aac5773f
 hucm
功能基本完成，接口待打磨
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/*
* 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
*/
#include "libavutil/rational.h"
#include "mpeg12.h"
#include "mpeg12data.h"
const AVRational ff_mpeg12_frame_rate_tab[16] = {
{ 0, 0},
{24000, 1001},
{ 24, 1},
{ 25, 1},
{30000, 1001},
{ 30, 1},
{ 50, 1},
{60000, 1001},
{ 60, 1},
// Xing's 15fps: (9)
{ 15, 1},
// libmpeg3's "Unofficial economy rates": (10-13)
{ 5, 1},
{ 10, 1},
{ 12, 1},
{ 15, 1},
{ 0, 0},
};
void ff_mpeg12_find_best_frame_rate(AVRational frame_rate,
int *code, int *ext_n, int *ext_d,
int nonstandard)
{
int mpeg2 = ext_n && ext_d;
int max_code = nonstandard ? 12 : 8;
int c, n, d, best_c, best_n, best_d;
AVRational best_error = { INT_MAX, 1 };
// Default to NTSC if the inputs make no sense.
best_c = 4;
best_n = best_d = 1;
for (c = 1; c <= max_code; c++) {
if (av_cmp_q(frame_rate, ff_mpeg12_frame_rate_tab[c]) == 0) {
best_c = c;
goto found;
}
}
for (c = 1; c <= max_code; c++) {
for (n = 1; n <= (mpeg2 ? 4 : 1); n++) {
for (d = 1; d <= (mpeg2 ? 32 : 1); d++) {
AVRational test, error;
int cmp;
test = av_mul_q(ff_mpeg12_frame_rate_tab[c],
(AVRational) { n, d });
cmp = av_cmp_q(test, frame_rate);
if (cmp == 0) {
best_c = c;
best_n = n;
best_d = d;
goto found;
}
if (cmp < 0)
error = av_div_q(frame_rate, test);
else
error = av_div_q(test, frame_rate);
cmp = av_cmp_q(error, best_error);
if (cmp < 0 || (cmp == 0 && n == 1 && d == 1)) {
best_c = c;
best_n = n;
best_d = d;
best_error = error;
}
}
}
}
found:
*code = best_c;
if (mpeg2) {
*ext_n = best_n - 1;
*ext_d = best_d - 1;
}
}
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