[MEncoder-users] cutting mpeg-2

[Giacomo Comes]

On Mon, Dec 03, 2007 at 09:23:55AM -0800, Pawel K wrote:
> > > Hello
> > > I have the mpeg-2 file and want to cut it without
> > > decompressing it. The I-frame cut resolution suits
> > me.
> > > I use the following command:
> > > 
> > > mencoder -ss 0 endpos 10 -ovc copy -oac copy
> > > source.mpg -o result.mpg
> > > 
> > > The result.mpg contains exactly 10 seconds from
> > the
> > > beginning of the source.mpg.
> > > 
> > > I found that a few frames around frame nr 50 have
> > > strange rectangles, they are a bit distored.
> > > 
> > > I tried to cut the movie in other arbitrary
> > locations
> > > and had always the same distored frames at around
> > > 50th.
> > > 
> > > How can I cut the movie with mencoder without need
> > to
> > > decompress it.
> > > 
> > > thank You for help.
> > 
> > Adding -mc 0 should fix your problem.
> 
> Thanks a lot. Indeed it solved the problem :)
> but I found that 3 first frames are blank, 4th and 5th
> is a bit distorted and the remaining ones are OK.
> 
> Doesn't matter whether I cut it at the beginning or in
> the middle of the movie.
> 
> I think that's because I use the "-ss <sec>" mencoder
> option to select the cut point.

Looks like a bug. rc1 does not have this problem.

> I should cut it at exactly the I-frame.
> Right ?

This is exactly what normally happens.
You don't need to specify "cut at the closest I-frame"

I will try to figure out when the bug was introduced.

Giacomo

> 
> How to locate the closest I-frame ?
> How to cut at the exact I-frame ?
> 
> thank You for help