drivers/sound/gus

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

DEFINITIONS
