sound/oss/gus_vol.c

   1
   2 /*
   3  * gus_vol.c - Compute volume for GUS.
   4  *
   5  *
   6  * Copyright (C) by Hannu Savolainen 1993-1997
   7  *
   8  * OSS/Free for Linux is distributed under the GNU GENERAL PUBLIC LICENSE (GPL)
   9  * Version 2 (June 1991). See the "COPYING" file distributed with this software
  10  * for more info.
  11  */
  12 #include "sound_config.h"
  13
  14 #include "gus.h"
  15 #include "gus_linearvol.h"
  16
  17 #define GUS_VOLUME      gus_wave_volume
  18
  19
  20 extern int      gus_wave_volume;
  21
  22 /*
  23  * Calculate gus volume from note velocity, main volume, expression, and
  24  * intrinsic patch volume given in patch library.  Expression is multiplied
  25  * in, so it emphasizes differences in note velocity, while main volume is
  26  * added in -- I don't know whether this is right, but it seems reasonable to
  27  * me.  (In the previous stage, main volume controller messages were changed
  28  * to expression controller messages, if they were found to be used for
  29  * dynamic volume adjustments, so here, main volume can be assumed to be
  30  * constant throughout a song.)
  31  *
  32  * Intrinsic patch volume is added in, but if over 64 is also multiplied in, so
  33  * we can give a big boost to very weak voices like nylon guitar and the
  34  * basses.  The normal value is 64.  Strings are assigned lower values.
  35  */
  36
  37 unsigned short gus_adagio_vol(int vel, int mainv, int xpn, int voicev)
  38 {
  39         int i, m, n, x;
  40
  41
  42         /*
  43          * A voice volume of 64 is considered neutral, so adjust the main volume if
  44          * something other than this neutral value was assigned in the patch
  45          * library.
  46          */
  47         x = 256 + 6 * (voicev - 64);
  48
  49         /*
  50          * Boost expression by voice volume above neutral.
  51          */
  52
  53         if (voicev > 65)
  54                 xpn += voicev - 64;
  55         xpn += (voicev - 64) / 2;
  56
  57         /*
  58          * Combine multiplicative and level components.
  59          */
  60         x = vel * xpn * 6 + (voicev / 4) * x;
  61
  62 #ifdef GUS_VOLUME
  63         /*
  64          * Further adjustment by installation-specific master volume control
  65          * (default 60).
  66          */
  67         x = (x * GUS_VOLUME * GUS_VOLUME) / 10000;
  68 #endif
  69
  70 #ifdef GUS_USE_CHN_MAIN_VOLUME
  71         /*
  72          * Experimental support for the channel main volume
  73          */
  74
  75         mainv = (mainv / 2) + 64;       /* Scale to 64 to 127 */
  76         x = (x * mainv * mainv) / 16384;
  77 #endif
  78
  79         if (x < 2)
  80                 return (0);
  81         else if (x >= 65535)
  82                 return ((15 << 8) | 255);
  83
  84         /*
  85          * Convert to GUS's logarithmic form with 4 bit exponent i and 8 bit
  86          * mantissa m.
  87          */
  88
  89         n = x;
  90         i = 7;
  91         if (n < 128)
  92         {
  93                   while (i > 0 && n < (1 << i))
  94                           i--;
  95         }
  96         else
  97         {
  98                 while (n > 255)
  99                 {
 100                           n >>= 1;
 101                           i++;
 102                 }
 103         }
 104         /*
 105          * Mantissa is part of linear volume not expressed in exponent.  (This is
 106          * not quite like real logs -- I wonder if it's right.)
 107          */
 108         m = x - (1 << i);
 109
 110         /*
 111          * Adjust mantissa to 8 bits.
 112          */
 113         if (m > 0)
 114         {
 115                 if (i > 8)
 116                         m >>= i - 8;
 117                 else if (i < 8)
 118                         m <<= 8 - i;
 119         }
 120         return ((i << 8) + m);
 121 }
 122
 123 /*
 124  * Volume-values are interpreted as linear values. Volume is based on the
 125  * value supplied with SEQ_START_NOTE(), channel main volume (if compiled in)
 126  * and the volume set by the mixer-device (default 60%).
 127  */
 128
 129 unsigned short gus_linear_vol(int vol, int mainvol)
 130 {
 131         int mixer_mainvol;
 132
 133         if (vol <= 0)
 134                 vol = 0;
 135         else if (vol >= 127)
 136                 vol = 127;
 137
 138 #ifdef GUS_VOLUME
 139         mixer_mainvol = GUS_VOLUME;
 140 #else
 141         mixer_mainvol = 100;
 142 #endif
 143
 144 #ifdef GUS_USE_CHN_MAIN_VOLUME
 145         if (mainvol <= 0)
 146                 mainvol = 0;
 147         else if (mainvol >= 127)
 148                 mainvol = 127;
 149 #else
 150         mainvol = 127;
 151 #endif
 152         return gus_linearvol[(((vol * mainvol) / 127) * mixer_mainvol) / 100];
 153 }