[Ffmpeg-devel] [PATCH] DVR-MS probe audio format - was DVR-MS bug (MP2 decoding)

Michael Niedermayer michaelni
Fri Mar 16 04:11:15 CET 2007


Hi

On Thu, Mar 15, 2007 at 09:56:52PM -0500, John Donaghy wrote:
> >trying the same check everywhere in a buffer, lets say its 2kb large will
> >cause 1 out of 50 random files to be misdetected as ac3, thats not going
> >to
> >work ...
> 
> 
> OK, I see your point. I can think of three approaches then:
> 
> 1) Improve the ac3_probe function which I think is probably the best way -
> but unfortunately I've no idea how to do it.

search for several valid frames in a row, the AVParser for AC3 can find the
size of each, there should be a matching header immedeatly after that AFAIK
see mp3_read_probe()


[...]
> 3) Since the stream I'm trying to identify can only be MP2 or AC3 maybe I
> could flag it initially as some newly defined value such as
> 'CODEC_DVR_AUDIO_UNKNOWN' and then in av_find_stream_info set the codec to
> AC3 if it isnt MP2 after several frames have been read. The mp3_probe
> function seems to work reliably for these streams.

iam not against a mp3 fails assume ac3 case but iam against adding 
a CODEC_DVR_AUDIO_UNKNOWN codec id ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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