GNOME Bugzilla – Bug 431017
mp4 movies with incorrect aspect ratio
Last modified: 2008-10-29 16:31:40 UTC
Hi, this bug was reported as https://bugs.launchpad.net/ubuntu/+source/totem/+bug/103038 "Mplayer (and other players) incorrectly display mp4 movies. The aspect ratio is wrong. By running mplayer with -aspect one can get it to display correctly. Example mp4: http://download.streampower.be/vrt/psp/emma/emma_afl055.mp4 " When running mplayer with -v it reports the correct aspect ratio (2:1) somewhere in between but doesn't use it so it's probably not the file that is broken. Someone knowing more about mp4 please have a look :) Also I don't know if it's gst-ffmpeg or qtdemux that should read the aspect ratio thus Component==don't know Bye
The aspect ratio encoded in the video is 16:9, the demuxer says 1:1. The algorithm for choosing the most likely correct aspect ratio is taking the non 1:1 aspect ration and in case of doubt, use the decoder aspect ratio. This does not work for this movie, which is actualy to be displayed in 1:1. not sure how to fix this. QuickTime specifies that all movies are to be displayed as 1:1 unless otherwise specified with an pasp atom. Maybe this algorithm might work better: - demuxers that force or know about an aspect ratio specify it on their caps, decoder prefers demuxer aspect ratio over its own. - demuxers that have no clue about aspect ratio, don't specify anything and let the decoder select one.
This bug can be closed and marked as INVALID. I just played the video in Quicktime and there it's also displayed too wide, the same as with GStreamer. It's actually the video which has the wrong values set (mp4dump shows display dimensions of 654x208).
It seems that no player I tried (vlc, mplayer, xine, gstreamer) can guess the aspect ratio correctly. Assuming unfixable then.