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avutil/rational: use frexp rather than ad-hoc log to get floating point exponent

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This simplifies and cleans up the code.
Furthermore, it is much faster due to absence of the slow log computation.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
This commit is contained in:
Ganesh Ajjanagadde 2015-10-29 00:18:15 -04:00
parent 865f6f410f
commit 8d9f86bd37
1 changed files with 2 additions and 2 deletions
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libavutil/rational.c
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@ -106,14 +106,14 @@ AVRational av_sub_q(AVRational b, AVRational c)
AVRational av_d2q(double d, int max)
{
AVRational a;
#define LOG2 0.69314718055994530941723212145817656807550013436025
int exponent;
int64_t den;
if (isnan(d))
return (AVRational) { 0,0 };
if (fabs(d) > INT_MAX + 3LL)
return (AVRational) { d < 0 ? -1 : 1, 0 };
exponent = FFMAX( (int)(log(fabs(d) + 1e-20)/LOG2), 0);
frexp(d, &exponent);
exponent = FFMAX(exponent-1, 0);
den = 1LL << (61 - exponent);
// (int64_t)rint() and llrint() do not work with gcc on ia64 and sparc64
av_reduce(&a.num, &a.den, floor(d * den + 0.5), den, max);