yading@10: /*
yading@10:  * reference discrete cosine transform (double precision)
yading@10:  * Copyright (C) 2009 Dylan Yudaken
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * reference discrete cosine transform (double precision)
yading@10:  *
yading@10:  * @author Dylan Yudaken (dyudaken at gmail)
yading@10:  *
yading@10:  * @note This file could be optimized a lot, but is for
yading@10:  * reference and so readability is better.
yading@10:  */
yading@10: 
yading@10: #include "libavutil/mathematics.h"
yading@10: #include "dctref.h"
yading@10: 
yading@10: static double coefficients[8 * 8];
yading@10: 
yading@10: /**
yading@10:  * Initialize the double precision discrete cosine transform
yading@10:  * functions fdct & idct.
yading@10:  */
yading@10: av_cold void ff_ref_dct_init(void)
yading@10: {
yading@10:     unsigned int i, j;
yading@10: 
yading@10:     for (j = 0; j < 8; ++j) {
yading@10:         coefficients[j] = sqrt(0.125);
yading@10:         for (i = 8; i < 64; i += 8) {
yading@10:             coefficients[i + j] = 0.5 * cos(i * (j + 0.5) * M_PI / 64.0);
yading@10:         }
yading@10:     }
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * Transform 8x8 block of data with a double precision forward DCT <br>
yading@10:  * This is a reference implementation.
yading@10:  *
yading@10:  * @param block pointer to 8x8 block of data to transform
yading@10:  */
yading@10: void ff_ref_fdct(short *block)
yading@10: {
yading@10:     /* implement the equation: block = coefficients * block * coefficients' */
yading@10: 
yading@10:     unsigned int i, j, k;
yading@10:     double out[8 * 8];
yading@10: 
yading@10:     /* out = coefficients * block */
yading@10:     for (i = 0; i < 64; i += 8) {
yading@10:         for (j = 0; j < 8; ++j) {
yading@10:             double tmp = 0;
yading@10:             for (k = 0; k < 8; ++k) {
yading@10:                 tmp += coefficients[i + k] * block[k * 8 + j];
yading@10:             }
yading@10:             out[i + j] = tmp * 8;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     /* block = out * (coefficients') */
yading@10:     for (j = 0; j < 8; ++j) {
yading@10:         for (i = 0; i < 64; i += 8) {
yading@10:             double tmp = 0;
yading@10:             for (k = 0; k < 8; ++k) {
yading@10:                 tmp += out[i + k] * coefficients[j * 8 + k];
yading@10:             }
yading@10:             block[i + j] = floor(tmp + 0.499999999999);
yading@10:         }
yading@10:     }
yading@10: }
yading@10: 
yading@10: /**
yading@10:  * Transform 8x8 block of data with a double precision inverse DCT <br>
yading@10:  * This is a reference implementation.
yading@10:  *
yading@10:  * @param block pointer to 8x8 block of data to transform
yading@10:  */
yading@10: void ff_ref_idct(short *block)
yading@10: {
yading@10:     /* implement the equation: block = (coefficients') * block * coefficients */
yading@10: 
yading@10:     unsigned int i, j, k;
yading@10:     double out[8 * 8];
yading@10: 
yading@10:     /* out = block * coefficients */
yading@10:     for (i = 0; i < 64; i += 8) {
yading@10:         for (j = 0; j < 8; ++j) {
yading@10:             double tmp = 0;
yading@10:             for (k = 0; k < 8; ++k) {
yading@10:                 tmp += block[i + k] * coefficients[k * 8 + j];
yading@10:             }
yading@10:             out[i + j] = tmp;
yading@10:         }
yading@10:     }
yading@10: 
yading@10:     /* block = (coefficients') * out */
yading@10:     for (i = 0; i < 8; ++i) {
yading@10:         for (j = 0; j < 8; ++j) {
yading@10:             double tmp = 0;
yading@10:             for (k = 0; k < 64; k += 8) {
yading@10:                 tmp += coefficients[k + i] * out[k + j];
yading@10:             }
yading@10:             block[i * 8 + j] = floor(tmp + 0.5);
yading@10:         }
yading@10:     }
yading@10: }