Correction: The playback differences appeared in the Debian version of Firefox 3.5.16; the nightly builds of Firefox play the video without hesitations.
On Thu, February 17, 2011 12:19 pm, George Chriss wrote:
Hi Lars,
A cursory look suggests the problem originates in Firefox's internal decoding, even using the most-recent nightly builds. Furthermore, the problem only is apparent when the video is played from within a Commons page ( http://is.gd/mWpoap ); viewing the video directly works just fine ( http://is.gd/gn0BEr ).
Comment #5 from Mozilla bug #531279 ( http://is.gd/m9pqZ5 ) suggests the problem might be somehow related to video re-scaling, but it might be better to file a new bug and see what happens. I'd be happy to help submit the bug report if needed.
Sincerely, George
On Thu, February 17, 2011 5:25 am, Lars Aronsson wrote:
In Firefox 3.6.13 on Linux, I can show Ogg Theora videos just fine, which is a great step forward from earlier versions a year ago. But there are still bugs, where the playback just hangs. I have no way to tell if this is a poorly encoded video or a browser bug or something relating to my screen driver. All I know is that it happens more often for videos with higher bitrate. As a programmer, I could guess that there is some buffer competition, a combination of buffer boundaries and time racing, that causes a deadlock. I have no way to know the reason or whether it is unique to me. Too few people watch videos in Wikipedia, so I have no user base to draw conclusions from. The source code is available, but I don't want to take the time to specialize in video decoding. This headache is already taking far too much of my time.
For one video, I changed the encoding and this made the problem occur less frequently for me. This 720 x 544 pixel, 15 minute video was 116 MB when first encoded with "ffmpeg2theora" without parameters, so to make it pass under the 100 MB limit I added "-v 4" (lowercase v for video quality), to slightly reduce the video quality. But it hanged just too often, and by encoding with "-V 600" (uppercase V for bitrate, 600 kbit/s), it runs a lot more smooth on my laptop. You can try either version at http://commons.wikimedia.org/wiki/File:M%C3%A4n_och_maskiner_1936.ogv
Looking at these 1200 Dutch videos, http://commons.wikimedia.org/wiki/Category:Media_from_Open_Beelden they are just 320x240 pixels, which is another way to get smaller files and lower bitrates.
Is that something I should settle for? Will I live happier and prosper if I scale all videos to half their size? Maybe in 2-3 years time, when the 100 MB limit has been lifted and Firefox 4.x offers a more mature video playback, we can upload the same videos in better resolution?
Should we make this a recommendation? Do we have statistics on the resolution and bitrate of the videos on Commons?
Who did the job with the Dutch films? How did they reason?
-- Lars Aronsson (lars@aronsson.se) Aronsson Datateknik - http://aronsson.se
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