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

[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.
  *
-- 
2.17.1