[MPlayer-dev-eng] Error in docs? (Preserving aspect ratio)
D Richard Felker III
dalias at aerifal.cx
Sun May 4 23:57:25 CEST 2003
On Sun, May 04, 2003 at 11:19:11PM +0200, Diego Biurrun wrote:
> Jason Tackaberry writes:
> > http://mplayerhq.hu/DOCS/encoding.html rightly suggests to crop out
> > black bars in the original movie source when encoding. It then goes on
> > to suggest that you should preserve the aspect ratio if you use
> > libavcodec. Both excellent practices, which I follow.
> > But as I was reading these docs, I noticed a problem in the proposed
> > command line:
> > $ mencoder sample-svcd.mpg -ovc lavc -lavcopts vcodec=mpeg4:aspect=16.0/9.0 -vop crop=714:548:0:14 -oac copy -o output.avi
> > Now either there is a problem here, or I am misunderstanding something
> > and as a result have messed up all my encodings. :)
> > The problem, as I understand things, is that if you specify a crop
> > region, you must also adjust the aspect ratio for the new size. The
> > cropped region above is no longer 16/9.
> > For a 16/9 DVD, the video source is usually 720x480 which gets scaled to
> > 854x480. So the correct aspect ratio for the above cropped video, where
> > the original is 16/9, is 714*(854/720)/548, or 1.545. The libavcodec
> > option should then be aspect=1.545.
> > Although I think I have a handle on this, and I think the docs are
> > wrong, please do let me know if I'm misguided. :)
> OK, I corrected the docs in 0_90, the web site should get updated in a
> For main we should use the new autoaspect option implemented by Rich.
> The correct command line should be
> $ mencoder sample-svcd.mpg -ovc lavc -lavcopts vcodec=mpeg4:autoaspect
> -vf crop=714:548:0:14 -oac copy -o output.avi
> Rich, could you please document autoaspect in the man page?
Yep, sorry I forgot to do that with my last DOCS commit.
More information about the MPlayer-dev-eng