[theora] ffmpeg2theora bug: generation of a video from a series of images

Basil Mohamed Gohar abu_hurayrah at hidayahonline.org
Fri Mar 5 06:44:56 PST 2010

On 03/05/2010 09:13 AM, Basil Mohamed Gohar wrote:
> On 03/05/2010 01:26 AM, Michael Opdenacker wrote:
>> Hi J.,
>> We are using ffmpeg2theora to produce an introduction video from a
>> series of images:
>> ffmpeg2theora-0.26.linux32.bin images/img-%03d.png -o intro.ogv
>> The video that we get is huge and horrible, with lots of blinking colors:
>> http://free-electrons.com/issues/ffmpeg2theora-mar5-2010/intro.ogv
>> Here's what we had in the past:
>> http://free-electrons.com/issues/ffmpeg2theora-mar5-2010/intro-correct.ogv
>> This issue was introduced in ffmpeg2theora-0.25, and a work-around is to
>> revert to ffmpeg2theora-0.24
>> (http://v2v.cc/~j/ffmpeg2theora/ffmpeg2theora-0.24.linux32.bin.bz2). I
>> also checked that this problem still happens with the latest snapshot
>> release.
>> All you need to reproduce this bug is in
>> http://free-electrons.com/issues/ffmpeg2theora-mar5-2010/
>> Even though the bug may not be in ffmpeg2theora, it would be great if
>> you could fix it. Don't hesitate to ask me to make further tests if this
>> can help.
>> Thanks for this very useful utility,
>> Cheers,
>> Michael.
> I just tested this image sequence using png2theora from ptalarabvorm,
> and I also got some weird outlining of the text as well as some
> flashing.  This image sequence looks like a great test for Theora!
> It is a high-contrast text + graphics image that is not overly complex. 
> It fades-in from black and then fades-out to black again.
> I'm sorry this doesn't actually address your concern, though.  But I'm
> sure we'll find a solution.
Okay, I just ran all the PNG images through optipng after noticing that
they had an alpha channel.  Also, ffmpeg reported they were in bgra
format (the "a" is for alpha, but I don't know why they were bgr
order).  I ran it through png2theora again, after this lossless (for the
purposes of this test) processing, and I got a smaller video file
without the corruption.  So, my first advice to you is to run the images
through optipng and try again.

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