498560 - For video that need high system resource, adjust Tempo of video to match actual speed

Status: VERIFIED WORKSFORME

(Core :: Audio/Video, enhancement)

Description

[Biju]

Thanks to fix for Bug 494116, Bug 494120, Bug 466699, bug 470639
Now I am able to watch many Videos on my Celeron 1.20Hz PC

But I see for a big video the "Tempo" get changed.
ie, the media sized video at
http://www.double.co.nz/video_test/test4.html
will play little stretched, a one second part of video 
will complete only by 1.25 second.

Is it possible to increase Tempo automatically so that 
a 1 second part of movie play exactly 1 second long.


I have a JS to find actual skip.

(function(){
  var _ = window;
  _.videolist = document.getElementsByTagName('video');
  _.videocurr=0;
  if(_.videolist.length > 1){
    var msg = "There are " + _.videolist.length 
            + " videos, Choose 1, 2 ...";
    _.videocurr = (prompt(msg ,"") * 1 || 1) - 1;
  }
  _.video_scan || (_.video_scan = setInterval(showspeed,2000));
  _.videolasttime = new Date();
  _.videolastpos = 0;

  function showspeed(){
    var currtime = new Date();
    var currpos = _.videolist[_.videocurr].currentTime;
    var diffpos =  (currpos - _.videolastpos) * 1000;
    var difftime =  currtime - _.videolasttime;
    document.title  = "Tempo Ratio (expected = 1) : " 
                  + diffpos / difftime ;
    _.videolasttime = currtime ;
    _.videolastpos = currpos;    

  }
})();




Usage and Test Steps:-
1. get a PC with low performance, and latest trunk Firefox installed
2. install "shell" bookmarklet from 
   https://www.squarefree.com/bookmarklets/webdevel.html
3. go to a website with video
4. Launch "shell" bookmarklet 
5. run my JS "to find actual skip"
6. look at the title bar


Actual :
 A speed of less than 1 is shown on title bar.

Expected :
 A speed/tempo ratio shown at title bar should be approximately 1.

Comment 1

[Chris Pearce [:cpearce (Not reading bugmail)]]

Our keyframe skipping logic which we added in the new decoder backend should kick in and ensure that we keep playing audio when the video decode is having trouble keeping up. We should have a smooth timeline progression now (provided enough data is buffered), so I'm closing this bug. Please reopen if this still happens on trunk nightlies.

Comment 2

[u279076]

Finding a PC with low performance will be a challenge.  Marking this verified on faith.  As with comment 1, please reopen if you can reproduce.