[MEncoder-users] MEncoder and computation of frame-by-frame decoding time

[Moritz Barsnick]

Hi Andrea,

On Tue, Apr 01, 2008 at 12:22:55 +0200, Andrea Guidi wrote:

> 1) given a certain resolution in input for an avi file, what are the only
> significant resolutions for coding in mpeg2 such that the video is still
> mpeg2 "compliant" and aspect ratio is not altered?

I may be wrong, but  last time I searched for answers to a similiar
question, I found the only possible constraint to be in the profiles
and levels:
http://en.wikipedia.org/wiki/MPEG-2#Video_profiles_and_levels
And MPEG1 may even allow most anything:
http://en.wikipedia.org/wiki/MPEG-1#MPEG-1_video

MPEG containers don't only support the DVD pixel aspect ratios, but
also 1:1, so if you care to preserve your Xvid resolution (it always
uses 1:1, right?), you're free to do so.

> I ask you this because I've chosen the resolutions for mpeg2 format
> specified in the paragraph "Format Constraint" in that page of the link
> above but some of them are not "significant"...what's the principle to
> follow in order to choose mpeg2 resolution?

Well, first of all, you'd have to say which format you would like to
constrain to. If it's just for a software player, almost any resolution
seems feasible, and possibly any framerate as well (not quite sure
here).

Moritz