libavcodec/mpegaudio.c

   1 /*
   2  * MPEG Audio common code
   3  * Copyright (c) 2001, 2002 Fabrice Bellard.
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file mpegaudio.c
  24  * MPEG Audio common code.
  25  */
  26
  27 #include "mpegaudio.h"
  28
  29
  30 /* bitrate is in kb/s */
  31 int ff_mpa_l2_select_table(int bitrate, int nb_channels, int freq, int lsf)
  32 {
  33     int ch_bitrate, table;
  34
  35     ch_bitrate = bitrate / nb_channels;
  36     if (!lsf) {
  37         if ((freq == 48000 && ch_bitrate >= 56) ||
  38             (ch_bitrate >= 56 && ch_bitrate <= 80))
  39             table = 0;
  40         else if (freq != 48000 && ch_bitrate >= 96)
  41             table = 1;
  42         else if (freq != 32000 && ch_bitrate <= 48)
  43             table = 2;
  44         else
  45             table = 3;
  46     } else {
  47         table = 4;
  48     }
  49     return table;
  50 }