[MEncoder-users] rotate an MP4

[Moritz Barsnick]

On Fri, Jul 03, 2009 at 18:32:44 +0200, Daniel Kirsten wrote:

> One can observe a loss of quality.   (I played the original and the
> rotated movie simultaneously.)

This is always the case if you de- and recode a video. Even if one of
the intermediate steps is lossless (jpegtran).

Actually, you are at more loss than necessary. You decode MPEG4, encode
to JPEG (additional loss), decode JPEG, then encode to MPEG4
(additional loss). You could just decode MPEG4 and reencode it after
rotation. For the rotation step, use the "-vf rotate" video filter.

Furthermore, it has been stated that MPEG4 _theoretically_ even
supports lossless rotation (like JPEG), just no software implements
that:
http://lists.mplayerhq.hu/pipermail/mplayer-users/2008-April/072847.html
Tough luck. ;-)

> The file is 10-20 percent larger than the original file.

That depends on your coding parameters.

Moritz