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  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. const uint8_t *ff_h263_find_resync_marker_reverse(const uint8_t *av_restrict start,
  27.                                                   const uint8_t *av_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 (size >= 2 && (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 = ff_h263_find_resync_marker_reverse(buf1,
  67.                                                                     buf1 + len);
  68.             len = end - buf1;
  69.         }
  70.  
  71.         memcpy(q, buf1, len);
  72.         q += len;
  73.  
  74.         /* 90 KHz time stamp */
  75.         s->timestamp = s->cur_timestamp;
  76.         ff_rtp_send_data(s1, s->buf, q - s->buf, (len == size));
  77.  
  78.         buf1 += len;
  79.         size -= len;
  80.     }
  81. }
  82.