/*
  * 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;

     }
 }