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faster ff_sqrt()

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Originally committed as revision 859 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2002-08-22 19:41:39 +00:00
parent 1fb4890b51
commit f36db5dfd3
2 changed files with 12 additions and 1 deletions
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7
libavcodec/common.c
View File

@ -20,6 +20,13 @@
*/
#include "avcodec.h"
const UINT8 ff_sqrt_tab[128]={
0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,11
};
void init_put_bits(PutBitContext *s,
UINT8 *buffer, int buffer_size,
void *opaque,

6
libavcodec/common.h
View File

@ -901,6 +901,8 @@ static inline int clip(int a, int amin, int amax)
}
/* math */
extern const UINT8 ff_sqrt_tab[128];
int ff_gcd(int a, int b);
static inline int ff_sqrt(int a)
@ -908,7 +910,9 @@ static inline int ff_sqrt(int a)
int ret=0;
int s;
int ret_sq=0;
if(a<128) return ff_sqrt_tab[a];
for(s=15; s>=0; s--){
int b= ret_sq + (1<<(s*2)) + (ret<<s)*2;
if(b<=a){