168 lines
6.4 KiB
C
168 lines
6.4 KiB
C
/*
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* Copyright (c) 2016 William Ma, Sofia Kim, Dustin Woo
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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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* Optimal Huffman Encoding tests.
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*/
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#include "libavcodec/avcodec.h"
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#include <stdlib.h>
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#include "libavcodec/mjpegenc.h"
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#include "libavcodec/mjpegenc_huffman.h"
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#include "libavcodec/mjpegenc_common.h"
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#include "libavcodec/mpegvideo.h"
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// Validate the computed lengths satisfy the JPEG restrictions and is optimal.
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static int check_lengths(int L, int expected_length,
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const int *probs, int nprobs)
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{
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HuffTable lengths[256];
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PTable val_counts[256];
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int actual_length = 0, i, j, k, prob, length;
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int ret = 0;
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double cantor_measure = 0;
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av_assert0(nprobs <= 256);
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for (i = 0; i < nprobs; i++) {
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val_counts[i] = (PTable){.value = i, .prob = probs[i]};
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}
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ff_mjpegenc_huffman_compute_bits(val_counts, lengths, nprobs, L);
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for (i = 0; i < nprobs; i++) {
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// Find the value's prob and length
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for (j = 0; j < nprobs; j++)
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if (val_counts[j].value == i) break;
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for (k = 0; k < nprobs; k++)
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if (lengths[k].code == i) break;
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if (!(j < nprobs && k < nprobs)) return 1;
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prob = val_counts[j].prob;
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length = lengths[k].length;
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if (prob) {
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actual_length += prob * length;
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cantor_measure += 1. / (1 << length);
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}
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if (length > L || length < 1) return 1;
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}
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// Check that the codes can be prefix-free.
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if (cantor_measure > 1) ret = 1;
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// Check that the total length is optimal
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if (actual_length != expected_length) ret = 1;
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if (ret == 1) {
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fprintf(stderr,
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"Cantor measure: %f\n"
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"Actual length: %d\n"
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"Expected length: %d\n",
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cantor_measure, actual_length, expected_length);
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}
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return ret;
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}
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static const int probs_zeroes[] = {
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6, 6, 0, 0, 0
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};
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static const int probs_skewed[] = {
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2, 0, 0, 0, 0, 1, 0, 0, 20, 0, 2, 0, 10, 5, 1, 1, 9, 1, 1, 6, 0, 5, 0, 1, 0, 7, 6,
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1, 1, 5, 0, 0, 0, 0, 11, 0, 0, 0, 51, 1, 0, 20, 0, 1, 0, 0, 0, 0, 6, 106, 1, 0, 1,
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0, 2, 1, 16, 0, 0, 5, 0, 0, 0, 4, 3, 15, 4, 4, 0, 0, 0, 3, 0, 0, 1, 0, 3, 0, 3, 2,
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2, 0, 0, 4, 3, 40, 1, 2, 0, 22, 0, 0, 0, 9, 0, 0, 0, 0, 1, 1, 0, 1, 6, 11, 4, 10,
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28, 6, 1, 0, 0, 9, 9, 4, 0, 0, 0, 0, 8, 33844, 2, 0, 2, 1, 1, 5, 0, 0, 1, 9, 1, 0,
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4, 14, 4, 0, 0, 3, 8, 0, 51, 9, 6, 1, 1, 2, 2, 3, 1, 5, 5, 29, 0, 0, 0, 0, 14, 29,
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6, 4, 13, 12, 2, 3, 1, 0, 5, 4, 1, 1, 0, 0, 29, 1, 0, 0, 0, 0, 4, 0, 0, 1, 0, 1,
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7, 0, 42, 0, 0, 0, 0, 0, 2, 0, 3, 9, 0, 0, 0, 2, 1, 0, 0, 6, 5, 6, 1, 2, 3, 0, 0,
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0, 3, 0, 0, 28, 0, 2, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 23, 0, 0, 0, 0,
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0, 21, 1, 0, 3, 24, 2, 0, 0, 7, 0, 0, 1, 5, 1, 2, 0, 5
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};
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static const int probs_sat[] = {
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74, 8, 14, 7, 9345, 40, 0, 2014, 2, 1, 115, 0, 2, 1, 194, 388, 20, 0, 0, 2, 1, 121,
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1, 1583, 0, 16, 21, 2, 132, 2, 15, 9, 13, 1, 0, 2293, 2, 8, 5, 2, 30, 0, 0, 4, 54,
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783, 4, 1, 2, 4, 0, 22, 93, 1, 143, 19, 0, 36, 32, 4, 6, 33, 3, 45, 0, 8, 1, 0, 18,
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17, 1, 0, 1, 0, 0, 1, 1004, 38, 3, 8, 90, 23, 0, 2819, 3, 0, 970, 158, 9, 6, 4, 48,
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4, 0, 1, 0, 0, 60, 3, 62, 0, 2, 2, 2, 279, 66, 16, 1, 20, 0, 7, 9, 32, 1411, 6, 3,
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27, 1, 5, 49, 0, 0, 0, 0, 0, 2, 10, 1, 1, 2, 3, 801, 3, 25, 5, 1, 1, 0, 632, 0, 14,
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18, 5, 8, 200, 4, 4, 22, 12, 0, 4, 1, 0, 2, 4, 9, 3, 16, 7, 2, 2, 213, 0, 2, 620,
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39303, 0, 1, 0, 2, 1, 183781, 1, 0, 0, 0, 94, 7, 3, 4, 0, 4, 306, 43, 352, 76, 34,
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13, 11, 0, 51, 1, 13, 19, 0, 26, 0, 7276, 4, 207, 31, 1, 2, 4, 6, 19, 8, 17, 4, 6,
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0, 1085, 0, 0, 0, 3, 489, 36, 1, 0, 1, 9420, 294, 28, 0, 57, 5, 0, 9, 2, 0, 1, 2,
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2, 0, 0, 9, 2, 29, 2, 2, 7, 0, 5, 490, 0, 7, 5, 0, 1, 8, 0, 0, 23255, 0, 1
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};
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// Test the example given on @see
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// http://guru.multimedia.cx/small-tasks-for-ffmpeg/
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int main(int argc, char **argv)
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{
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int i, ret = 0;
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// Probabilities of symbols 0..4
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PTable val_counts[] = {
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{.value = 0, .prob = 1},
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{.value = 1, .prob = 2},
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{.value = 2, .prob = 5},
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{.value = 3, .prob = 10},
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{.value = 4, .prob = 21},
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};
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// Expected code lengths for each symbol
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static const HuffTable expected[] = {
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{.code = 0, .length = 3},
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{.code = 1, .length = 3},
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{.code = 2, .length = 3},
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{.code = 3, .length = 3},
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{.code = 4, .length = 1},
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};
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// Actual code lengths
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HuffTable distincts[5];
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// Build optimal huffman tree using an internal function, to allow for
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// smaller-than-normal test cases. This mutates val_counts by sorting.
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ff_mjpegenc_huffman_compute_bits(val_counts, distincts,
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FF_ARRAY_ELEMS(distincts), 3);
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for (i = 0; i < FF_ARRAY_ELEMS(distincts); i++) {
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if (distincts[i].code != expected[i].code ||
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distincts[i].length != expected[i].length) {
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fprintf(stderr,
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"Built huffman does not equal expectations. "
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"Expected: code %d probability %d, "
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"Actual: code %d probability %d\n",
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expected[i].code, expected[i].length,
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distincts[i].code, distincts[i].length);
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ret = 1;
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}
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}
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// Check handling of zero probabilities
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if (check_lengths(16, 18, probs_zeroes, FF_ARRAY_ELEMS(probs_zeroes)))
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ret = 1;
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// Check skewed distribution over 256 without saturated lengths
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if (check_lengths(16, 41282, probs_skewed, FF_ARRAY_ELEMS(probs_skewed)))
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ret = 1;
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// Check skewed distribution over 256 with saturated lengths
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if (check_lengths(16, 669904, probs_sat, FF_ARRAY_ELEMS(probs_sat)))
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ret = 1;
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return ret;
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}
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