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

[Hendrik Leppkes]

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