mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-23 15:53:08 +00:00
159 lines
3.9 KiB
C
159 lines
3.9 KiB
C
/**
|
|
* @file fdctref.c
|
|
* forward discrete cosine 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.
|
|
*
|
|
*/
|
|
|
|
#include <math.h>
|
|
|
|
#ifndef PI
|
|
# ifdef M_PI
|
|
# define PI M_PI
|
|
# else
|
|
# define PI 3.14159265358979323846
|
|
# endif
|
|
#endif
|
|
|
|
/* global declarations */
|
|
void init_fdct (void);
|
|
void fdct (short *block);
|
|
|
|
/* private data */
|
|
static double c[8][8]; /* transform coefficients */
|
|
|
|
void init_fdct()
|
|
{
|
|
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));
|
|
}
|
|
}
|
|
|
|
void fdct(block)
|
|
short *block;
|
|
{
|
|
register int i, j;
|
|
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];
|
|
*/
|
|
s += c[j][0] * block[8 * i + 0];
|
|
s += c[j][1] * block[8 * i + 1];
|
|
s += c[j][2] * block[8 * i + 2];
|
|
s += c[j][3] * block[8 * i + 3];
|
|
s += c[j][4] * block[8 * i + 4];
|
|
s += c[j][5] * block[8 * i + 5];
|
|
s += c[j][6] * block[8 * i + 6];
|
|
s += c[j][7] * block[8 * i + 7];
|
|
|
|
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];
|
|
*/
|
|
s += c[i][0] * tmp[8 * 0 + j];
|
|
s += c[i][1] * tmp[8 * 1 + j];
|
|
s += c[i][2] * tmp[8 * 2 + j];
|
|
s += c[i][3] * tmp[8 * 3 + j];
|
|
s += c[i][4] * tmp[8 * 4 + j];
|
|
s += c[i][5] * tmp[8 * 5 + j];
|
|
s += c[i][6] * tmp[8 * 6 + j];
|
|
s += c[i][7] * tmp[8 * 7 + j];
|
|
s*=8.0;
|
|
|
|
block[8 * i + j] = (short)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)
|
|
*/
|
|
}
|
|
}
|
|
|
|
/* perform IDCT matrix multiply for 8x8 coefficient block */
|
|
|
|
void 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;
|
|
}
|
|
}
|