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