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ffmpeg-4.2.2/libavformat/rtpenc_h263.c 2.41 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * RTP packetization for H.263 video
   * Copyright (c) 2009 Luca Abeni
   * Copyright (c) 2009 Martin Storsjo
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "avformat.h"
  #include "rtpenc.h"
  
  const uint8_t *ff_h263_find_resync_marker_reverse(const uint8_t *av_restrict start,
                                                    const uint8_t *av_restrict end)
  {
      const uint8_t *p = end - 1;
      start += 1; /* Make sure we never return the original start. */
      for (; p > start; p -= 2) {
          if (!*p) {
              if      (!p[ 1] && p[2]) return p;
              else if (!p[-1] && p[1]) return p - 1;
          }
      }
      return end;
  }
  
  /**
   * Packetize H.263 frames into RTP packets according to RFC 4629
   */
  void ff_rtp_send_h263(AVFormatContext *s1, const uint8_t *buf1, int size)
  {
      RTPMuxContext *s = s1->priv_data;
      int len, max_packet_size;
      uint8_t *q;
  
      max_packet_size = s->max_payload_size;
  
      while (size > 0) {
          q = s->buf;
          if (size >= 2 && (buf1[0] == 0) && (buf1[1] == 0)) {
              *q++ = 0x04;
              buf1 += 2;
              size -= 2;
          } else {
              *q++ = 0;
          }
          *q++ = 0;
  
          len = FFMIN(max_packet_size - 2, size);
  
          /* Look for a better place to split the frame into packets. */
          if (len < size) {
              const uint8_t *end = ff_h263_find_resync_marker_reverse(buf1,
                                                                      buf1 + len);
              len = end - buf1;
          }
  
          memcpy(q, buf1, len);
          q += len;
  
          /* 90 KHz time stamp */
          s->timestamp = s->cur_timestamp;
          ff_rtp_send_data(s1, s->buf, q - s->buf, (len == size));
  
          buf1 += len;
          size -= len;
      }
  }