GCC Code Coverage Report
Directory: ../../../ffmpeg/ Exec Total Coverage
File: src/libavcodec/dctref.c Lines: 34 34 100.0 %
Date: 2019-11-22 03:34:36 Branches: 28 28 100.0 %

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