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ffmpeg-4.2.2/libavcodec/vp56rac.c 1.75 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * VP5/6/8 decoder
   * Copyright (c) 2010 Fiona Glaser <fiona@x264.com>
   *
   * 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 "libavutil/common.h"
  #include "vp56.h"
  
  const uint8_t ff_vp56_norm_shift[256]= {
   8,7,6,6,5,5,5,5,4,4,4,4,4,4,4,4,
   3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
   2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
   2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
   1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
   1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
   1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
   1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
   0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
   0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
   0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
   0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  };
  
  int ff_vp56_init_range_decoder(VP56RangeCoder *c, const uint8_t *buf, int buf_size)
  {
      c->high = 255;
      c->bits = -16;
      c->buffer = buf;
      c->end = buf + buf_size;
      c->end_reached = 0;
      if (buf_size < 1)
          return AVERROR_INVALIDDATA;
      c->code_word = bytestream_get_be24(&c->buffer);
      return 0;
  }