[FFmpeg-devel] VP6 issues in Swfdec

Benjamin Otte otte
Sun Sep 9 13:57:42 CEST 2007

Aurelien Jacobs <aurel <at> gnuage.org> writes:

> I want to reproduce the issue, but I want to do it with ffmpeg/ffplay
> (instead of swfdec). As the swf demuxer don't support compressed swf,
> I tried to convert the samples using swf2flv (from FLV::Info). It
> failed to convert some of the samples, so I wasn't able to test
> everything.
The reason I didn't post these files as FLV or something else ffmpeg could
easily digest is because there is no tool that does it properly, in particular
for the Flash files I posted with embedded videos. I had hoped you could just
grab swfdec, compile and test it. Debian and Ubuntu have packages for Swfdec, 

What I could do is just write(2) the buffers I feed to avcodec_decode_video() to
somewhere else. Is there a way to easily write out stuff so ffplay can read it
back in? Some simple container format for VP6?

> (BTW: any information about compressed swf format would be appreciated,
> is it simply a zlib compressed swf or something like that ?)
That one is easy: If the header starts with "CWS" instead of "FWS", the first 8
bytes are uncompressed, the rest is zlib compressed.

> (BTW, already said in previous review, but please don't use tabs in
> your patches)
Yeah sorry about that. I'm absolutely not familiar with ffmpeg code or coding
styles. Just thought I'd take a quick look to see if I could fix the crashers.

> I don't like it very much. Moreover it probably has a significant
> impact on performances. So at least a benchmark would be needed
> (+ taking care of all remarks in other reviews).
Dunno. I'm more concerned with my code not crashing, since a Flash player
crashing takes down the browser. And I know I'm not the only one that gets
annoyed if a broken Flash video ad kills Firefox. So if there is a way to make
sure ffmpeg doesn't do out-of memory reads there, I'm all for it.
Oh, and sorry for removing the inline. I had removed them for easier
debuggability and forgot to readd them when preparing the patches.

> [rest of review]
I think I'll blame the converter for not converting the videos correctly. There
is unfortunately not a lot of Free code that does more than the basics of Flash.


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