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

[Michael Niedermayer]

On Fri, Oct 01, 2010 at 11:38:59AM +0200, Stefano Sabatini wrote:
> On date Friday 2010-10-01 11:12:44 +0200, Stefano Sabatini encoded:
> > On date Friday 2010-10-01 01:27:36 +0200, Michael Niedermayer encoded:
> > > On Thu, Sep 30, 2010 at 10:35:41PM +0200, Stefano Sabatini wrote:
> > > > On date Tuesday 2010-09-28 20:29:48 +0200, Michael Niedermayer encoded:
> > > > > On Tue, Sep 28, 2010 at 02:34:05AM +0200, Stefano Sabatini wrote:
> > [...]
> > > > > > So we have this scenario:
> > > > > > 
> > > > > > buffer [TB1] <-> [X] filter [Y] <-> [Z] ffmpeg_output
> > > > > > 
> > > > > > Z can be set using the TB provided in the output video stream, so we
> > > > > > have:
> > > > > > 
> > > > > > buffer [TB1] <-> [X] filter [Y] <-> [TB2] ffmpeg_output
> > > > > 
> > > > > X=TB1
> > > > > Y=X unless filter wants something else
> > > > > Z=Y
> > > > > ffmpeg has to configure itself to use Z or rescale, there never is a timebase
> > > > > moving backward in the graph
> > > > > 
> > > > > or in other words i fail to see where the problem you seem to have comes from
> > > > > but i might be missing something of course
> > > > 
> > > > Updated patch implements this logic.
> > > > Example:
> > > > 
> > > > $ echo "color,null,null,settb=23:35,null,settb=365:234,null,null,nullsink" | tools/graph2dot
> > > > digraph G {
> > > > node [shape=box]
> > > > rankdir=LR
> > > > "Filter 0 color (color)" -> "Filter 1 null (null)" [ label= "[1/1000000] fmt:argb w:320 h:240 [1/1000000]"];
> > > > "Filter 1 null (null)" -> "Filter 2 null (null)" [ label= "[1/1000000] fmt:argb w:320 h:240 [1/1000000]"];
> > > > "Filter 2 null (null)" -> "Filter 3 settb (settb)" [ label= "[1/1000000] fmt:argb w:320 h:240 [23/35]"];
> > > > "Filter 3 settb (settb)" -> "Filter 4 null (null)" [ label= "[23/35] fmt:argb w:320 h:240 [23/35]"];
> > > > "Filter 4 null (null)" -> "Filter 5 settb (settb)" [ label= "[23/35] fmt:argb w:320 h:240 [365/234]"];
> > > > "Filter 5 settb (settb)" -> "Filter 6 null (null)" [ label= "[365/234] fmt:argb w:320 h:240 [365/234]"];
> > > > "Filter 6 null (null)" -> "Filter 7 null (null)" [ label= "[365/234] fmt:argb w:320 h:240 [365/234]"];
> > > > "Filter 7 null (null)" -> "Filter 8 nullsink (nullsink)" [ label= "[365/234] fmt:argb w:320 h:240 [365/234]"];
> > > > }
> > > > 
> > > > It is not yet clear to me how to interpret this sentence from you:
> > > > 
> > > > |by default the output tb should be choose so that all input timestamps can be
> > > > |exactly represented or if this timebase exceeds 32/32bit then AVTB
> > > 
> > > a filter  that has 2 inputs has 2 input timebases ...
> > > ill review your patch once you confirm that its supposed to work in such cases
> > 
> > Still it's not clear what you mean by "exceeds 32/32bit". Check how
> > I'm managing pts conversion in this variant of the overlay filter,
> > in particular the config_output() function.
> > 
> > $ echo "nullsrc=300:300:75/23 [in], nullsrc=128:246:29/37 [over]; [in][over] overlay, nullsink" | tools/graph2dot | dot -Tpng -o out.png; display out.png
> > [nullsrc @ 0xa38b150] w:300 h:300
> > [nullsrc @ 0xa38b390] w:128 h:246
> > [overlay @ 0xa38b650] main w:300 h:300 fmt:yuv420p overlay x:0 y:0 w:128 h:246 fmt:yuva420p
> > [overlay @ 0xa38b650] main_tb:23/75 overlay_tb:37/29 -> tb:851/2175 exact:1
> > 
> > Regards.
> 
> [...]
> > +static int config_output(AVFilterLink *outlink)
> > +{
> > +    AVFilterContext *ctx = outlink->src;
> > +
> > +    /* choose the output timebase */
> > +    AVRational tb1 = ctx->input_pads[MAIN   ].time_base;
> > +    AVRational tb2 = ctx->input_pads[OVERLAY].time_base;
> > +    AVRational tb;
> 
> > +    int exact = av_reduce(&tb.num, &tb.den,
> > +                          tb1.num * tb2.num, tb1.den * tb2.den, INT_MAX);
> 
> And soon I realized this may overflow.

you are missing int64_t casts

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

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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