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• Syncing decoded video using Ffmpeg

  30 juin 2012, par Infiniti Fizz

  I am using Ffmpeg to decode and play video files. I have currently got the video playing and the audio playing at as fast as the CPU can decode and display them. The problem is that I want to play the video and audio in sync using the system clock.

  I've searched around for some help but can't find anything substantial other than dranger's tutorial 05 but I don't really understand what he is doing because my program isn't written in the same way as his.

  I am using mjpeg files and so the pts seems to be retrieved every single time a frame is decoded, I have multiplied the pts by the time_base as dranger does to get the value in seconds but the resolution seems to be only seconds and so I get the value "6" 25 times and then "7" 25 times as the video runs at 25 frames per second.

  Is there not a more accurate value ? Or way to get a more accurate value and if so, how would I go about syncing to this value ? I am using SDL to display the value so can I just use a SDL_Delay() of the value I get ?

  Thanks for your time,

  Infinitifizz

• Getting accurate time from FFMPeg with Objective C (Audio Queue Services)

  2 avril 2012, par Winston

  My iPhone app plays an audio file using FFMPeg.

  I'm getting the elapsed time (to show to user) from the playing audio (in minutes and seconds after converting from microseconds, given by FFMPeg) like so :

  AudioTimeStamp currentTimeStamp;
  
  AudioQueueGetCurrentTime (audioQueue, NULL, &currentTimeStamp, NULL);
  
  
  
  getFFMPEGtime = currentTimeStamp.mSampleTime/self.basicAudioDescription.mSampleRate;
  
  
  
  self.currentAudioTime = [NSString stringWithFormat: @"%02d:%02d",
  
                              (int) getFFMPEGtime / (int)60000000,
  
                              (int) ((getFFMPEGtime % 60000000)/1000000)];

  Everything works fine, but when I scrub back or forward to play another portion of the song, the elapsed time will go back to zero, no matter the current position. The timer will always zero out.

  I know I'm suposed to do some math to keep track of the old time and the new time, maybe constructing another clock or so, perhaps implementing another callback function, etc... I'm not sure what way I should go.

  My questions are :

  1) What's the best approach to keep track of the elapsed time when going back/forward in a song, avoiding the clock to always going back to zero ?

  2) Should I look deeply into FFMPeg functions or should I stick with Objective-C and Cocoa Touch for solving this problem ?

  Please, I need some advices/ideas from experienced programmers. I'm stuck. Thanks beforehand !

• Merge remote-tracking branch ’cus/stable’

  10 juillet 2013, par Michael Niedermayer

  Merge remote-tracking branch ’cus/stable’
  * cus/stable :
  
    ffplay : assume 0 stream start time if start time is unset in duration check
  
    ffplay : do not update audio clock with old audio pts if current frame is AV_NOPTS_VALUE
  Merged-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] ffplay.c