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/* Reference_IDCT.c, Inverse Discrete Fourier Transform, double precision */
/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */
/*
* Disclaimer of Warranty
*
* These software programs are available to the user without any license fee or
* royalty on an "as is" basis. The MPEG Software Simulation Group 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 MPEG Software Simulation Group does not represent or warrant that the
* programs furnished hereunder are free of infringement of any third-party
* patents.
*
* Commercial implementations of MPEG-1 and MPEG-2 video, 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.
*
*/
/* 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 Initialize_Fast_IDCTref _ANSI_ARGS_
((void));
void Reference_IDCT _ANSI_ARGS_
((short *block
));
/* private data */
/* cosine transform matrix for 8x1 IDCT */
static double c
[8][8];
/* initialize DCT coefficient matrix */
void Initialize_Reference_IDCT
()
{
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 Reference_IDCT
(block
)
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
);
}
}