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ffmpeg-4.2.2/libavcodec/amr.h 2.18 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * Shared functions between AMR codecs
   *
   * Copyright (c) 2010 Marcelo Galvao Povoa
   *
   * 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
   */
  
  #ifndef AVCODEC_AMR_H
  #define AVCODEC_AMR_H
  
  #include <string.h>
  
  #include "avcodec.h"
  
  #ifdef AMR_USE_16BIT_TABLES
  typedef uint16_t R_TABLE_TYPE;
  #else
  typedef uint8_t R_TABLE_TYPE;
  #endif
  
  /**
   * Fill the frame structure variables from bitstream by parsing the
   * given reordering table that uses the following format:
   *
   * Each field (16 bits) in the AMR Frame is stored as:
   * - one byte for the number of bits in the field
   * - one byte for the field index
   * - then, one byte for each bit of the field (from most-significant to least)
   *         of the position of that bit in the AMR frame.
   *
   * @param out pointer to the frame struct
   * @param size the size in bytes of the frame struct
   * @param data input bitstream after the frame header
   * @param ord_table the reordering table as above
   */
  static inline void ff_amr_bit_reorder(uint16_t *out, int size,
                                        const uint8_t *data,
                                        const R_TABLE_TYPE *ord_table)
  {
      int field_size;
  
      memset(out, 0, size);
      while ((field_size = *ord_table++)) {
          int field = 0;
          int field_offset = *ord_table++;
          while (field_size--) {
             int bit = *ord_table++;
             field <<= 1;
             field |= data[bit >> 3] >> (bit & 7) & 1;
          }
          out[field_offset >> 1] = field;
      }
  }
  
  #endif /* AVCODEC_AMR_H */