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avutil/mathematics: add av_add_stable()

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Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2014-01-03 17:30:50 +01:00
parent de5b6c736b
commit b317f9459f
4 changed files with 32 additions and 1 deletions
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3
doc/APIchanges
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@ -15,6 +15,9 @@ libavutil: 2012-10-22
API changes, most recent first:
2014-01-04 - xxxxxxx - lavu 52.60.100 - mathematics.h
Add av_add_stable() function.
2013-12-22 - xxxxxxx - lavu 52.59.100 - avstring.h
Add av_strnlen() function.

14
libavutil/mathematics.c
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@ -174,3 +174,17 @@ simple_round:
return av_rescale_q(this, fs_tb, out_tb);
}
int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc)
{
AVRational step = av_mul_q(inc_tb, (AVRational) {inc, 1});
if (av_cmp_q(step, ts_tb) < 0) {
//increase step is too small for even 1 step to be representable
return ts;
} else {
int64_t old = av_rescale_q(ts, ts_tb, step);
int64_t old_ts = av_rescale_q(old, step, ts_tb);
return av_rescale_q(old + 1, step, ts_tb) + (ts - old_ts);
}
}

14
libavutil/mathematics.h
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@ -141,6 +141,20 @@ int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod);
int64_t av_rescale_delta(AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb);
/**
* Add a value to a timestamp.
*
* This function gurantees that when the same value is repeatly added that
* no accumulation of rounding errors occurs.
*
* @param ts Input timestamp
* @param ts_tb Input timestamp timebase
* @param inc value to add to ts
* @param inc_tb inc timebase
*/
int64_t av_add_stable(AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc);
/**
* @}
*/

2
libavutil/version.h
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@ -56,7 +56,7 @@
*/
#define LIBAVUTIL_VERSION_MAJOR 52
#define LIBAVUTIL_VERSION_MINOR 59
#define LIBAVUTIL_VERSION_MINOR 60
#define LIBAVUTIL_VERSION_MICRO 100
#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \