[FFmpeg-devel] [PATCH] Fix ratecontrol bug when time_base.num > 1

[Michael Niedermayer]

On Fri, Nov 16, 2012 at 04:01:26PM +0000, Joseph Artsimovich wrote:
> On 16/11/2012 15:28, Kieran Kunhya wrote:
> >>I dont fully understand the problem, so its hard to suggest how to
> >>fix it.
> >The problem is his application doesn't like the timebase as a reduced
> >fraction, but would rather
> >have it as a reducible fraction.
> >
> Not quite. That's only part of the problem. The following line of
> code from ratecontrol.c:
> 
> wanted_bits = (uint64_t)(s->bit_rate*(double)dts_pic->f.pts / fps);
> 
> won't work correctly for any time_base where numerator is greater
> than 1, as it doesn't consider the scale of dts_pic. For instance,
> it will fail on your typical NTSC timing of 1001/30000. Now, the
> obvious fix is to include s->avctx->time_base.num into the
> denominator of the above line of code. That would fix the NTSC case,
> but not my case, which was 24/600, as s->avctx->time_base gets
> automatically reduced to 1/25. Therefore, I went with s->dts_delta
> instead of s->avctx->time_base.num. However, Michael explained it's
> not suited for that purpose.

fps is calculated as 1.0 / av_q2d(avctx->time_base) / FFMAX(avctx->ticks_per_frame, 1);
that is supposed to take the numerator already into account.

also 24/600 or 1/25 the timestamps should be 1,2,3,4,...

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

You can kill me, but you cannot change the truth.
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