[MPlayer-users] Syncronization problem

[Giacomo Comes]

On Mon, Dec 20, 2004 at 07:14:15PM +0100, Fabio S. wrote:
> Hi all,
> 
> I have a syncronization problem that I am not able to solve. What seems
> strange to me is that it is generated by mencoder itself.
> 
> I use mencoder to grab videos from my videocamera. 
> Since my machine is not very fast, I use the following strategy: 
> 1) I grab a  video from my videocam with a very high video bitrate 
> and no audio encoding
> 2) I encode the video obtained in 1) compressing audio in mp3 and then 
> doing a
> 2pass encoding for the video with a smaller bitrate.
> 
> The video I get after step 1) is perfectly syncronized.
> 
> After this step the camera is no longer needed and the second step relies 
> only on mencoder; nevertheless, the video I get after the second step 
> is out of sync and the desyncronization increases from nearly nothing at
> the beginning to 3-4 seconds at the end.
> 
> Here are the commands I use:
> 
> Step 1:
> mencoder -endpos 1:00:00 -tv driver=v4l2:input=1 -vf pp=lb -ovc lavc 
> -lavcopts vcodec=mpeg4:v4mv:vbitrate=6000:mbd=2 -oac copy -o "video.avi" 
> tv://
> 
> Step 2:
> mencoder -oac mp3lame -ovc frameno  video.avi -lameopts cbr -o frameno.avi 
> mencoder video.avi -oac copy -ovc lavc -lavcopts 
> vcodec=mpeg4:vbitrate=1600:vpass=1:vhq:mbd=2
> mencoder video.avi -oac copy -ovc lavc -lavcopts 
> vcodec=mpeg4:vbitrate=1600:vpass=2:vhq:mbd=2
> 
> Any suggestion?

Instead of 3 pass encoding try 2 pass (it's equivalent to 3 pass, just a little bit slower):

mencoder video.avi -oac mp3lame -lameopts cbr -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1600:vpass=1:mbd=2 -o newvideo.avi
mencoder video.avi -oac mp3lame -lameopts cbr -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=1600:vpass=2:mbd=2 -o newvideo.avi
(remove vhq because it is equivalent to mbd=1 and you have mbd=2 too)

Does it help?

Giacomo