text: /*
   * RTP packetization for H.263 video
   * Copyright (c) 2012 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"
  #include "libavcodec/put_bits.h"
  #include "libavcodec/get_bits.h"
  
  struct H263Info {
      int src;
      int i;
      int u;
      int s;
      int a;
      int pb;
      int tr;
  };
  
  struct H263State {
      int gobn;
      int mba;
      int hmv1, vmv1, hmv2, vmv2;
      int quant;
  };
  
  static void send_mode_a(AVFormatContext *s1, const struct H263Info *info,
                          const uint8_t *buf, int len, int ebits, int m)
  {
      RTPMuxContext *s = s1->priv_data;
      PutBitContext pb;
  
      init_put_bits(&pb, s->buf, 32);
      put_bits(&pb, 1, 0); /* F - 0, mode A */
      put_bits(&pb, 1, 0); /* P - 0, normal I/P */
      put_bits(&pb, 3, 0); /* SBIT - 0 bits */
      put_bits(&pb, 3, ebits); /* EBIT */
      put_bits(&pb, 3, info->src); /* SRC - source format */
      put_bits(&pb, 1, info->i); /* I - inter/intra */
      put_bits(&pb, 1, info->u); /* U - unrestricted motion vector */
      put_bits(&pb, 1, info->s); /* S - syntax-baesd arithmetic coding */
      put_bits(&pb, 1, info->a); /* A - advanced prediction */
      put_bits(&pb, 4, 0); /* R - reserved */
      put_bits(&pb, 2, 0); /* DBQ - 0 */
      put_bits(&pb, 3, 0); /* TRB - 0 */
      put_bits(&pb, 8, info->tr); /* TR */
      flush_put_bits(&pb);
      memcpy(s->buf + 4, buf, len);
  
      ff_rtp_send_data(s1, s->buf, len + 4, m);
  }
  
  static void send_mode_b(AVFormatContext *s1, const struct H263Info *info,
                          const struct H263State *state, const uint8_t *buf,
                          int len, int sbits, int ebits, int m)
  {
      RTPMuxContext *s = s1->priv_data;
      PutBitContext pb;
  
      init_put_bits(&pb, s->buf, 64);
      put_bits(&pb, 1, 1); /* F - 1, mode B */
      put_bits(&pb, 1, 0); /* P - 0, mode B */
      put_bits(&pb, 3, sbits); /* SBIT - 0 bits */
      put_bits(&pb, 3, ebits); /* EBIT - 0 bits */
      put_bits(&pb, 3, info->src); /* SRC - source format */
      put_bits(&pb, 5, state->quant); /* QUANT - quantizer for the first MB */
      put_bits(&pb, 5, state->gobn); /* GOBN - GOB number */
      put_bits(&pb, 9, state->mba); /* MBA - MB address */
      put_bits(&pb, 2, 0); /* R - reserved */
      put_bits(&pb, 1, info->i); /* I - inter/intra */
      put_bits(&pb, 1, info->u); /* U - unrestricted motion vector */
      put_bits(&pb, 1, info->s); /* S - syntax-baesd arithmetic coding */
      put_bits(&pb, 1, info->a); /* A - advanced prediction */
      put_bits(&pb, 7, state->hmv1); /* HVM1 - horizontal motion vector 1 */
      put_bits(&pb, 7, state->vmv1); /* VMV1 - vertical motion vector 1 */
      put_bits(&pb, 7, state->hmv2); /* HVM2 - horizontal motion vector 2 */
      put_bits(&pb, 7, state->vmv2); /* VMV2 - vertical motion vector 2 */
      flush_put_bits(&pb);
      memcpy(s->buf + 8, buf, len);
  
      ff_rtp_send_data(s1, s->buf, len + 8, m);
  }
  
  void ff_rtp_send_h263_rfc2190(AVFormatContext *s1, const uint8_t *buf, int size,
                                const uint8_t *mb_info, int mb_info_size)
  {
      RTPMuxContext *s = s1->priv_data;
      int len, sbits = 0, ebits = 0;
      GetBitContext gb;
      struct H263Info info = { 0 };
      struct H263State state = { 0 };
      int mb_info_pos = 0, mb_info_count = mb_info_size / 12;
      const uint8_t *buf_base = buf;
  
      s->timestamp = s->cur_timestamp;
  
      init_get_bits(&gb, buf, size*8);
      if (get_bits(&gb, 22) == 0x20) { /* Picture Start Code */
          info.tr  = get_bits(&gb, 8);
          skip_bits(&gb, 2); /* PTYPE start, H.261 disambiguation */
          skip_bits(&gb, 3); /* Split screen, document camera, freeze picture release */
          info.src = get_bits(&gb, 3);
          info.i   = get_bits(&gb, 1);
          info.u   = get_bits(&gb, 1);
          info.s   = get_bits(&gb, 1);
          info.a   = get_bits(&gb, 1);
          info.pb  = get_bits(&gb, 1);
      }
  
      while (size > 0) {
          struct H263State packet_start_state = state;
          len = FFMIN(s->max_payload_size - 8, 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(buf,
                                                                      buf + len);
              len = end - buf;
              if (len == s->max_payload_size - 8) {
                  /* Skip mb info prior to the start of the current ptr */
                  while (mb_info_pos < mb_info_count) {
                      uint32_t pos = AV_RL32(&mb_info[12*mb_info_pos])/8;
                      if (pos >= buf - buf_base)
                          break;
                      mb_info_pos++;
                  }
                  /* Find the first mb info past the end pointer */
                  while (mb_info_pos + 1 < mb_info_count) {
                      uint32_t pos = AV_RL32(&mb_info[12*(mb_info_pos + 1)])/8;
                      if (pos >= end - buf_base)
                          break;
                      mb_info_pos++;
                  }
                  if (mb_info_pos < mb_info_count) {
                      const uint8_t *ptr = &mb_info[12*mb_info_pos];
                      /* get position in bits in the input packet at which the next info block should be used */
                      uint32_t bit_pos = AV_RL32(ptr);
                      /* get position in bytes */
                      uint32_t pos_next_mb_info = (bit_pos + 7)/8;
                      /* check if data from the next MB info block should be used */
                      if (pos_next_mb_info <= end - buf_base) {
                          state.quant = ptr[4];
                          state.gobn  = ptr[5];
                          state.mba   = AV_RL16(&ptr[6]);
                          state.hmv1  = (int8_t) ptr[8];
                          state.vmv1  = (int8_t) ptr[9];
                          state.hmv2  = (int8_t) ptr[10];
                          state.vmv2  = (int8_t) ptr[11];
                          ebits = 8 * pos_next_mb_info - bit_pos;
                          len   = pos_next_mb_info - (buf - buf_base);
                          mb_info_pos++;
                      }
                  } else {
                      av_log(s1, AV_LOG_ERROR, "Unable to split H.263 packet, "
                             "use -mb_info %d or -ps 1.\n",
                             s->max_payload_size - 8);
                  }
              }
          }
  
          if (size > 2 && !buf[0] && !buf[1])
              send_mode_a(s1, &info, buf, len, ebits, len == size);
          else
              send_mode_b(s1, &info, &packet_start_state, buf, len, sbits,
                          ebits, len == size);
  
          if (ebits) {
              sbits = 8 - ebits;
              len--;
          } else {
              sbits = 0;
          }
          buf  += len;
          size -= len;
          ebits = 0;
      }
  }
  