gus_vol.c

iis s3c2410-uda1341语音系统的 开发

/*
 * gus_vol.c - Compute volume for GUS.
 *
 *
 * Copyright (C) by Hannu Savolainen 1993-1997
 *
 * OSS/Free for Linux is distributed under the GNU GENERAL PUBLIC LICENSE (GPL)
 * Version 2 (June 1991). See the "COPYING" file distributed with this software
 * for more info.
 */
#include "sound_config.h"

#include "gus.h"
#include "gus_linearvol.h"

#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 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;

	if (vol <= 0)
		vol = 0;
	else if (vol >= 127)
		vol = 127;

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

#ifdef GUS_USE_CHN_MAIN_VOLUME
	if (mainvol <= 0)
		mainvol = 0;
	else if (mainvol >= 127)
		mainvol = 127;
#else
	mainvol = 127;
#endif
	return gus_linearvol[(((vol * mainvol) / 127) * mixer_mainvol) / 100];
}