[FFmpeg-devel] [RFC] v4l2 frame rates

Michael Niedermayer michaelni
Mon Jan 5 20:00:27 CET 2009

On Mon, Jan 05, 2009 at 03:55:42PM +0100, Luca Abeni wrote:
> Hi all,
> the current v4l2 input format requires that the user specifies a
> frame rate for the input. Such frame rate, which can be completely
> wrong, is used for initialising the input codec time base and is
> stored in the video_data structure, but is never actually used...
> So, I think this "feature" should be removed, as in the attached
> patch. After applying the patch, if the user does not specify a
> frame rate the standard "1 us" time base is used (and the input
> codec is considered as variable frame rate).
> But it is still possible to specify a frame rate for the input, to
> avoid the av_find_stream_info() delay (in case of variable frame rate,
> this function always tries to read some packets... The results in a
> 2.5s delay when opening the input).
> I am still unsure if this is the best solution (I think it is an
> improvement respect to the current behaviour, but maybe we can do
> something better...), hence the RFC (yes, I already considered the idea
> of querying the video standard to obtain the correct frame rate... But
> this does not work for some webcams).

i have no objection to the patch

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I wish the Xiph folks would stop pretending they've got something they
do not.  Somehow I fear this will remain a wish. -- M?ns Rullg?rd
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