musix 0.3.5

Music player library for esoteric audio formats (music from C64,Amiga etc)
Documentation 
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/*
 * @file    ym_atarist_table.c
 * @brief   YM-2149 emulator - Atari ST Volume Table
 * @author  http://sourceforge.net/users/benjihan
 *
 * Copyright (C) 1998-2011 Benjamin Gerard
 *
 * Time-stamp: <2011-10-27 11:54:14 ben>
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.
 *
 * If not, see <http://www.gnu.org/licenses/>.
 *
 */

/* Table of 4 bit D/A output level for 1 channel.*/
static const u16 volumetable_original[32 * 32 * 32] =
# include "ymout2k9.h"
  ;

/* Create a non-linear 3 channels 5 bit per channels DAC table.
 */
static void
create_table(s16 * out, uint_t level, const char * name)
{
  int h;

  if (!level) {
    for (h=0; h<32*32*32; ++h) {
      out[h] = 0;
    }
  } else {
    for (h=0; h<32*32*32; ++h) {
      out[h] = volumetable_original[h];
    }
  }

  if (level) {
    const int min = ((u16*)out)[0x0000];
    const int max = ((u16*)out)[0x7fff];
    const int div = max-min ? max-min : 1;
    const int mid = ( level + 1 ) >> 1;

    TRACE68(ym_cat,
            "ym-2149: creating %s -- min:%d max:%d div:%d mid:%d\n",
            name, min, max, div, mid);

    assert(level < 65536u);
    assert(max > min);

    for (h=0; h<32*32*32; ++h) {
      int tmp = ((u16*)out)[h], res;
      assert(tmp >= min);
      assert(tmp <= max);
      res = (tmp-min) * level / div - mid;
      out[h] = res;
    }
  }
  msg68_notice("ym-2149: volume model -- *%s* -- [%d..%d]\n",
               name, out[0], out[0x7FFF]);
}

/* Create a non-linear 3 channels 5 bit per channels DAC table.
 */
void ym_create_5bit_atarist_table(s16 * out, unsigned int level)
{
  create_table(out, level,"atarist-5bit-2k9");
}

/* Create a non-linear 3 channels 4 bit per channels DAC table.
 */
void ym_create_4bit_atarist_table(s16 * out, unsigned int level)
{
  create_table(out, level,"atarist-4bit");
}