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Provide direct implementations ec_{enc|dec}_bit_prob() that do not require a division instead of using the normal entropy coder path. This should be exactly equivalent to the existing code.

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Timothy B. Terriberry 2010-05-29 22:47:37 -04:00 • committed by Jean-Marc Valin
parent 8cc945c53a
commit 299747ee24
5 changed files with 31 additions and 32 deletions
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18
libcelt/entdec.c
View file

@ -111,21 +111,3 @@ ec_uint32 ec_dec_uint(ec_dec *_this,ec_uint32 _ft){
return t;
}
}
/* The probability of having a "one" is given in 1/256 */
int ec_dec_bit_prob(ec_dec *_this,int _prob)
{
int val;
int fl=0, fh=256-_prob;
val = ec_decode_bin(_this, 8);
if (val >= fh)
{
val = 1;
fl=fh;
fh=256;
} else {
val = 0;
}
ec_dec_update(_this,fl,fh,256);
return val;
}

3
libcelt/entdec.h
View file

@ -47,8 +47,7 @@ struct ec_dec{
int rem;
/*The number of values in the current range.*/
ec_uint32 rng;
/*The difference between the input value and the lowest value in the current
range.*/
/*The difference between the top of the current range and the input value.*/
ec_uint32 dif;
/*Normalization factor.*/
ec_uint32 nrm;

12
libcelt/entenc.c
View file

@ -100,15 +100,3 @@ void ec_enc_uint(ec_enc *_this,ec_uint32 _fl,ec_uint32 _ft){
ec_encode(_this,_fl,_fl+1,_ft+1);
}
}
/* The probability of having a "one" is given in 1/256 */
void ec_enc_bit_prob(ec_enc *_this,int val,int _prob)
{
int fl=0, fh=256-_prob;
if (val)
{
fl=fh;
fh=256;
}
ec_encode_bin(_this,fl,fh,8);
}

16
libcelt/rangedec.c
View file

@ -186,6 +186,22 @@ void ec_dec_update(ec_dec *_this,unsigned _fl,unsigned _fh,unsigned _ft){
ec_dec_normalize(_this);
}
/*The probability of having a "one" is given in 1/256.*/
int ec_dec_bit_prob(ec_dec *_this,int _prob){
ec_uint32 r;
ec_uint32 s;
ec_uint32 d;
int val;
r=_this->rng;
d=_this->dif;
s=IMUL32(r>>8,_prob);
val=d<=s;
if(!val)_this->dif=d-s;
_this->rng=val?s:r-s;
ec_dec_normalize(_this);
return val;
}
long ec_dec_tell(ec_dec *_this,int _b){
ec_uint32 r;
int l;

14
libcelt/rangeenc.c
View file

@ -138,6 +138,20 @@ void ec_encode_bin(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned _bits){
ec_enc_normalize(_this);
}
/*The probability of having a "one" is given in 1/256.*/
void ec_enc_bit_prob(ec_enc *_this,int _val,int _prob){
ec_uint32 r;
ec_uint32 s;
ec_uint32 l;
r=_this->rng;
l=_this->low;
s=IMUL32(r>>8,_prob);
r-=s;
if(_val)_this->low=l+r;
_this->rng=_val?s:r;
ec_enc_normalize(_this);
}
void ec_encode_raw(ec_enc *_this,unsigned _fl,unsigned _fh,unsigned bits){
_this->nb_end_bits += bits;
while (bits >= _this->end_bits_left)