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

[Andreas Rheinhardt]

pal at sandflow.com:
> From: Pierre-Anthony Lemieux <pal at 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.

- Andreas