278c308cea
This will be used later in both the mpeg2_metadata filter and the VAAPI MPEG-2 encoder. Also adds a unit test. (cherry picked from commit b5859e0b04bdbe12c97cb12ac10a45d51d2d73c9)
104 lines
2.9 KiB
C
104 lines
2.9 KiB
C
/*
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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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#include "libavutil/rational.h"
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#include "mpeg12.h"
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#include "mpeg12data.h"
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const AVRational ff_mpeg12_frame_rate_tab[16] = {
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{ 0, 0},
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{24000, 1001},
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{ 24, 1},
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{ 25, 1},
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{30000, 1001},
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{ 30, 1},
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{ 50, 1},
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{60000, 1001},
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{ 60, 1},
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// Xing's 15fps: (9)
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{ 15, 1},
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// libmpeg3's "Unofficial economy rates": (10-13)
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{ 5, 1},
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{ 10, 1},
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{ 12, 1},
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{ 15, 1},
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{ 0, 0},
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};
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void ff_mpeg12_find_best_frame_rate(AVRational frame_rate,
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int *code, int *ext_n, int *ext_d,
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int nonstandard)
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{
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int mpeg2 = ext_n && ext_d;
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int max_code = nonstandard ? 12 : 8;
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int c, n, d, best_c, best_n, best_d;
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AVRational best_error = { INT_MAX, 1 };
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// Default to NTSC if the inputs make no sense.
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best_c = 4;
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best_n = best_d = 1;
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for (c = 1; c <= max_code; c++) {
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if (av_cmp_q(frame_rate, ff_mpeg12_frame_rate_tab[c]) == 0) {
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best_c = c;
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goto found;
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}
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}
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for (c = 1; c <= max_code; c++) {
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for (n = 1; n <= (mpeg2 ? 4 : 1); n++) {
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for (d = 1; d <= (mpeg2 ? 32 : 1); d++) {
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AVRational test, error;
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int cmp;
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test = av_mul_q(ff_mpeg12_frame_rate_tab[c],
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(AVRational) { n, d });
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cmp = av_cmp_q(test, frame_rate);
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if (cmp == 0) {
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best_c = c;
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best_n = n;
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best_d = d;
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goto found;
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}
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if (cmp < 0)
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error = av_div_q(frame_rate, test);
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else
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error = av_div_q(test, frame_rate);
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cmp = av_cmp_q(error, best_error);
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if (cmp < 0 || (cmp == 0 && n == 1 && d == 1)) {
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best_c = c;
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best_n = n;
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best_d = d;
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best_error = error;
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}
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}
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}
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}
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found:
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*code = best_c;
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if (mpeg2) {
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*ext_n = best_n - 1;
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*ext_d = best_d - 1;
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}
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}
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