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swresample/resample: merge first iteration into init in bessel() 

speedup of about 1%

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2015-10-07 17:33:00 +02:00
parent 322e960dbf
commit 6024c865ef
1 changed files with 4 additions and 3 deletions
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7
libswresample/resample.c
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@ -32,9 +32,8 @@
* 0th order modified bessel function of the first kind.
*/
static double bessel(double x){
double v=1;
double lastv=0;
double t=1;
double t, v;
int i;
static const double inv[100]={
1.0/( 1* 1), 1.0/( 2* 2), 1.0/( 3* 3), 1.0/( 4* 4), 1.0/( 5* 5), 1.0/( 6* 6), 1.0/( 7* 7), 1.0/( 8* 8), 1.0/( 9* 9), 1.0/(10*10),
@ -50,7 +49,9 @@ static double bessel(double x){
};
x= x*x/4;
for(i=0; v != lastv; i++){
t = x;
v = 1 + x;
for(i=1; v != lastv; i++){
lastv=v;
t *= x*inv[i];
v += t;