freebsd/sys/i386/isa/sound/gus_vol.c

/*
 * gus_vol.c - Compute volume for GUS.
 * 
 * Greg Lee 1993.
 */
#include <i386/isa/sound/sound_config.h>

#ifdef CONFIG_GUS
#include <i386/isa/sound/gus_linearvol.h>

#define GUS_VOLUME	gus_wave_volume


extern int      gus_wave_volume;
unsigned short  gus_adagio_vol(int vel, int mainv, int xpn, int voicev);
unsigned short  gus_linear_vol(int vol, int mainvol);

/*
 * 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 60).
     */
    x = (x * GUS_VOLUME * GUS_VOLUME) / 10000;
#endif

#ifdef GUS_USE_CHN_MAIN_VOLUME
    /*
     * Experimental support for the channel main volume
     */

    mainv = (mainv / 2) + 64;	/* Scale to 64 to 127 */
    x = (x * mainv * mainv) / 16384;
#endif

    if (x < 2)
	return (0);
    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;
    }
    return ((i << 8) + m);
}

/*
 * Volume-values are interpreted as linear values. Volume is based on the
 * value supplied with SEQ_START_NOTE(), channel main volume (if compiled in)
 * and the volume set by the mixer-device (default 60%).
 */

unsigned short
gus_linear_vol(int vol, int mainvol)
{
    int             mixer_mainvol;

    RANGE (vol, 0, 127) ;

#ifdef GUS_VOLUME
    mixer_mainvol = GUS_VOLUME;
#else
    mixer_mainvol = 100;
#endif

#ifdef GUS_USE_CHN_MAIN_VOLUME
    RANGE (mainvol, 0, 127);
#else
    mainvol = 127;
#endif

    return gus_linearvol[(((vol * mainvol) / 127) * mixer_mainvol) / 100];
}

#endif