[MPlayer-users] MPlayer-1.0pre8 detecting wrong aspect ratio

[Giacomo Comes]

On Mon, Jul 31, 2006 at 06:08:55PM +0200, Nico Sabbi wrote:
> Giacomo Comes wrote:
> >>>I use a script for encoding with mencoder. The script reads the aspect
> >>>ratio from the output of -identify. Now with this problem, the script
> >>>fails to detect the aspect ratio, and I am having to provide it
> >>>manually.
> >>>      
> >>if it's wrong it's wrong
> >>    
> >
> >No Nico,
> >1.0pre8 and current svn have a BUG.
> >The bug consists in the fact that mplayer does not detect correctly the
> >aspect ration of MPEG1 streams.
> >
> >Example 1: 4/3 (1.33:1) PAL MPEG1 stream
> >VIDEO:  MPEG1  352x288  (aspect 2)  25.000 fps  1152.0 kbps (144.0 kbyte/s)
> >
> >1.0pre8 plays it as:
> >Movie-Aspect is 1.81:1 - prescaling to correct movie aspect.
> >VO: [xv] 352x288 => 522x288 Planar YV12
> >
> >1.0pre7 plays it as:
> >Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
> >VO: [xv] 352x288 => 384x288 Planar YV12
> >
> >
> >The bug is not limited to 4/3 aspect ratio. Also 16/9 is misdetected.
> >As already said, this bug breaks also any script that use mplayer to 
> >retreive the aspect ratio of a movie (therefore a quick fix is welcome).
> >
> >Giacomo
> >_______________________________________________
> >  
> 
> what I changed in pre8 is the assignment of the A/R code; I moved it 
> from the
> demuxer domain (where it was totally out of place) to the video decoder 
> layer
> (where it belongs).
> Previously the A/R assignment was completely wrong for mpeg1, because it 
> was
> assigned as for mpeg2.

I'm sorry to say but it's the opposite. Previous assignment was correct, 
current one is wrong. Not because I have seen the code, just because the
previous one was working and the current one is not.

> 
> Post some link to samples and we'll see what we can do :)

You can download MPEG1 samples from:
http://www.pcphotovideo.com/VcdSamples.htm

or make your own:
mencoder <your souce video> -of mpeg -mpegopts vaspect=4/3:format=xvcd -ovc lavc -lavcopts vcodec=mpeg1video:vrc_buf_size=327:vrc_minrate=1152:vrc_maxrate=1152:keyint=15:aspect=4/3:vbitrate=1152 -o mpeg1pal.mpg -ofps 25 -vf scale=352:288,harddup -oac lavc -lavcopts acodec=mp2:abitrate=224 -frames 100

mencoder <your souce video> -of mpeg -mpegopts vaspect=4/3:format=xvcd -ovc lavc -lavcopts vcodec=mpeg1video:vrc_buf_size=327:vrc_minrate=1152:vrc_maxrate=1152:keyint=18:aspect=4/3:vbitrate=1152 -o mpeg1ntsc.mpg -ofps 30000/1001 -vf scale=352:240,harddup -oac lavc -lavcopts acodec=mp2:abitrate=224 -frames 100

Giacomo