www.pudn.com > encore50src.zip > text_dct.c
/**************************************************************************
* *
* This code is developed by Adam Li. This software is an *
* implementation of a part of one or more MPEG-4 Video tools as *
* specified in ISO/IEC 14496-2 standard. Those intending to use this *
* software module in hardware or software products are advised that its *
* use may infringe existing patents or copyrights, and any such use *
* would be at such party's own risk. The original developer of this *
* software module and his/her company, and subsequent editors and their *
* companies (including Project Mayo), will have no liability for use of *
* this software or modifications or derivatives thereof. *
* *
* Project Mayo gives users of the Codec a license to this software *
* module or modifications thereof for use in hardware or software *
* products claiming conformance to the MPEG-4 Video Standard as *
* described in the Open DivX license. *
* *
* The complete Open DivX license can be found at *
* http://www.projectmayo.com/opendivx/license.php . *
* *
**************************************************************************/
/**************************************************************************
*
* text_dct.c
*
* Copyright (C) 2001 Project Mayo
*
* Adam Li
*
* DivX Advance Research Center
*
**************************************************************************/
/* This file contains some functions for fDCT/iDCT transformation. */
/* Some codes of this project come from SSG MPEG-2 implementation. */
/* Please see seperate acknowledgement file for a list of contributors. */
#include
/* The first part of it is for the forward DCT */
#ifndef PI
# ifdef M_PI
# define PI M_PI
# else
# define PI 3.14159265358979323846
# endif
#endif
/* private data */
static double c[8][8]; /* transform coefficients */
void fdct_enc(block)
short *block;
{
int i, j, k;
double s;
double tmp[64];
for (i=0; i<8; i++)
for (j=0; j<8; j++)
{
s = 0.0;
for (k=0; k<8; k++)
s += c[j][k] * block[8*i+k];
tmp[8*i+j] = s;
}
for (j=0; j<8; j++)
for (i=0; i<8; i++)
{
s = 0.0;
for (k=0; k<8; k++)
s += c[i][k] * tmp[8*k+j];
block[8*i+j] = (int)floor(s+0.499999);
/*
* reason for adding 0.499999 instead of 0.5:
* s is quite often x.5 (at least for i and/or j = 0 or 4)
* and setting the rounding threshold exactly to 0.5 leads to an
* extremely high arithmetic implementation dependency of the result;
* s being between x.5 and x.500001 (which is now incorrectly rounded
* downwards instead of upwards) is assumed to occur less often
* (if at all)
*/
}
}
void init_fdct_enc()
{
int i, j;
double s;
for (i=0; i<8; i++)
{
s = (i==0) ? sqrt(0.125) : 0.5;
for (j=0; j<8; j++)
c[i][j] = s * cos((PI/8.0)*i*(j+0.5));
}
}
/* the second part of it is for the inverse DCT */
#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) */
/* private data */
static short iclip[1024]; /* clipping table */
static short *iclp;
/* private prototypes */
static void idctrow_enc (short *blk);
static void idctcol_enc (short *blk);
/* two dimensional inverse discrete cosine transform */
void idct_enc(block)
short *block;
{
int i;
for (i=0; i<8; i++)
idctrow_enc(block+8*i);
for (i=0; i<8; i++)
idctcol_enc(block+i);
}
void init_idct_enc()
{
int i;
iclp = iclip+512;
for (i= -512; i<512; i++)
iclp[i] = (i<-256) ? -256 : ((i>255) ? 255 : i);
}
/* 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)
*/
static void idctrow_enc(blk)
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)
*/
static void idctcol_enc(blk)
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];
}