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adx: use 12-bit coefficients instead of 14-bit to avoid integer overflow

This commit is contained in:
Justin Ruggles 2011-11-20 14:03:21 -05:00
parent c52ddc6024
commit 954d94dd5e
3 changed files with 5 additions and 5 deletions
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6
libavcodec/adx.h
View File

@ -43,8 +43,8 @@ typedef struct {
int in_temp;
} ADXContext;
#define BASEVOL 0x4000
#define SCALE1 0x7298
#define SCALE2 0x3350
#define COEFF_BITS 12
#define COEFF1 0x1CA6
#define COEFF2 0x0CD4
#endif /* AVCODEC_ADX_H */

2
libavcodec/adxdec.c
View File

@ -59,7 +59,7 @@ static void adx_decode(ADXContext *c, int16_t *out, const uint8_t *in, int ch)
s2 = prev->s2;
for (i = 0; i < 32; i++) {
d = get_sbits(&gb, 4);
s0 = (BASEVOL * d * scale + SCALE1 * s1 - SCALE2 * s2) >> 14;
s0 = ((d << COEFF_BITS) * scale + COEFF1 * s1 - COEFF2 * s2) >> COEFF_BITS;
s2 = s1;
s1 = av_clip_int16(s0);
*out = s1;

2
libavcodec/adxenc.c
View File

@ -48,7 +48,7 @@ static void adx_encode(unsigned char *adx,const short *wav,
s2 = prev->s2;
for(i=0;i<32;i++) {
s0 = wav[i];
d = ((s0<<14) - SCALE1*s1 + SCALE2*s2)/BASEVOL;
d = ((s0 << COEFF_BITS) - COEFF1 * s1 + COEFF2 * s2) >> COEFF_BITS;
data[i]=d;
if (max<d) max=d;
if (min>d) min=d;