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c4584f3c1f
According to newer RFCs, this packetization scheme should only be used for interfacing with legacy systems. Implementing this packetization mode properly requires parsing the full H263 bitstream to find macroblock boundaries (and knowing their macroblock and gob numbers and motion vector predictors). This implementation tries to look for GOB headers (which can be inserted by using -ps <small number>), but if the GOBs aren't small enough to fit into the MTU, the packetizer blindly splits packets at any offset and claims it to be a GOB boundary (by using Mode A from the RFC). While not correct, this seems to work with some receivers. Signed-off-by: Martin Storsjö <martin@martin.st>
82 lines
2.4 KiB
C
82 lines
2.4 KiB
C
/*
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* RTP packetization for H.263 video
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* Copyright (c) 2009 Luca Abeni
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* Copyright (c) 2009 Martin Storsjo
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*
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* This file is part of Libav.
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*
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* Libav 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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* Libav 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 Libav; 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 "avformat.h"
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#include "rtpenc.h"
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const uint8_t *ff_h263_find_resync_marker_reverse(const uint8_t *restrict start,
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const uint8_t *restrict end)
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{
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const uint8_t *p = end - 1;
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start += 1; /* Make sure we never return the original start. */
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for (; p > start; p -= 2) {
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if (!*p) {
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if (!p[ 1] && p[2]) return p;
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else if (!p[-1] && p[1]) return p - 1;
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}
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}
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return end;
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}
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/**
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* Packetize H.263 frames into RTP packets according to RFC 4629
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*/
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void ff_rtp_send_h263(AVFormatContext *s1, const uint8_t *buf1, int size)
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{
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RTPMuxContext *s = s1->priv_data;
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int len, max_packet_size;
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uint8_t *q;
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max_packet_size = s->max_payload_size;
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while (size > 0) {
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q = s->buf;
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if (size >= 2 && (buf1[0] == 0) && (buf1[1] == 0)) {
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*q++ = 0x04;
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buf1 += 2;
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size -= 2;
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} else {
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*q++ = 0;
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}
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*q++ = 0;
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len = FFMIN(max_packet_size - 2, size);
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/* Look for a better place to split the frame into packets. */
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if (len < size) {
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const uint8_t *end = ff_h263_find_resync_marker_reverse(buf1,
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buf1 + len);
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len = end - buf1;
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}
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memcpy(q, buf1, len);
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q += len;
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/* 90 KHz time stamp */
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s->timestamp = s->cur_timestamp;
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ff_rtp_send_data(s1, s->buf, q - s->buf, (len == size));
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buf1 += len;
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size -= len;
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}
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}
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