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Implement av_nearer_q() and av_find_nearest_q_idx() functions.

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Originally committed as revision 15415 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Stefano Sabatini
2008-09-25 19:23:13 +00:00
parent 5f129a05bf
commit 05b90fc0c5
3 changed files with 39 additions and 1 deletions
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25
libavutil/rational.c
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@@ -101,3 +101,28 @@ AVRational av_d2q(double d, int max){
return a;
}
int av_nearer_q(AVRational q, AVRational q1, AVRational q2)
{
/* n/d is q, a/b is the median between q1 and q2 */
int64_t a = q1.num * (int64_t)q2.den + q2.num * (int64_t)q1.den;
int64_t b = 2 * (int64_t)q1.den * q2.den;
/* rnd_up(a*d/b) > n => a*d/b > n */
int64_t x_up = av_rescale_rnd(a, q.den, b, AV_ROUND_UP);
/* rnd_down(a*d/b) < n => a*d/b < n */
int64_t x_down = av_rescale_rnd(a, q.den, b, AV_ROUND_DOWN);
return ((x_up > q.num) - (x_down < q.num)) * av_cmp_q(q2, q1);
}
int av_find_nearest_q_idx(AVRational q, const AVRational* q_list)
{
int i, nearest_q_idx = 0;
for(i=0; q_list[i].den; i++)
if (av_nearer_q(q, q_list[i], q_list[nearest_q_idx]) > 0)
nearest_q_idx = i;
return nearest_q_idx;
}