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

[Michael Niedermayer]

On Sun, Oct 03, 2010 at 11:23:49PM +0200, Stefano Sabatini wrote:
> On date Sunday 2010-10-03 21:07:55 +0200, Michael Niedermayer encoded:
> > 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
> 
> Ok so the overlay config_output would be:
> 
> 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 = 1;
> 
>     exact *= av_reduce(&tb1.num, &tb1.den, tb1.num, tb1.den, INT32_MAX);
>     exact *= av_reduce(&tb2.num, &tb2.den, tb2.num, tb2.den, INT32_MAX);
>     exact *= av_reduce(&tb.num, &tb.den,
>                        (int64_t)tb1.num * tb2.num, (int64_t)tb1.den * tb2.den, INT_MAX);

your code makes no sense
with a/b and c/d

you need something like:
reduce(gcd(ad,cb)/bd)

[... ]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Incandescent light bulbs waste a lot of energy as heat so the EU forbids them.
Their replacement, compact fluorescent lamps, much more expensive, dont fit in
many old lamps, flicker, contain toxic mercury, produce a fraction of the light
that is claimed and in a unnatural spectrum rendering colors different than
in natural light. Ah and we now need to turn the heaters up more in winter to
compensate the lower wasted heat. Who wins? Not the environment, thats for sure
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20101004/94d7db94/attachment.pgp>