[MPlayer-users] mpeg2video, frame rate

[Andres Heinloo]

On Wed, 4 Feb 2004, D Richard Felker III wrote:

> On Wed, Feb 04, 2004 at 06:07:40PM +0100, Andres Heinloo wrote:
> > 
> > 
> > On Wed, 4 Feb 2004, Andres Heinloo wrote:
> > 
> > > The problem is that mpeg2video apparently does not set the frame rate in
> >                                                              ^^^^^^^^^^
> > Sorry, I meant bitrate.
> > 
> > > the header, which confuses some software. What is the easiest way of
> > > filling this field in the header of m2v file? I cannot use, eg., mpeg2enc,
> > > because the source video has uneven framerate.
> > > 
> > > I would also appreciate any tipps for fixing the framerate (inserting
> > > duplicate frames or skipping frames where needed). I was trying this:
> > > 
> > > mencoder in_file.mpg -ofps 29.97 -ovc lavc -lavcopts vcodec=mpeg2video:vqscale=2:vhq -oac copy -of mpeg -o out_file.mpg
> > > 
> > > (followed by dumpvideo, dumpaudio, mplex).
> > 
> > I mean, is there a way to normalize the frame rate (insert/remove frames)  
> > without re-encoding the video?
> 
> In principle, adding duplicate frames is easy, but afaik mencoder
> can't do it right.
> 
> Also in principle, you can remove frames, but it requires some
> reencoding. The naive way is the reencode up to the next keyframe, but
> it should be possible with advanced software to remove a single P
> frame and replace the next P frame with one that combines the changes
> from the two... Anyway this is difficult and requires very specialized
> software, so don't expect it anytime soon.
> 
> > Is vqscale=2 sensible (I want the output to
> > be in size and quality as close to the input as possible)?
> 
> Probably not. It could be much larger than the original, and won't
> meet the bitrate constraints for DVD/SVCD/whatever.
> 
> Rich

Thanks for the answer. In fact, duplicate frames is all I would need (the
original video never exceeds 29.97 fps). But setting the correct bitrate
of mpeg2 stream would be also extremely helpful...

Andres.