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/************************************************************************
*
* idctref.c, inverse DCT, double precision, for tmndecode (H.263 decoder)
* Copyright (C) 1995, 1996 Telenor R&D, Norway
*
* Contacts:
* Robert Danielsen <Robert.Danielsen@nta.no>
*
* 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 <mikeg@ee.ubc.ca>
* Guy Cote <guyc@ee.ubc.ca>
* Berna Erol <bernae@ee.ubc.ca>
*
* Contacts:
* Michael Gallant <mikeg@ee.ubc.ca>
*
* 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 <stefan@lis.e-technik.tu-muenchen.de>
*
*/
/* Perform IEEE 1180 reference (64-bit floating point, separable 8x1
* direct matrix multiply) Inverse Discrete Cosine Transform */
/* Here we use math.h to generate constants. Compiler results may vary a
* little */
#include <math.h>
#include "config.h"
#ifndef PI
# ifdef M_PI
# define PI M_PI
# else
# define PI 3.14159265358979323846
# endif
#endif
/* global declarations */
void init_idctref _ANSI_ARGS_ ((void));
void idctref _ANSI_ARGS_ ((short *block));
/* private data */
/* cosine transform matrix for 8x1 IDCT */
static double c[8][8];
/* initialize DCT coefficient matrix */
void init_idctref ()
{
int freq, time;
double scale;
for (freq = 0; freq < 8; freq++)
{
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));
}
}
/* perform IDCT matrix multiply for 8x8 coefficient block */
void idctref (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);
}
}
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