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optimize quantizaton (about 3x faster)

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further opt is easily possible but could lead to overflows depening upon coefficient range, so this wont be done yet as it would make the code somewhat less flexible

Originally committed as revision 3354 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2004-07-27 17:38:53 +00:00
parent a8d73e56e6
commit da66b6313e
1 changed files with 35 additions and 28 deletions
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63
libavcodec/snow.c
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@ -1801,29 +1801,33 @@ static void quantize(SnowContext *s, SubBand *b, DWTELEM *src, int stride, int b
const int h= b->height;
const int qlog= clip(s->qlog + b->qlog, 0, 128);
const int qmul= qexp[qlog&7]<<(qlog>>3);
int x,y;
int x,y, thres1, thres2;
START_TIMER
assert(QROOT==8);
bias= bias ? 0 : (3*qmul)>>3;
thres1= ((qmul - bias)>>QEXPSHIFT) - 1;
thres2= 2*thres1;
if(!bias){
for(y=0; y<h; y++){
for(x=0; x<w; x++){
int i= src[x + y*stride];
//FIXME use threshold
//FIXME optimize
//FIXME bias
if(i>=0){
i<<= QEXPSHIFT;
i/= qmul;
src[x + y*stride]= i;
}else{
i= -i;
i<<= QEXPSHIFT;
i/= qmul;
src[x + y*stride]= -i;
}
int i= src[x + y*stride];
if((unsigned)(i+thres1) > thres2){
if(i>=0){
i<<= QEXPSHIFT;
i/= qmul; //FIXME optimize
src[x + y*stride]= i;
}else{
i= -i;
i<<= QEXPSHIFT;
i/= qmul; //FIXME optimize
src[x + y*stride]= -i;
}
}else
src[x + y*stride]= 0;
}
}
}else{
@ -1831,22 +1835,25 @@ static void quantize(SnowContext *s, SubBand *b, DWTELEM *src, int stride, int b
for(x=0; x<w; x++){
int i= src[x + y*stride];
//FIXME use threshold
//FIXME optimize
//FIXME bias
if(i>=0){
i<<= QEXPSHIFT;
i= (i + bias) / qmul;
src[x + y*stride]= i;
}else{
i= -i;
i<<= QEXPSHIFT;
i= (i + bias) / qmul;
src[x + y*stride]= -i;
}
if((unsigned)(i+thres1) > thres2){
if(i>=0){
i<<= QEXPSHIFT;
i= (i + bias) / qmul; //FIXME optimize
src[x + y*stride]= i;
}else{
i= -i;
i<<= QEXPSHIFT;
i= (i + bias) / qmul; //FIXME optimize
src[x + y*stride]= -i;
}
}else
src[x + y*stride]= 0;
}
}
}
if(level+1 == s->spatial_decomposition_count){
// STOP_TIMER("quantize")
}
}
static void dequantize(SnowContext *s, SubBand *b, DWTELEM *src, int stride){