102 lines
2.4 KiB
C
102 lines
2.4 KiB
C
|
/*
|
||
|
|
* gus_vol.c - Compute volume for GUS.
|
||
|
|
*
|
||
|
|
* Greg Lee 1993.
|
||
|
|
*/
|
||
|
|
#include "sound_config.h"
|
||
|
|
#ifndef EXCLUDE_GUS
|
||
|
|
|
||
|
|
#define GUS_VOLUME gus_wave_volume
|
||
|
|
|
||
|
|
|
||
|
|
extern int gus_wave_volume;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Calculate gus volume from note velocity, main volume, expression, and
|
||
|
|
* intrinsic patch volume given in patch library. Expression is multiplied
|
||
|
|
* in, so it emphasizes differences in note velocity, while main volume is
|
||
|
|
* added in -- I don't know whether this is right, but it seems reasonable to
|
||
|
|
* me. (In the previous stage, main volume controller messages were changed
|
||
|
|
* to expression controller messages, if they were found to be used for
|
||
|
|
* dynamic volume adjustments, so here, main volume can be assumed to be
|
||
|
|
* constant throughout a song.)
|
||
|
|
*
|
||
|
|
* Intrinsic patch volume is added in, but if over 64 is also multiplied in, so
|
||
|
|
* we can give a big boost to very weak voices like nylon guitar and the
|
||
|
|
* basses. The normal value is 64. Strings are assigned lower values.
|
||
|
|
*/
|
||
|
|
unsigned short
|
||
|
|
gus_adagio_vol (int vel, int mainv, int xpn, int voicev)
|
||
|
|
{
|
||
|
|
int i, m, n, x;
|
||
|
|
|
||
|
|
|
||
|
|
/*
|
||
|
|
* A voice volume of 64 is considered neutral, so adjust the main volume if
|
||
|
|
* something other than this neutral value was assigned in the patch
|
||
|
|
* library.
|
||
|
|
*/
|
||
|
|
x = 256 + 6 * (voicev - 64);
|
||
|
|
|
||
|
|
/* Boost expression by voice volume above neutral. */
|
||
|
|
if (voicev > 65)
|
||
|
|
xpn += voicev - 64;
|
||
|
|
xpn += (voicev - 64) / 2;
|
||
|
|
|
||
|
|
/* Combine multiplicative and level components. */
|
||
|
|
x = vel * xpn * 6 + (voicev / 4) * x;
|
||
|
|
|
||
|
|
#ifdef GUS_VOLUME
|
||
|
|
/*
|
||
|
|
* Further adjustment by installation-specific master volume control
|
||
|
|
* (default 50).
|
||
|
|
*/
|
||
|
|
x = (x * GUS_VOLUME * GUS_VOLUME) / 10000;
|
||
|
|
#endif
|
||
|
|
|
||
|
|
if (x < (1 << 11))
|
||
|
|
return (11 << 8);
|
||
|
|
else if (x >= 65535)
|
||
|
|
return ((15 << 8) | 255);
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Convert to gus's logarithmic form with 4 bit exponent i and 8 bit
|
||
|
|
* mantissa m.
|
||
|
|
*/
|
||
|
|
n = x;
|
||
|
|
i = 7;
|
||
|
|
if (n < 128)
|
||
|
|
{
|
||
|
|
while (i > 0 && n < (1 << i))
|
||
|
|
i--;
|
||
|
|
}
|
||
|
|
else
|
||
|
|
while (n > 255)
|
||
|
|
{
|
||
|
|
n >>= 1;
|
||
|
|
i++;
|
||
|
|
}
|
||
|
|
/*
|
||
|
|
* Mantissa is part of linear volume not expressed in exponent. (This is
|
||
|
|
* not quite like real logs -- I wonder if it's right.)
|
||
|
|
*/
|
||
|
|
m = x - (1 << i);
|
||
|
|
|
||
|
|
/* Adjust mantissa to 8 bits. */
|
||
|
|
if (m > 0)
|
||
|
|
{
|
||
|
|
if (i > 8)
|
||
|
|
m >>= i - 8;
|
||
|
|
else if (i < 8)
|
||
|
|
m <<= 8 - i;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* low volumes give occasional sour notes */
|
||
|
|
if (i < 11)
|
||
|
|
return (11 << 8);
|
||
|
|
|
||
|
|
return ((i << 8) + m);
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif
|