[EMAIL PROTECTED] (Andrew Church) wrote:
> This is in fact mentioned on both the examples page and the main aspect
> ratio page;
Good, thanks.
> However, it is not (to the best of my knowledge) compatible with all
> players, so I do not make use of it in the examples.
I already heard about this argument, but I'm wondering whether it's
still valid nowadays. First, AFAIK, not supporting this PAR is a plain
bug in the video players, since it's a feature defined in the MPEG-4
standard, just as the one for DVDs (what would you say of a player
displaying all DVDs with a 1:1 PAR?...). Second, IIRC, this PAR setting
is recognized by:
- recent MPlayer/ffmpeg (I don't know if it's actually implemented in
the ffmpeg MPEG-4 decoder or in MPlayer itself, and I don't know
about old ones);
- vlc in Debian sarge and sid;
- kaffeine in Debian sid.
These are the only players I tested with. Unfortunately, this setting
isn't always preserved during conversions (transcoding from such a
PAR-enabled MPEG-4 file to MPEG-2 TS by VLC for the Freebox
[http://en.wikipedia.org/wiki/Freebox] doesn't preserve the PAR,
unfortunately).
But there is another way of setting the PAR in an AVI file, using an
extension of the AVI format, and this one is much *less* portable IME.
It is achieved with the -force-avi-aspect of mencoder:
,----[ mencoder(1) ]
| -force-avi-aspect <0.2-3.0>
| Override the aspect stored in the AVI OpenDML vprp header. This
| can be used to change the aspect ratio with '-ovc copy'.
`----
So, we have to make sure people don't confuse these two ways of setting
the PAR in AVI files:
- in the AVI container, through an extension, which seems non-standard
and badly supported;
- directly in the video stream for codecs that support it, such as
those defined in MPEG-2 and MPEG-4 (and also MPEG-1, according to
mplayer/doc/HTML/en/aspect.html); this way is standards-compliant
AFAICT, and apparently better supported than the other one, even if
not perfectly.
--
Florent
