mirror of
https://github.com/pineappleEA/pineapple-src.git
synced 2024-11-25 13:18:24 -05:00
124 lines
3.4 KiB
C
Executable File
124 lines
3.4 KiB
C
Executable File
/*
|
|
* reference discrete cosine transform (double precision)
|
|
* Copyright (C) 2009 Dylan Yudaken
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* reference discrete cosine transform (double precision)
|
|
*
|
|
* @author Dylan Yudaken (dyudaken at gmail)
|
|
*
|
|
* @note This file could be optimized a lot, but is for
|
|
* reference and so readability is better.
|
|
*/
|
|
|
|
#include "libavutil/mathematics.h"
|
|
#include "dctref.h"
|
|
|
|
static double coefficients[8 * 8];
|
|
|
|
/**
|
|
* Initialize the double precision discrete cosine transform
|
|
* functions fdct & idct.
|
|
*/
|
|
av_cold void ff_ref_dct_init(void)
|
|
{
|
|
unsigned int i, j;
|
|
|
|
for (j = 0; j < 8; ++j) {
|
|
coefficients[j] = sqrt(0.125);
|
|
for (i = 8; i < 64; i += 8) {
|
|
coefficients[i + j] = 0.5 * cos(i * (j + 0.5) * M_PI / 64.0);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Transform 8x8 block of data with a double precision forward DCT <br>
|
|
* This is a reference implementation.
|
|
*
|
|
* @param block pointer to 8x8 block of data to transform
|
|
*/
|
|
void ff_ref_fdct(short *block)
|
|
{
|
|
/* implement the equation: block = coefficients * block * coefficients' */
|
|
|
|
unsigned int i, j, k;
|
|
double out[8 * 8];
|
|
|
|
/* out = coefficients * block */
|
|
for (i = 0; i < 64; i += 8) {
|
|
for (j = 0; j < 8; ++j) {
|
|
double tmp = 0;
|
|
for (k = 0; k < 8; ++k) {
|
|
tmp += coefficients[i + k] * block[k * 8 + j];
|
|
}
|
|
out[i + j] = tmp * 8;
|
|
}
|
|
}
|
|
|
|
/* block = out * (coefficients') */
|
|
for (j = 0; j < 8; ++j) {
|
|
for (i = 0; i < 64; i += 8) {
|
|
double tmp = 0;
|
|
for (k = 0; k < 8; ++k) {
|
|
tmp += out[i + k] * coefficients[j * 8 + k];
|
|
}
|
|
block[i + j] = floor(tmp + 0.499999999999);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Transform 8x8 block of data with a double precision inverse DCT <br>
|
|
* This is a reference implementation.
|
|
*
|
|
* @param block pointer to 8x8 block of data to transform
|
|
*/
|
|
void ff_ref_idct(short *block)
|
|
{
|
|
/* implement the equation: block = (coefficients') * block * coefficients */
|
|
|
|
unsigned int i, j, k;
|
|
double out[8 * 8];
|
|
|
|
/* out = block * coefficients */
|
|
for (i = 0; i < 64; i += 8) {
|
|
for (j = 0; j < 8; ++j) {
|
|
double tmp = 0;
|
|
for (k = 0; k < 8; ++k) {
|
|
tmp += block[i + k] * coefficients[k * 8 + j];
|
|
}
|
|
out[i + j] = tmp;
|
|
}
|
|
}
|
|
|
|
/* block = (coefficients') * out */
|
|
for (i = 0; i < 8; ++i) {
|
|
for (j = 0; j < 8; ++j) {
|
|
double tmp = 0;
|
|
for (k = 0; k < 64; k += 8) {
|
|
tmp += coefficients[k + i] * out[k + j];
|
|
}
|
|
block[i * 8 + j] = floor(tmp + 0.5);
|
|
}
|
|
}
|
|
}
|