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ffmpeg-4.2.2/libavcodec/mpegaudio.c 1.43 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * MPEG Audio common code
   * Copyright (c) 2001, 2002 Fabrice Bellard
   *
   * 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
   * MPEG Audio common code.
   */
  
  #include "mpegaudio.h"
  
  
  /* bitrate is in kb/s */
  int ff_mpa_l2_select_table(int bitrate, int nb_channels, int freq, int lsf)
  {
      int ch_bitrate, table;
  
      ch_bitrate = bitrate / nb_channels;
      if (!lsf) {
          if ((freq == 48000 && ch_bitrate >= 56) ||
              (ch_bitrate >= 56 && ch_bitrate <= 80))
              table = 0;
          else if (freq != 48000 && ch_bitrate >= 96)
              table = 1;
          else if (freq != 32000 && ch_bitrate <= 48)
              table = 2;
          else
              table = 3;
      } else {
          table = 4;
      }
      return table;
  }