aboutsummaryrefslogtreecommitdiff
path: root/sound/oss/gus_vol.c
blob: 6ae6924e16475d1eb2c4f2003aa7ba1bd3f771f3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153

/*
 * 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];
}