163 lines
3.4 KiB
C++
163 lines
3.4 KiB
C++
#include "idct.h"
|
|
#define W1 2841 /* 2048*sqrt(2)*cos(1*pi/16) */
|
|
#define W2 2676 /* 2048*sqrt(2)*cos(2*pi/16) */
|
|
#define W3 2408 /* 2048*sqrt(2)*cos(3*pi/16) */
|
|
#define W5 1609 /* 2048*sqrt(2)*cos(5*pi/16) */
|
|
#define W6 1108 /* 2048*sqrt(2)*cos(6*pi/16) */
|
|
#define W7 565 /* 2048*sqrt(2)*cos(7*pi/16) */
|
|
|
|
|
|
short IDCT::iclip[1024];
|
|
short *IDCT::iclp=0;
|
|
bool IDCT::initted = false;
|
|
|
|
|
|
/* row (horizontal) IDCT
|
|
*
|
|
* 7 pi 1
|
|
* dst[k] = sum c[l] * src[l] * cos( -- * ( k + - ) * l )
|
|
* l=0 8 2
|
|
*
|
|
* where: c[0] = 128
|
|
* c[1..7] = 128*sqrt(2)
|
|
*/
|
|
|
|
void IDCT::idctrow(short *blk)
|
|
{
|
|
int x0, x1, x2, x3, x4, x5, x6, x7, x8;
|
|
|
|
/* shortcut */
|
|
if (!((x1 = blk[4]<<11) | (x2 = blk[6]) | (x3 = blk[2]) |
|
|
(x4 = blk[1]) | (x5 = blk[7]) | (x6 = blk[5]) | (x7 = blk[3])))
|
|
{
|
|
blk[0]=blk[1]=blk[2]=blk[3]=blk[4]=blk[5]=blk[6]=blk[7]=blk[0]<<3;
|
|
return;
|
|
}
|
|
|
|
x0 = (blk[0]<<11) + 128; /* for proper rounding in the fourth stage */
|
|
|
|
/* first stage */
|
|
x8 = W7*(x4+x5);
|
|
x4 = x8 + (W1-W7)*x4;
|
|
x5 = x8 - (W1+W7)*x5;
|
|
x8 = W3*(x6+x7);
|
|
x6 = x8 - (W3-W5)*x6;
|
|
x7 = x8 - (W3+W5)*x7;
|
|
|
|
/* second stage */
|
|
x8 = x0 + x1;
|
|
x0 -= x1;
|
|
x1 = W6*(x3+x2);
|
|
x2 = x1 - (W2+W6)*x2;
|
|
x3 = x1 + (W2-W6)*x3;
|
|
x1 = x4 + x6;
|
|
x4 -= x6;
|
|
x6 = x5 + x7;
|
|
x5 -= x7;
|
|
|
|
/* third stage */
|
|
x7 = x8 + x3;
|
|
x8 -= x3;
|
|
x3 = x0 + x2;
|
|
x0 -= x2;
|
|
x2 = (181*(x4+x5)+128)>>8;
|
|
x4 = (181*(x4-x5)+128)>>8;
|
|
|
|
/* fourth stage */
|
|
blk[0] = (x7+x1)>>8;
|
|
blk[1] = (x3+x2)>>8;
|
|
blk[2] = (x0+x4)>>8;
|
|
blk[3] = (x8+x6)>>8;
|
|
blk[4] = (x8-x6)>>8;
|
|
blk[5] = (x0-x4)>>8;
|
|
blk[6] = (x3-x2)>>8;
|
|
blk[7] = (x7-x1)>>8;
|
|
}
|
|
|
|
/* column (vertical) IDCT
|
|
*
|
|
* 7 pi 1
|
|
* dst[8*k] = sum c[l] * src[8*l] * cos( -- * ( k + - ) * l )
|
|
* l=0 8 2
|
|
*
|
|
* where: c[0] = 1/1024
|
|
* c[1..7] = (1/1024)*sqrt(2)
|
|
*/
|
|
void IDCT::idctcol(short *blk)
|
|
{
|
|
int x0, x1, x2, x3, x4, x5, x6, x7, x8;
|
|
|
|
/* shortcut */
|
|
if (!((x1 = (blk[8*4]<<8)) | (x2 = blk[8*6]) | (x3 = blk[8*2]) |
|
|
(x4 = blk[8*1]) | (x5 = blk[8*7]) | (x6 = blk[8*5]) | (x7 = blk[8*3])))
|
|
{
|
|
blk[8*0]=blk[8*1]=blk[8*2]=blk[8*3]=blk[8*4]=blk[8*5]=blk[8*6]=blk[8*7]=
|
|
iclp[(blk[8*0]+32)>>6];
|
|
return;
|
|
}
|
|
|
|
x0 = (blk[8*0]<<8) + 8192;
|
|
|
|
/* first stage */
|
|
x8 = W7*(x4+x5) + 4;
|
|
x4 = (x8+(W1-W7)*x4)>>3;
|
|
x5 = (x8-(W1+W7)*x5)>>3;
|
|
x8 = W3*(x6+x7) + 4;
|
|
x6 = (x8-(W3-W5)*x6)>>3;
|
|
x7 = (x8-(W3+W5)*x7)>>3;
|
|
|
|
/* second stage */
|
|
x8 = x0 + x1;
|
|
x0 -= x1;
|
|
x1 = W6*(x3+x2) + 4;
|
|
x2 = (x1-(W2+W6)*x2)>>3;
|
|
x3 = (x1+(W2-W6)*x3)>>3;
|
|
x1 = x4 + x6;
|
|
x4 -= x6;
|
|
x6 = x5 + x7;
|
|
x5 -= x7;
|
|
|
|
/* third stage */
|
|
x7 = x8 + x3;
|
|
x8 -= x3;
|
|
x3 = x0 + x2;
|
|
x0 -= x2;
|
|
x2 = (181*(x4+x5)+128)>>8;
|
|
x4 = (181*(x4-x5)+128)>>8;
|
|
|
|
/* fourth stage */
|
|
blk[8*0] = iclp[(x7+x1)>>14];
|
|
blk[8*1] = iclp[(x3+x2)>>14];
|
|
blk[8*2] = iclp[(x0+x4)>>14];
|
|
blk[8*3] = iclp[(x8+x6)>>14];
|
|
blk[8*4] = iclp[(x8-x6)>>14];
|
|
blk[8*5] = iclp[(x0-x4)>>14];
|
|
blk[8*6] = iclp[(x3-x2)>>14];
|
|
blk[8*7] = iclp[(x7-x1)>>14];
|
|
}
|
|
|
|
/* two dimensional inverse discrete cosine transform */
|
|
void IDCT::idct(short *block)
|
|
{
|
|
int i;
|
|
|
|
for (i=0; i<8; i++)
|
|
idctrow(block+8*i);
|
|
|
|
for (i=0; i<8; i++)
|
|
idctcol(block+i);
|
|
}
|
|
|
|
void IDCT::init()
|
|
{
|
|
if (!initted)
|
|
{
|
|
int i;
|
|
|
|
iclp = iclip+512;
|
|
for (i= -512; i<512; i++)
|
|
iclp[i] = (i<-256) ? -256 : ((i>255) ? 255 : i);
|
|
initted=true;
|
|
}
|
|
}
|