text: /*
   * MPEG4 Video frame extraction
   * Copyright (c) 2003 Fabrice Bellard
   * Copyright (c) 2003 Michael Niedermayer
   *
   * 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 "parser.h"
  #include "mpegvideo.h"
  #include "mpeg4video_parser.h"
  
  
  int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
      int vop_found, i;
      uint32_t state;
  
      vop_found= pc->frame_start_found;
      state= pc->state;
  
      i=0;
      if(!vop_found){
          for(i=0; i<buf_size; i++){
              state= (state<<8) | buf[i];
              if(state == 0x1B6){
                  i++;
                  vop_found=1;
                  break;
              }
          }
      }
  
      if(vop_found){
          /* EOF considered as end of frame */
          if (buf_size == 0)
              return 0;
          for(; i<buf_size; i++){
              state= (state<<8) | buf[i];
              if((state&0xFFFFFF00) == 0x100){
                  pc->frame_start_found=0;
                  pc->state=-1;
                  return i-3;
              }
          }
      }
      pc->frame_start_found= vop_found;
      pc->state= state;
      return END_NOT_FOUND;
  }
  
  /* XXX: make it use less memory */
  static int av_mpeg4_decode_header(AVCodecParserContext *s1,
                                    AVCodecContext *avctx,
                                    const uint8_t *buf, int buf_size)
  {
      ParseContext1 *pc = s1->priv_data;
      MpegEncContext *s = pc->enc;
      GetBitContext gb1, *gb = &gb1;
      int ret;
  
      s->avctx = avctx;
      s->current_picture_ptr = &s->current_picture;
  
      if (avctx->extradata_size && pc->first_picture){
          init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);
          ret = ff_mpeg4_decode_picture_header(s, gb);
      }
  
      init_get_bits(gb, buf, 8 * buf_size);
      ret = ff_mpeg4_decode_picture_header(s, gb);
      if (s->width) {
          avcodec_set_dimensions(avctx, s->width, s->height);
      }
      s1->pict_type= s->pict_type;
      pc->first_picture = 0;
      return ret;
  }
  
  static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
  {
      ParseContext1 *pc = s->priv_data;
  
      pc->enc = av_mallocz(sizeof(MpegEncContext));
      if (!pc->enc)
          return -1;
      pc->first_picture = 1;
      return 0;
  }
  
  static int mpeg4video_parse(AVCodecParserContext *s,
                             AVCodecContext *avctx,
                             const uint8_t **poutbuf, int *poutbuf_size,
                             const uint8_t *buf, int buf_size)
  {
      ParseContext *pc = s->priv_data;
      int next;
  
      if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
          next= buf_size;
      }else{
          next= ff_mpeg4_find_frame_end(pc, buf, buf_size);
  
          if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
              *poutbuf = NULL;
              *poutbuf_size = 0;
              return buf_size;
          }
      }
      av_mpeg4_decode_header(s, avctx, buf, buf_size);
  
      *poutbuf = buf;
      *poutbuf_size = buf_size;
      return next;
  }
  
  
  AVCodecParser mpeg4video_parser = {
      { CODEC_ID_MPEG4 },
      sizeof(ParseContext1),
      mpeg4video_parse_init,
      mpeg4video_parse,
      ff_parse1_close,
      ff_mpeg4video_split,
  };
  