libavformat/rtp_h263.c

   1 /*
   2  * RTP packetization for H.263 video
   3  * Copyright (c) 2009 Luca Abeni
   4  * Copyright (c) 2009 Martin Storsjo
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "avformat.h"
  24 #include "rtpenc.h"
  25
  26 static const uint8_t *find_resync_marker_reverse(const uint8_t *restrict start,
  27                                                  const uint8_t *restrict end)
  28 {
  29     const uint8_t *p = end - 1;
  30     start += 1; /* Make sure we never return the original start. */
  31     for (; p > start; p -= 2) {
  32         if (!*p) {
  33             if      (!p[ 1] && p[2]) return p;
  34             else if (!p[-1] && p[1]) return p - 1;
  35         }
  36     }
  37     return end;
  38 }
  39
  40 /**
  41  * Packetize H.263 frames into RTP packets according to RFC 4629
  42  */
  43 void ff_rtp_send_h263(AVFormatContext *s1, const uint8_t *buf1, int size)
  44 {
  45     RTPMuxContext *s = s1->priv_data;
  46     int len, max_packet_size;
  47     uint8_t *q;
  48
  49     max_packet_size = s->max_payload_size;
  50
  51     while (size > 0) {
  52         q = s->buf;
  53         if ((buf1[0] == 0) && (buf1[1] == 0)) {
  54             *q++ = 0x04;
  55             buf1 += 2;
  56             size -= 2;
  57         } else {
  58             *q++ = 0;
  59         }
  60         *q++ = 0;
  61
  62         len = FFMIN(max_packet_size - 2, size);
  63
  64         /* Look for a better place to split the frame into packets. */
  65         if (len < size) {
  66             const uint8_t *end = find_resync_marker_reverse(buf1, buf1 + len);
  67             len = end - buf1;
  68         }
  69
  70         memcpy(q, buf1, len);
  71         q += len;
  72
  73         /* 90 KHz time stamp */
  74         s->timestamp = s->cur_timestamp;
  75         ff_rtp_send_data(s1, s->buf, q - s->buf, (len == size));
  76
  77         buf1 += len;
  78         size -= len;
  79     }
  80 }