[Ffmpeg-devel] Re: [PATCH] seeking in GXF

Baptiste Coudurier baptiste.coudurier
Thu Aug 3 10:14:01 CEST 2006


Reimar D?ffinger wrote:
> Hello,
> On Tue, Aug 01, 2006 at 11:13:56PM +0200, Baptiste Coudurier wrote:
>> Demuxer must set time rate if it knows it and GXF specifies it. Some
>> codecs can't set the frame (MJPEG for example) cause it simply does not
>> have this information.
> Well, I think as you have seen in our discussion on IRC, GXF does
> specify it sometimes. Somewhat. Maybe.
> Or more precisely: There is a precise fps value in the special tag for
> it. But that is not necessarily present. The one if UMF is always
> present, but not necessarily precise (24 fps and 23.98 fps is coded the
> same way).
> I just don't really like the idea of overwriting the correct value that
> the MPEG2-decoder would detect by a possible imprecise value from the
> demuxer. And I also don't like special-casing MPEG2.
> So you think that just setting e.g. 24 fps even if it might really
> be 23.98 fps would be best?

Humm no, after further investigation, it seems only mplayer plays it
twice speed. ffplay just plays it fine, and the code is doing what must
be done, dunno why mplayer does that.

Btw, I had to let decoder init parameters for some codecs in mov: aac,
mp3on4, vorbis and there is no way other than manually setting sample
rate to 0 while it was specified in container.

That to mean special casing MPEG-2 is IMHO harmless when it's indeed
better to let decoder init params.

Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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