[FFmpeg-soc] [soc]: r329 - libavfilter/TODO

[Bobby Bingham]

On Sat, 7 Jul 2007 09:36:10 +0200
"Víctor Paesa" <victorpaesa at googlemail.com> wrote:

> Hi,
> 
> On 7/6/07, koorogi  wrote:
> > Log:
> > update TODO list a bit
> 
> > --- libavfilter/TODO    (original)
> > +++ libavfilter/TODO    Fri Jul  6 19:55:52 2007
> > @@ -1,10 +1,9 @@
> >  FRAMEWORK:
> > -- colorspace negotiation
> > +- can colorspace negotiation be improved?
> >  - auto-inserting needed filters (colorspace conversion, buffer,
> > etc) -- parameter passing
> > +- parameter passing (can this be done better with AVOption?)
> >  - pass pts, and whatever info is needed to reorder decode ordered
> > frames
> >  - other useful image flags?  interlace?  top/bottom field first?
> > -- rework init sequence
> >  - ease reuse of same memory for multiple slices
> >
> >  - proper vout filter support, with a display() callback?
> 
> I was wondering if would be possible to pass a bit more of context to
> the filters.
> I am thinking on an AVStream * to the original stream passed on to the
> filter chain.
> 
> The scenario is a filter to fade out the last few seconds of a movie.
> If you pass the AVStream *, the filter might get the estimated movie
> duration by itself.

I've thought about this a little.  I do think there needs to be a way
to pass data of such to the filters, but I'm not sure about passing an
AVStream * itself.  For example, right now I'm using a filter which
generates a sequence of frames for testing - I can foresee other cases
where there may not actually be an AVStream associated with the filter
chain.

Also, if such a fadeout filter is at the end of the filter chain, and
another filter adjusts timestamps (2x speedup for example), the length
of the stream won't match what the fadeout filter itself will see.

I think instead it may be better to have an entry point in the filters
to get such metadata, process it, and pass it along to the next
filter.  So, the program could pass the length of the stream to the
first filter, which would pass it up the chain to the next filter, and
so on.  If there was a 2x speed filter, for example, it could pass the
adjusted running to the next filter.

> 
> Regards,
> Víctor

-- 
Bobby Bingham
Never trust atoms.  Or anything made of atoms.
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