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improved magnitude coding, 0.2% lower bitrate (foreman@352x288 qscale 1 and 8)

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Originally committed as revision 3372 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2004-08-02 17:53:57 +00:00
parent 9b434875f1
commit 0635cbfc32
1 changed files with 16 additions and 14 deletions
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30
libavcodec/snow.c
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@ -494,33 +494,35 @@ static inline int get_symbol(CABACContext *c, uint8_t *state, int is_signed){
static inline void put_symbol2(CABACContext *c, uint8_t *state, int v, int log2){
int i;
int e= av_log2(v<<1);
int r= log2>=0 ? 1<<log2 : 1;
assert(v>=0);
if(v==0) assert(e==0);
while(e > log2){
put_cabac(c, state+log2, 1);
v -= 1<<log2;
assert(v>=0);
e= av_log2(v<<1);
assert(log2>=-4);
while(v >= r){
put_cabac(c, state+4+log2, 1);
v -= r;
log2++;
if(log2>0) r+=r;
}
put_cabac(c, state+log2, 0);
put_cabac(c, state+4+log2, 0);
for(i=log2-1; i>=0; i--){
put_cabac(c, state+31-i, (v>>i)&1);
}
assert(!((v>>i)&1));
}
static inline int get_symbol2(CABACContext *c, uint8_t *state, int log2){
int i;
int r= log2>=0 ? 1<<log2 : 1;
int v=0;
while(get_cabac(c, state+log2)){
v+= 1<<log2;
assert(log2>=-4);
while(get_cabac(c, state+4+log2)){
v+= r;
log2++;
if(log2>0) r+=r;
}
for(i=log2-1; i>=0; i--){
@ -1839,7 +1841,7 @@ static void encode_subband_c0run(SnowContext *s, SubBand *b, DWTELEM *src, DWTEL
if(v){
int context= av_log2(/*ABS(ll) + */3*ABS(l) + ABS(lt) + 2*ABS(t) + ABS(rt) + ABS(p));
put_symbol(&s->c, b->state[context + 2], ABS(v)-1, 0);
put_symbol2(&s->c, b->state[context + 2], ABS(v)-1, context-4);
put_cabac(&s->c, &b->state[0][16 + 1 + 3 + quant3b[l&0xFF] + 3*quant3b[t&0xFF]], v<0);
}
}
@ -2255,7 +2257,7 @@ static inline void decode_subband(SnowContext *s, SubBand *b, DWTELEM *src, DWTE
}
if(v){
int context= av_log2(/*ABS(ll) + */3*ABS(l) + ABS(lt) + 2*ABS(t) + ABS(rt) + ABS(p));
v= get_symbol(&s->c, b->state[context + 2], 0) + 1;
v= get_symbol2(&s->c, b->state[context + 2], context-4) + 1;
if(get_cabac(&s->c, &b->state[0][16 + 1 + 3 + quant3b[l&0xFF] + 3*quant3b[t&0xFF]]))
v= -v;
src[x + y*stride]= v;