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/* idctref.c, Inverse Discrete Fourier Transform, double precision */
/* Copyright (C) 1994, 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>
#ifndef __STDC__
#define _ANSI_ARGS_(x) ()
#else
#define _ANSI_ARGS_(x) x
#endif
#define RB "rb"
#define WB "wb"
#ifndef O_BINARY
#define O_BINARY 0
#endif
#ifndef PI
# ifdef M_PI
# define PI M_PI
# else
# define PI 3.14159265358979323846
# endif
#endif
/* global declarations */
void init_float_idct _ANSI_ARGS_((void));
void float_idct _ANSI_ARGS_((short *block));
/* private data */
/* cosine transform matrix for 8x1 IDCT */
static double c[8][8];
/* initialize DCT coefficient matrix */
void init_float_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 float_idct( 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);
}
}
/* EOF */
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