Theora playback problems
OS: Windows XP Pro 32 bits
VLC build used: http://www.jbkempf.com/~jb/vlc-1.0.0-git-20090211/
Problems with Theora videos:
http://www.raoulpetite.com/videos/sable.ogg
Vertical green artifacts on the left. MPlayer is showing the same artifacts though.
http://samples.mplayerhq.hu/V-codecs/Theora/Sahara.ogg
Horizontal green line at the bottom. MPlayer is playing it fine without any artifacts.
Some videos are playing fine though without any artifacts: http://samples.mplayerhq.hu/V-codecs/Theora/Yeager_supersonic_flight_1947.ogg
But in all cases, the total time displayed by the counter is wrong:
8:52 total time for the Raoul Petite video while real duration is 4:35
0:02 total time for the Sahara video while real duration is 0:15
11:46 total time for the Chuck Yaeger video while real duration is 3:03
Some videos don't even show a total time: http://samples.mplayerhq.hu/V-codecs/Theora/WobblyWindowsIntro.ogg
Activity
added Component::Decoders Severity::normal Type::bug Version::master git labels
changed milestone to %1.0 bugs
sable.ogg: looks like broken video to me
Sahara.ogg: 240x144 8.00 fps video, frame content is 240x136 with offset (0,8) main video output debug: window size: 240x136 opengl video output debug: Texture size: 240x144 This sample behaves correctly I think. It appears as if mplayer does not respect the frame offset settings. (not many players do). I need to verify to be sure, that we respect offset correctly, but we pass the theora testsuite which tests these things, so I think we show the correct behaviour.
Duration of theora samples is a known issue (and longstanding). has to do with the bitrates reported in the file that we use to calculate duration. The only other way to calculate duration properly is to preparse the file, or the file needs to have a skeleton track.
About Sahara.ogg. It defines an encoded videosize of 240x144. The actually usable and desired video framesize is 240x136. (Theora only allows encoded video sizes that are a multiple of 16pixels). The file then specifies an offset of 8 pixels on the Y axis. This offset is defined as being based on the lowerleft corner of the displayframe. As such it moves this lowerleft corner 8 pixels higher, thus again exposing the pixels that were meant to be cropped, and instead cropping the top 8 pixels from the displayframe. Likely cause for such a cropping issue is that the specification of "offset" in the Theora videoformat is based on the topleft corner, whereas the libtheora specifies bottomleft corner as base. This opens the door for incorrect implementations in applications. In my opinion however, VLC behaves correctly in this case.
This thus only leaves the duration, which is a known issue of our ogg demux. That makes this a duplication of #1859 (closed)
added Status::duplicate label
