[FFmpeg-devel] [PATCH] avcodec/nvenc: fix b-frame DTS behavior with fractional framerates

[Kyle Manning]

I have submitted a v2 patch to instead use the NVENC context's framerate
numerator instead of time_base. Since this value is used everywhere else,
it should theoretically be safe to assume is valid either way. I've also
removed the sign-off, as it was added by mistake when I was fumbling with
git send-email.

- Kyle Manning


On Sun, Apr 2, 2023 at 3:58 PM Hendrik Leppkes <h.leppkes at gmail.com> wrote:

> On Mon, Apr 3, 2023 at 12:25 AM Timo Rothenpieler <timo at rothenpieler.org>
> wrote:
> >
> > On 03.04.2023 00:02, tt2468 wrote:
> > > When using fractional framerates (or any fraction with a numerator !=
> 1),
> > > DTS values for packets would be calculated incorrectly.
> > >
> > > Signed-off-by: tt2468 <tt2468 at irltoolkit.com>
> >
> > If you want to sign your commits off, please use a proper name.
> > A real name is not strictly required, but without it, a Sign-off becomes
> > a bit pointless.
> >
> > > ---
> > >   libavcodec/nvenc.c | 3 ++-
> > >   1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/libavcodec/nvenc.c b/libavcodec/nvenc.c
> > > index 9acf3e8697..8b02856507 100644
> > > --- a/libavcodec/nvenc.c
> > > +++ b/libavcodec/nvenc.c
> > > @@ -2266,7 +2266,8 @@ static int nvenc_set_timestamp(AVCodecContext
> *avctx,
> > >       dts = reorder_queue_dequeue(ctx->reorder_queue, avctx, pkt);
> > >
> > >       if (avctx->codec_descriptor->props & AV_CODEC_PROP_REORDER) {
> > > -        pkt->dts = dts - FFMAX(ctx->encode_config.frameIntervalP - 1,
> 0) * FFMAX(avctx->ticks_per_frame, 1);
> > > +        pkt->dts = dts -
> > > +            FFMAX(ctx->encode_config.frameIntervalP - 1, 0) *
> FFMAX(avctx->time_base.num * avctx->ticks_per_frame, avctx->time_base.num);
> >
> > What if the time_base is unset?
> > It's not really used anywhere else, so it might potentially never be set
> > by some users.
>
> time_base is a mandatory property on encoders. It is validated to be
> set on avcodec_open2. Of course if someone puts in some random values,
> thats on them.
>
> - Hendrik
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