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https://github.com/FFmpeg/FFmpeg.git
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mpeg12: Add a common function to find the best frame rate
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 b5859e0b04)
This commit is contained in:
Mark Thompson
parent
03f982bbca
commit
278c308cea
@ -1090,6 +1090,7 @@ TESTPROGS-$(CONFIG_GOLOMB) += golomb
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TESTPROGS-$(CONFIG_IDCTDSP) += dct
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TESTPROGS-$(CONFIG_IIRFILTER) += iirfilter
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TESTPROGS-$(HAVE_MMX) += motion
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TESTPROGS-$(CONFIG_MPEGVIDEO) += mpeg12framerate
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TESTPROGS-$(CONFIG_RANGECODER) += rangecoder
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TESTPROGS-$(CONFIG_SNOW_ENCODER) += snowenc
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@ -73,4 +73,8 @@ void ff_mpeg1_encode_mb(MpegEncContext *s, int16_t block[8][64],
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void ff_mpeg1_encode_init(MpegEncContext *s);
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void ff_mpeg1_encode_slice_header(MpegEncContext *s);
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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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#endif /* AVCODEC_MPEG12_H */
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@ -18,6 +18,9 @@
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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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@ -37,3 +40,64 @@ const AVRational ff_mpeg12_frame_rate_tab[16] = {
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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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87
libavcodec/tests/mpeg12framerate.c
Normal file
87
libavcodec/tests/mpeg12framerate.c
Normal file
@ -0,0 +1,87 @@
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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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#include "libavcodec/mpeg12.h"
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#include "libavcodec/mpeg12data.h"
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int main(void)
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{
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int i;
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#define TEST_MATCH(frame_rate, code, ext_n, ext_d) do { \
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AVRational fr = frame_rate; \
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int c, n, d; \
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ff_mpeg12_find_best_frame_rate(fr, &c, &n, &d, 0); \
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if (c != code || n != ext_n || d != ext_d) { \
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av_log(NULL, AV_LOG_ERROR, "Failed to match %d/%d: " \
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"code = %d, ext_n = %d, ext_d = %d.\n", \
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fr.num, fr.den, c, n, d); \
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return 1; \
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} \
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} while (0)
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#define TEST_EXACT(frn, frd) do { \
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AVRational fr = (AVRational) { frn, frd }; \
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int c, n, d; \
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ff_mpeg12_find_best_frame_rate(fr, &c, &n, &d, 0); \
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if (av_cmp_q(fr, av_mul_q(ff_mpeg12_frame_rate_tab[c], \
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(AVRational) { n + 1, d + 1 })) != 0) { \
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av_log(NULL, AV_LOG_ERROR, "Failed to find exact %d/%d: " \
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"code = %d, ext_n = %d, ext_d = %d.\n", \
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fr.num, fr.den, c, n, d); \
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return 1; \
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} \
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} while (0)
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// Framerates in the table must be chosen exactly.
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for (i = 1; i <= 8; i++)
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TEST_MATCH(ff_mpeg12_frame_rate_tab[i], i, 0, 0);
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// As should the same ones with small perturbations.
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// (1/1000 used here to be smaller than half the difference
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// between 24 and 24000/1001.)
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for (i = 1; i <= 8; i++) {
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TEST_MATCH(av_sub_q(ff_mpeg12_frame_rate_tab[i],
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(AVRational) { 1, 1000 }), i, 0, 0);
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TEST_MATCH(av_add_q(ff_mpeg12_frame_rate_tab[i],
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(AVRational) { 1, 1000 }), i, 0, 0);
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}
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// Exactly constructable framerates should be exact. Note that some
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// values can be made in multiple ways (e.g. 12 = 24 / 2 == 60 / 5),
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// and there is no reason to favour any particular choice.
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TEST_EXACT( 1, 1);
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TEST_EXACT( 2, 1);
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TEST_EXACT( 12, 1);
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TEST_EXACT( 15000, 1001);
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TEST_EXACT( 15, 1);
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TEST_EXACT( 120, 1);
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TEST_EXACT(120000, 1001);
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TEST_EXACT( 200, 1);
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TEST_EXACT( 240, 1);
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// Values higher than 240 (the highest representable, as 60 * 4 / 1)
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// should be mapped to 240.
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for (i = 240; i < 1000; i += 10)
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TEST_MATCH(((AVRational) { i, 1 }), 8, 3, 0);
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// Values lower than 24000/32032 (the lowest representable, as
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// 24000/1001 * 1 / 32) should be mapped to 24000/32032.
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for (i = 74; i > 0; i--)
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TEST_MATCH(((AVRational) { i, 100 }), 1, 0, 31);
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return 0;
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}
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@ -45,6 +45,11 @@ FATE_LIBAVCODEC-$(CONFIG_IIRFILTER) += fate-iirfilter
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fate-iirfilter: libavcodec/tests/iirfilter$(EXESUF)
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fate-iirfilter: CMD = run libavcodec/tests/iirfilter
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FATE_LIBAVCODEC-$(CONFIG_MPEGVIDEO) += fate-mpeg12framerate
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fate-mpeg12framerate: libavcodec/tests/mpeg12framerate$(EXESUF)
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fate-mpeg12framerate: CMD = run libavcodec/tests/mpeg12framerate
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fate-mpeg12framerate: REF = /dev/null
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FATE_LIBAVCODEC-yes += fate-libavcodec-options
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fate-libavcodec-options: libavcodec/tests/options$(EXESUF)
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fate-libavcodec-options: CMD = run libavcodec/tests/options
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