Re: [FFmpeg-devel] [PATCH v2 4/7] avutil/mathematics: add av_rescale_interval() function

[Pierre-Anthony Lemieux <pal@sandflow.com>]

On Fri, Mar 4, 2022 at 12:13 PM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> pal@sandflow.com:
> > From: Pierre-Anthony Lemieux <pal@palemieux.com>
> >
> > Refactors a function used by avformat/concat and avformat/imf.
> >
> > ---
> >  libavutil/mathematics.c | 10 ++++++++++
> >  libavutil/mathematics.h | 21 +++++++++++++++++++++
> >  2 files changed, 31 insertions(+)
> >
> > diff --git a/libavutil/mathematics.c b/libavutil/mathematics.c
> > index f4e541fa24..2c7f57b950 100644
> > --- a/libavutil/mathematics.c
> > +++ b/libavutil/mathematics.c
> > @@ -212,3 +212,13 @@ int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t i
> >          return av_sat_add64(av_rescale_q(old + 1, inc_tb, ts_tb), ts - old_ts);
> >      }
> >  }
> > +
> > +void av_rescale_interval(AVRational tb_in, AVRational tb_out,
> > +                         int64_t *min_ts, int64_t *ts, int64_t *max_ts)
> > +{
> > +    *ts     = av_rescale_q    (*    ts, tb_in, tb_out);
> > +    *min_ts = av_rescale_q_rnd(*min_ts, tb_in, tb_out,
> > +                               AV_ROUND_UP   | AV_ROUND_PASS_MINMAX);
> > +    *max_ts = av_rescale_q_rnd(*max_ts, tb_in, tb_out,
> > +                               AV_ROUND_DOWN | AV_ROUND_PASS_MINMAX);
> > +}
> > diff --git a/libavutil/mathematics.h b/libavutil/mathematics.h
> > index 64d4137a60..eb8a3f4002 100644
> > --- a/libavutil/mathematics.h
> > +++ b/libavutil/mathematics.h
> > @@ -161,6 +161,27 @@ int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;
> >  int64_t av_rescale_q_rnd(int64_t a, AVRational bq, AVRational cq,
> >                           enum AVRounding rnd) av_const;
> >
> > +/**
> > + * Rescales a timestamp and the endpoints of an interval to which the temstamp
> > + * belongs, from a timebase `tb_in` to a timebase `tb_out`.
> > + *
> > + * The upper (lower) bound of the output interval is rounded up (down) such that
> > + * the output interval always falls within the intput interval. The timestamp is
> > + * rounded to the nearest integer and halfway cases away from zero, and can
> > + * therefore fall outside of the output interval.
> > + *
> > + * Useful to simplify the rescaling of the arguments of AVInputFormat::read_seek2()
> > + *
> > + * @param[in] tb_in      Timebase of the input `min_ts`, `ts` and `max_ts`
> > + * @param[in] tb_out     Timebase of the ouput `min_ts`, `ts` and `max_ts`
> > + * @param[in,out] min_ts Lower bound of the interval
> > + * @param[in,out] ts     Timestamp
> > + * @param[in,out] max_ts Upper bound of the interval
> > + */
> > +void av_rescale_interval(AVRational tb_in, AVRational tb_out,
> > +                         int64_t *min_ts, int64_t *ts, int64_t *max_ts);
> > +
> > +
> >  /**
> >   * Compare two timestamps each in its own time base.
> >   *
>
> I don't see why this function should be public at all. It seems very
> specific to a usecase in lavf.

Ok. Unless someone objects/has a better idea, I cam move it to seek.c
as ff_rescale_interval() since it is primarily useful (today) with
seek_file().

>
> - Andreas
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