[MEncoder-users] lavc & h.264

[Raimund Berger]

Philippe MONROUX <phi2-monroux at wanadoo.fr> writes:

>> > First, autoaspect has little or nothing to do with speed. 
>
> http://www.mplayerhq.hu/DOCS/HTML/en/aspect.html
>
> 13.10. Preserving aspect ratio
> ...
> Rescaling the movie is disgusting and
> time consuming, there has to be a better way! 
> ^^^^^^^^^^^^^^

Rescaling might be ugly in some cases, but depending on the bitrate you
can spend on your video it could help picture quality. Scaling down
video in low bitrate situations is common practice for a reason.

Also, scaling is usually far less time consuming than encoding.

That said, the aspect ratio has little to do with that. You scale video
with the "scale" option and crop it with "crop". If you do either or
both, you generally change the aspect ratio of the video, which has to
be recomputed to store that attribute in the target video stream
resp. container. Computing the new AR is just a tiny little helper
function, which does it's job in a split second.

So if you don't want to scale, don't use "scale".

Also, last time I checked, if you do not use lavc but the builtin x264
stub (-ovc x264), mencoder does compute the correct aspect ratio anyway
and stores it in the target video stream, as pixel aspect ratio
(PAR). So if autoaspect is the only reason you want to use lavc, to all
my knowledge you don't even need that for x284 encodings.