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tweak cabac. 0.5% faster h264.

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Originally committed as revision 6106 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Loren Merritt 2006-08-27 09:19:02 +00:00
parent 39b434c6ae
commit bfe328caf0
1 changed files with 12 additions and 10 deletions
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22
libavcodec/cabac.h
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@ -295,28 +295,30 @@ static inline void renorm_cabac_decoder(CABACContext *c){
}
static inline void renorm_cabac_decoder_once(CABACContext *c){
int mask= (c->range - (0x200 << CABAC_BITS))>>31;
c->range+= c->range&mask;
c->low += c->low &mask;
int shift= (uint32_t)(c->range - (0x200 << CABAC_BITS))>>31;
c->range<<= shift;
c->low <<= shift;
if(!(c->low & CABAC_MASK))
refill(c);
}
static inline int get_cabac(CABACContext *c, uint8_t * const state){
int RangeLPS= c->lps_range[*state][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);
//FIXME gcc generates duplicate load/stores for c->low and c->range
int s = *state;
int RangeLPS= c->lps_range[s][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);
int bit, lps_mask attribute_unused;
c->range -= RangeLPS;
#if 1
if(c->low < c->range){
bit= (*state)&1;
*state= c->mps_state[*state];
bit= s&1;
*state= c->mps_state[s];
renorm_cabac_decoder_once(c);
}else{
// int shift= ff_h264_norm_shift[RangeLPS>>17];
bit= ((*state)&1)^1;
bit= (s&1)^1;
c->low -= c->range;
*state= c->lps_state[*state];
*state= c->lps_state[s];
c->range = RangeLPS;
renorm_cabac_decoder(c);
/* c->range = RangeLPS<<shift;
@ -331,8 +333,8 @@ static inline int get_cabac(CABACContext *c, uint8_t * const state){
c->low -= c->range & lps_mask;
c->range += (RangeLPS - c->range) & lps_mask;
bit= ((*state)^lps_mask)&1;
*state= c->mps_state[(*state) - (128&lps_mask)];
bit= (s^lps_mask)&1;
*state= c->mps_state[s - (128&lps_mask)];
lps_mask= ff_h264_norm_shift[c->range>>(CABAC_BITS+2)];
c->range<<= lps_mask;