[MPlayer-users] mpeg2video, frame rate

[D Richard Felker III]

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