[FFmpeg-devel] Could this be a SOC project? mkv to mp4 ps3 tweaks

Michael Niedermayer michaelni
Thu Mar 19 17:05:37 CET 2009

On Thu, Mar 19, 2009 at 10:52:55AM -0500, John Lange wrote:
> I just joined this list to ask questions about how to do the following
> work on ffmpeg but I stumbled on the thread about GSOC projects.
> Here is the description of what I want to do but perhaps this is a good
> candidate for SOC?

its a great candidate as a qualification task

a SOC project could be redesigning the timestamp handling in ffmpeg.c
to make it more robust against inavlid and or missing timestamps as well
as timestamp discontinuities

> However, if you first demux the file with mkvextract into a video and
> audio track, it works:
> # mkvextract tracks input.mkv 1:input.video 2:input.audio 
> # ffmpeg -i input.video -i input.audio -vcodec copy -acodec libfaac output.mp4
> 2) Unfortunately the resulting file often will still not play on the PS3
> because for some reason almost all mkv files have their h264 video set
> to level 5.1 even though they contain nothing that requires this high
> setting. In my testing I've found that in many cases a simple hex edit
> of the source h264 stream to change it to 4.1 fixes this problem and it
> then plays just fine.
> Unfortunately there is no way to change the level with ffmpeg unless you
> transcode the entire h264 stream. So instead of taking a few seconds or
> minutes it can take days.
> I'm thinking the solution might be to allow "-vcodec copy" to still
> accept options which don't require transcoding. So for example:

the solution is to write a bitstream filter that can change these parameters


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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