www.pudn.com > MPEG4Codec.zip > IDCT.C
/************************************************************************
*
* idct.c, inverse fast DCT for tmndecode (H.263 decoder)
* Copyright (C) 1995, 1996 Telenor R&D, Norway
*
* Contacts:
* Robert Danielsen
*
* Telenor Research and Development http://www.nta.no/brukere/DVC/
* P.O.Box 83 tel.: +47 63 84 84 00
* N-2007 Kjeller, Norway fax.: +47 63 81 00 76
*
* Copyright (C) 1997 University of BC, Canada
* Modified by: Michael Gallant
* Guy Cote
* Berna Erol
*
* Contacts:
* Michael Gallant
*
* UBC Image Processing Laboratory http://www.ee.ubc.ca/image
* 2356 Main Mall tel.: +1 604 822 4051
* Vancouver BC Canada V6T1Z4 fax.: +1 604 822 5949
*
************************************************************************/
/* Disclaimer of Warranty
*
* These software programs are available to the user without any license fee
* or royalty on an "as is" basis. The University of British Columbia
* disclaims any and all warranties, whether express, implied, or
* statuary, including any implied warranties or merchantability or of
* fitness for a particular purpose. In no event shall the
* copyright-holder be liable for any incidental, punitive, or
* consequential damages of any kind whatsoever arising from the use of
* these programs.
*
* This disclaimer of warranty extends to the user of these programs and
* user's customers, employees, agents, transferees, successors, and
* assigns.
*
* The University of British Columbia does not represent or warrant that the
* programs furnished hereunder are free of infringement of any
* third-party patents.
*
* Commercial implementations of H.263, including shareware, are subject to
* royalty fees to patent holders. Many of these patents are general
* enough such that they are unavoidable regardless of implementation
* design.
*
*/
/* based on mpeg2decode, (C) 1994, MPEG Software Simulation Group and
* mpeg2play, (C) 1994 Stefan Eckart
*
*/
/**********************************************************/
/* inverse two dimensional DCT, Chen-Wang algorithm */
/* (cf. IEEE ASSP-32, pp. 803-816, Aug. 1984) */
/* 32-bit integer arithmetic (8 bit coefficients) */
/* 11 mults, 29 adds per DCT */
/* sE, 18.8.91 */
/**********************************************************/
/* coefficients extended to 12 bit for IEEE1180-1990 */
/* compliance sE, 2.1.94 */
/**********************************************************/
/* this code assumes >> to be a two's-complement arithmetic */
/* right shift: (-2)>>1 == -1 , (-3)>>1 == -2 */
#include "mp4_vars.h"
void init_idct ();
#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) */
/* 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 (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 (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] =
mp4_state->clp[(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] = mp4_state->clp[(x7 + x1) >> 14];
blk[8 * 1] = mp4_state->clp[(x3 + x2) >> 14];
blk[8 * 2] = mp4_state->clp[(x0 + x4) >> 14];
blk[8 * 3] = mp4_state->clp[(x8 + x6) >> 14];
blk[8 * 4] = mp4_state->clp[(x8 - x6) >> 14];
blk[8 * 5] = mp4_state->clp[(x0 - x4) >> 14];
blk[8 * 6] = mp4_state->clp[(x3 - x2) >> 14];
blk[8 * 7] = mp4_state->clp[(x7 - x1) >> 14];
}
/*
two dimensional inverse discrete cosine transform
this is a reference implementation - no speed optimized
*/
void idct (short *block)
{
int i;
for (i = 0; i < 8; i++)
idctrow (block + 8 * i);
for (i = 0; i < 8; i++)
idctcol (block + i);
}