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ffmpeg-4.2.2/libavcodec/cavs_parser.c 3.04 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * Chinese AVS video (AVS1-P2, JiZhun profile) parser.
   * Copyright (c) 2006  Stefan Gehrer <stefan.gehrer@gmx.de>
   *
   * 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
   */
  
  /**
   * @file
   * Chinese AVS video (AVS1-P2, JiZhun profile) parser
   * @author Stefan Gehrer <stefan.gehrer@gmx.de>
   */
  
  #include "parser.h"
  #include "cavs.h"
  
  
  /**
   * Find the end of the current frame in the bitstream.
   * @return the position of the first byte of the next frame, or -1
   */
  static int cavs_find_frame_end(ParseContext *pc, const uint8_t *buf,
                                 int buf_size) {
      int pic_found, i;
      uint32_t state;
  
      pic_found= pc->frame_start_found;
      state= pc->state;
  
      i=0;
      if(!pic_found){
          for(i=0; i<buf_size; i++){
              state= (state<<8) | buf[i];
              if(state == PIC_I_START_CODE || state == PIC_PB_START_CODE){
                  i++;
                  pic_found=1;
                  break;
              }
          }
      }
  
      if(pic_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){
                  if(state > SLICE_MAX_START_CODE){
                      pc->frame_start_found=0;
                      pc->state=-1;
                      return i-3;
                  }
              }
          }
      }
      pc->frame_start_found= pic_found;
      pc->state= state;
      return END_NOT_FOUND;
  }
  
  static int cavsvideo_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= cavs_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;
          }
      }
      *poutbuf = buf;
      *poutbuf_size = buf_size;
      return next;
  }
  
  AVCodecParser ff_cavsvideo_parser = {
      .codec_ids      = { AV_CODEC_ID_CAVS },
      .priv_data_size = sizeof(ParseContext),
      .parser_parse   = cavsvideo_parse,
      .parser_close   = ff_parse_close,
      .split          = ff_mpeg4video_split,
  };