/************************************************************************** * * * 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]; }