Hi all,
The patch included in this mail speeds up old filter_subband(), and It
seems that same speed-up can be applied to current window_subband(). I
tried to understand how current window_subband() works, but I couldn't.
Someone, please explain it.
Naoki
*** filterbank.c~ Mon Nov 8 10:58:50 1999
--- filterbank.c Sat Apr 29 13:23:56 2000
***************
*** 208,213 ****
--- 208,305 ----
************************************************************************/
+ void idct32(double a[])
+ {
+ /* returns sum_j=0^31 a[j]*cos(PI*j*(k+1/2)/32), 0<=k<32 */
+
+ static double costab[] = {
+ 0.5006029982351962726 ,0.74453627100229857749,0.5531038960344445421
+,1.4841646163141661852,
+
+0.51544730992262455249,0.97256823786196078263,0.62250412303566482475,3.4076084184687189804,
+
+0.50547095989754364798,0.83934964541552681272,0.58293496820613388554,2.0577810099534108446,
+ 0.53104259108978413284,1.1694399334328846596 ,0.674808341455005678
+,10.19000812354803287 ,
+ 0.5024192861881556782
+,0.78815462345125020249,0.56694403481635768927,1.7224470982383341955,
+ 0.52249861493968885462,1.0606776859903470633
+,0.64682178335999007679,5.1011486186891552563,
+
+0.50979557910415917998,0.89997622313641556513,0.60134488693504528634,2.5629154477415054814,
+ 0.54119610014619701222,1.3065629648763763537 ,0.70710678118654746172,
+ };
+
+ static unsigned char addtab[] = {
+ 1,29,31, 2, 1,25,27, 2, 1,21,23, 2, 1,17,19, 2,
+ 1,13,15, 2, 1, 9,11, 2, 1, 5, 7, 2, 0, 3, 1,
+ 1,27,31, 4, 1,26,30, 4, 1,19,23, 4, 1,18,22, 4,
+ 1,11,15, 4, 1,10,14, 4, 0, 7, 3, 0, 6, 2,
+ 1,23,31, 8, 1,22,30, 8, 1,21,29, 8, 1,20,28, 8,
+ 0,15, 7, 0,14, 6, 0,13, 5, 0,12, 4,
+ 0,31,15, 0,30,14, 0,29,13, 0,28,12,
+ 0,27,11, 0,26,10, 0,25, 9, 0,24, 8,
+ };
+
+ static unsigned char buttab[] = {
+ 15,31,30, 14,30,30, 13,29,30, 12,28,30,
+ 11,27,30, 10,26,30, 9,25,30, 8,24,30,
+ 7,23,30, 6,22,30, 5,21,30, 4,20,30,
+ 3,19,30, 2,18,30, 1,17,30, 0,16,30,
+ 23,15,29, 22,14,29, 21,13,29, 20,12,29,
+ 19,11,29, 18,10,29, 17, 9,29, 16, 8,29,
+ 7,31,28, 6,30,28, 5,29,28, 4,28,28,
+ 3,27,28, 2,26,28, 1,25,28, 0,24,28,
+ 27, 7,27, 26, 6,27, 25, 5,27, 24, 4,27,
+ 19,15,26, 18,14,26, 17,13,26, 16,12,26,
+ 11,23,25, 10,22,25, 9,21,25, 8,20,25,
+ 3,31,24, 2,30,24, 1,29,24, 0,28,24,
+ 29, 3,23, 28, 2,23, 25, 7,22, 24, 6,22,
+ 21,11,21, 20,10,21, 17,15,20, 16,14,20,
+ 13,19,19, 12,18,19, 9,23,18, 8,22,18,
+ 5,27,17, 4,26,17, 1,31,16, 0,30,16,
+ 30, 1,15, 28, 3,14, 26, 5,13, 24, 7,12,
+ 22, 9,11, 20,11,10, 18,13, 9, 16,15, 8,
+ 14,17, 7, 12,19, 6, 10,21, 5, 8,23, 4,
+ 6,25, 3, 4,27, 2, 2,29, 1, 0,31, 0,
+ };
+
+ static unsigned char swaptab[] = {
+ 1,16, 2, 8, 3,24, 5,20,
+ 6,12, 7,28, 9,18, 11,26,
+ 13,22, 15,30, 19,25, 23,29,
+ };
+
+ int i;
+ unsigned char *p;
+
+ p = addtab;
+ for(i=0;i<32;i++)
+ {
+ if (p[0]) {
+ a[p[2]] = -a[p[2]] - a[p[1]];
+ a[p[1]] += a[p[1] - p[3]];
+ p += 4;
+ } else {
+ a[p[1]] = -a[p[1]] - a[p[2]];
+ p += 3;
+ }
+ }
+
+ p = buttab;
+ for(i=0;i<80;i++)
+ {
+ double xr;
+ xr = a[p[1]]*costab[p[2]];
+ a[p[1]] = (a[p[0]] - xr);
+ a[p[0]] = (a[p[0]] + xr);
+ p += 3;
+ }
+
+ p = swaptab;
+ for(i=0;i<12;i++)
+ {
+ double xr;
+ xr = a[p[0]];
+ a[p[0]] = a[p[1]];
+ a[p[1]] = xr;
+ p += 2;
+ }
+ }
+
void filter_subband(double z[64], double s[SBLIMIT]) {
double yprime[32];
***************
*** 217,222 ****
--- 309,315 ----
double s0,s1;
+ #if 0
if(!init) {
init=1;
for (i=0; i<16; i++) for (j=0; j<32; j++)
***************
*** 240,245 ****
--- 333,349 ----
s[31-i] = s0-s1;
}
+ #else
+ s[0] = z[16];
+
+ for(i=1;i<=16;i++)
+ s[i] = z[i+16]+z[16-i];
+
+ for(i=17;i<=31;i++)
+ s[i] = z[i+16]-z[80-i];
+
+ idct32(s);
+ #endif
}
--
Naoki Shibata e-mail: [EMAIL PROTECTED]
--
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