mirror of
https://gitlab.freedesktop.org/gstreamer/gstreamer.git
synced 2024-11-23 18:21:04 +00:00
102 lines
2.7 KiB
C
102 lines
2.7 KiB
C
/* 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>
|
|
|
|
#ifndef PI
|
|
# ifdef M_PI
|
|
# define PI M_PI
|
|
# else
|
|
# define PI 3.14159265358979323846
|
|
# endif
|
|
#endif
|
|
|
|
/* private data */
|
|
|
|
/* cosine transform matrix for 8x1 IDCT */
|
|
static double gst_idct_float_c[8][8];
|
|
|
|
/* initialize DCT coefficient matrix */
|
|
|
|
void gst_idct_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++)
|
|
gst_idct_float_c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5));
|
|
}
|
|
}
|
|
|
|
/* perform IDCT matrix multiply for 8x8 coefficient block */
|
|
|
|
void gst_idct_float_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+= gst_idct_float_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+= gst_idct_float_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);
|
|
}
|
|
}
|