68 lines
2.0 KiB
C
68 lines
2.0 KiB
C
/******************************************************************************
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Copyright (C) 2022 by Hugh Bailey <obs.jim@gmail.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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******************************************************************************/
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#include "obs-nal.h"
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/* NOTE: I noticed that FFmpeg does some unusual special handling of certain
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* scenarios that I was unaware of, so instead of just searching for {0, 0, 1}
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* we'll just use the code from FFmpeg - http://www.ffmpeg.org/ */
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static const uint8_t *ff_avc_find_startcode_internal(const uint8_t *p,
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const uint8_t *end)
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{
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const uint8_t *a = p + 4 - ((intptr_t)p & 3);
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for (end -= 3; p < a && p < end; p++) {
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if (p[0] == 0 && p[1] == 0 && p[2] == 1)
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return p;
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}
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for (end -= 3; p < end; p += 4) {
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uint32_t x = *(const uint32_t *)p;
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if ((x - 0x01010101) & (~x) & 0x80808080) {
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if (p[1] == 0) {
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if (p[0] == 0 && p[2] == 1)
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return p;
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if (p[2] == 0 && p[3] == 1)
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return p + 1;
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}
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if (p[3] == 0) {
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if (p[2] == 0 && p[4] == 1)
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return p + 2;
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if (p[4] == 0 && p[5] == 1)
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return p + 3;
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}
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}
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}
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for (end += 3; p < end; p++) {
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if (p[0] == 0 && p[1] == 0 && p[2] == 1)
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return p;
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}
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return end + 3;
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}
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const uint8_t *obs_nal_find_startcode(const uint8_t *p, const uint8_t *end)
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{
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const uint8_t *out = ff_avc_find_startcode_internal(p, end);
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if (p < out && out < end && !out[-1])
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out--;
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return out;
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}
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