Hi all
spent a little bit of time fiddling around with quantize(). [I really
should be marking papers :/ ]
Sped the quantize routine up by about 15% on my p166/mmx. Just a fiddle
with pointers. Not sure if this will be a speedup across different cpus. Still
takes up far too much time though. The lame quantize routine takes more time
than the whole xing encoder. :(
Also, another speedup related to this one, but I'm out of programing
time: in count_bits(). Simply move the check for ix[i]>(8191+14) into the
quantize() routine. Save a bunch of seconds :) (see comment in code below)
The project is hurtling along!!
later
mike
-------------------
drop in quantize replacement
---------------------
void quantize( double xr[576], int ix[576], gr_info *cod_info )
{
register int b;
int j;
int i;
int *ixp;
double *xrp;
double quantizerStepSize; /* double step */
double istep_l,istep[3],temp;
static int init=0;
#define LUTABSIZE 10000
static int lutab[LUTABSIZE];
if (init==0) {
init++;
for (i=0;i<LUTABSIZE;i++) {
lutab[i]=nint(pow((double)i/10.0,0.75)-0.0946);
}
for (i=1;i<LUTABSIZE;i++)
if ((lutab[i]-lutab[i-1])==1) { /* we have a change over this interval
*/
lutab[i-1]=-1;
}
}
quantizerStepSize = cod_info->quantizerStepSize;
/* if subblock gain is used (short blocks), this should be: */
/* step = pow( 2.0, (quantizerStepSize - 8.0 * (double)
cod_info->subblock_gain[b]) * -0.25 ); */
/* step = pow( 2.0, quantizerStepSize * -0.25) *
pow( 2.0, 2*(double) cod_info->subblock_gain[b]) */
if ( quantizerStepSize == 0.0 )
istep_l = 1.0;
else
istep_l = pow ( 2.0, quantizerStepSize * -0.25 );
for (b=0;b<3;b++) {
if ((cod_info->block_type==2))
istep[b] = istep_l * pow(2.0,2* (double) cod_info->subblock_gain[b]);
else istep[b] = istep_l;
}
ixp = ix;
xrp = xr;
for (j=0;j<192;j++)
for (b=0;b<3;b++) {
temp=istep[b]*fabs(*xrp++); /* step always positive -> temp always
postive */
*ixp = 0;
if (temp<0.499996)
*ixp++;
else {
(*ixp)++;
if (temp<1.862955)
*ixp++;
else {
(*ixp)++;
if (temp<3.565282)
*ixp++;
else {
(*ixp)++;
if (temp<5.506396)
*ixp++;
else {
(*ixp)++;
if (temp<7.638304)
*ixp++;
else {
(*ixp)++;
if (temp<9.931741)
*ixp++;
else
if (temp<1000.0) {
*ixp = lutab[(int)(temp*10.0)];
if (*ixp < 0.0) /* too close to an interface, calculate
exact value */
*ixp++ = (int)( sqrt(sqrt(temp)*temp) + 0.4054);
else
*ixp++;
}
else
*ixp++ = (int)( sqrt(sqrt(temp)*temp) + 0.4054);
/*
Here is where you could put in the check for
ix[i]>8191+14 . (or temp > 139000)
and remove it from countbits. As soon as
this value was found, terminate quantize and
choose a new stepsize and start again. Which
is basically what the first part of countbits
does anyway */
}
}
}
}
}
}
}
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