[MEncoder-users] mencoder: mp2->mp4 autoaspect question

[Toerless Eckert]

I am using mencoder to convert TV mpeg2 recordings to mpeg4:

   -vc mpeg12 -ovc lavc -lavcopts vcodec=mpeg4:v4mv:autoaspect:... 

This works only to a degree: the mpeg4 file seems to get the aspect
ratio that the mpeg2 input file has at the beginning (16:9 or 4:3),
but when the aspect ratio changes within the input mpeg2 file, then
this does not correctly gets translated into the mpeg4 file.

What is see is that both xbmc and vlc will correctly switch to the initial
aspect ratio at the beginning of the file, but not during the ongoing playback
of the file. On the other hand, they do correctly change the aspect ratio
while playing the original mpeg2 files.

I encode the mpeg4 files with avi header, so the aspect ratio does not come
from the file header.

Is this supposed to work with mencoder ?
If not, how difficult would it to add this to mencoder ?

Thanks
    Toerless