[FFmpeg-devel] [PATCH] Add a time_base field to AVFilterPad.

[Stefano Sabatini]

On date Saturday 2010-10-09 16:03:23 +0200, Michael Niedermayer encoded:
> On Thu, Oct 07, 2010 at 03:03:38PM +0200, Stefano Sabatini wrote:
> > On date Thursday 2010-10-07 03:08:40 +0200, Michael Niedermayer encoded:
> > > On Wed, Oct 06, 2010 at 11:32:42PM +0200, Stefano Sabatini wrote:
> > > > On date Wednesday 2010-10-06 22:48:16 +0200, Michael Niedermayer encoded:
> > > > > On Wed, Oct 06, 2010 at 10:07:54PM +0200, Stefano Sabatini wrote:
> > [...]
> > > > > > BTW we need to set the timebase in the two ends of a link (either in
> > > > > > the link itself or in the input and output pads) if we want to keep
> > > > > > the timestamp conversion code in the framework rather than in the
> > > > > > filters code.
> > > > > 
> > > > > when does this design simplify filters?
> > > > > do you have an example?
> > > > > it seems simpler to have just one tb per link
> > > > 
> > > > A filter in general may to set the output timebase, and another filter
> > > > the input timebase.
> > > > 
> > > > Think for example of a source, which generates video frames with given
> > > > framerate, or a movie sink which needs to use the same timebase as set
> > > > in the muxer, so I believe this in general is a useful feature that we
> > > > want to keep.
> > > 
> > > the movie sink can contain that 1 line of code to rescale
> > > any other filters that would need that?
> > > 
> > > if not then this really seems the more logic approuch
> > 
> > The problem with the timebase in the link approach is that it may
> > require each filter to automatically check in start_frame()
> > if the input/output link timebases changes accordingly (so we'd have
> > to add code to many already existing filters).
> 
> timebases cannot change, not without reinitalizing the filters IMHO

No I wasn't clear, I mean that each start_frame() should check if
input timebase != output timebase and do the timebase conversion
accordingly.

Note that this will not be necessary most of the times as usually (but
for the settb filter) the input timebase is configured the same as the
output timebase.

Anyway that's not a big problem, as the conversion code is just two
lines and I already implemented the check+conversion in the default
start_frame() code (still waiting for your review).

Regards.
-- 
FFmpeg = Fundamentalist Fancy Mere Pitiless Energized Gem