german.avi - VLC media player" -b:v 3M  germ.flv
  
  
  
  
  
  ffmpeg -f gdigrab -framerate 30 -i title="2015-05-10 Sportscene.mkv - VLC media player" -b:v 3M  scot.flv

  and so on.

  But when I run 2 or more instances of that proprietary player, all of its windows’ titles are similar. So the question is how can I specify which window’s video in which file to record ?

• ffmpeg : wmv files generated on Mac can't be played in Windows

  16 juin 2015, par TTZ

  On Mac OS X 10.6.8, I converted a animated gif to a video file in wmv (a requested file format) by using

  ffmpeg -i File.gif -s 400x400 NewFile.wmv

  The video file played fine using VLC on Mac.
  The file can’t be played on a Windows 7 machine using the Windows Media Player. Is there a way that I can save the animated gif as a WMV file that can be played using the Windows Media Player on a Windows 7 machine ?

  Many thanks for your time !