mirror of
https://github.com/WinampDesktop/winamp.git
synced 2024-12-03 17:07:16 +01:00
67 lines
1.2 KiB
C++
67 lines
1.2 KiB
C++
#include "idctref.h"
|
|
#include <math.h>
|
|
#ifndef PI
|
|
# ifdef M_PI
|
|
# define PI M_PI
|
|
# else
|
|
# define PI 3.14159265358979323846
|
|
# endif
|
|
#endif
|
|
|
|
bool IDCTRef::initted = false;
|
|
double IDCTRef::c[8][8]; /* cosine transform matrix for 8x1 IDCT */
|
|
|
|
|
|
/* initialize DCT coefficient matrix */
|
|
|
|
void IDCTRef::init()
|
|
{
|
|
if (!initted)
|
|
{
|
|
int freq, time;
|
|
|
|
for (freq=0; freq < 8; freq++)
|
|
{
|
|
double scale = (freq == 0) ? sqrt(0.125) : 0.5;
|
|
for (time=0; time<8; time++)
|
|
c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5));
|
|
}
|
|
initted=true;
|
|
}
|
|
}
|
|
|
|
/* perform IDCT matrix multiply for 8x8 coefficient block */
|
|
|
|
void IDCTRef::idct(short *block)
|
|
{
|
|
int i, j, k, v;
|
|
double partial_product;
|
|
double tmp[64];
|
|
|
|
for (i=0; i<8; i++)
|
|
for (j=0; j<8; j++)
|
|
{
|
|
partial_product = 0.0;
|
|
|
|
for (k=0; k<8; k++)
|
|
partial_product+= c[k][j]*block[8*i+k];
|
|
|
|
tmp[8*i+j] = partial_product;
|
|
}
|
|
|
|
/* Transpose operation is integrated into address mapping by switching
|
|
loop order of i and j */
|
|
|
|
for (j=0; j<8; j++)
|
|
for (i=0; i<8; i++)
|
|
{
|
|
partial_product = 0.0;
|
|
|
|
for (k=0; k<8; k++)
|
|
partial_product+= c[k][i]*tmp[8*k+j];
|
|
|
|
v = (int)floor(partial_product+0.5);
|
|
block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v);
|
|
}
|
|
}
|