1
2 /*
3 * gus_vol.c - Compute volume for GUS.
4 *
5 *
6 * Copyright (C) by Hannu Savolainen 1993-1997
7 *
8 * OSS/Free for Linux is distributed under the GNU GENERAL PUBLIC LICENSE (GPL)
9 * Version 2 (June 1991). See the "COPYING" file distributed with this software
10 * for more info.
11 */
12 #include "sound_config.h"
13
14 #include "gus.h"
15 #include "gus_linearvol.h"
16
17 #define GUS_VOLUME gus_wave_volume
18
19
20 extern int gus_wave_volume;
21
22 /*
23 * Calculate gus volume from note velocity, main volume, expression, and
24 * intrinsic patch volume given in patch library. Expression is multiplied
25 * in, so it emphasizes differences in note velocity, while main volume is
26 * added in -- I don't know whether this is right, but it seems reasonable to
27 * me. (In the previous stage, main volume controller messages were changed
28 * to expression controller messages, if they were found to be used for
29 * dynamic volume adjustments, so here, main volume can be assumed to be
30 * constant throughout a song.)
31 *
32 * Intrinsic patch volume is added in, but if over 64 is also multiplied in, so
33 * we can give a big boost to very weak voices like nylon guitar and the
34 * basses. The normal value is 64. Strings are assigned lower values.
35 */
36
37 unsigned short gus_adagio_vol(int vel, int mainv, int xpn, int voicev)
38 {
39 int i, m, n, x;
40
41
42 /*
43 * A voice volume of 64 is considered neutral, so adjust the main volume if
44 * something other than this neutral value was assigned in the patch
45 * library.
46 */
47 x = 256 + 6 * (voicev - 64);
48
49 /*
50 * Boost expression by voice volume above neutral.
51 */
52
53 if (voicev > 65)
54 xpn += voicev - 64;
55 xpn += (voicev - 64) / 2;
56
57 /*
58 * Combine multiplicative and level components.
59 */
60 x = vel * xpn * 6 + (voicev / 4) * x;
61
62 #ifdef GUS_VOLUME
63 /*
64 * Further adjustment by installation-specific master volume control
65 * (default 60).
66 */
67 x = (x * GUS_VOLUME * GUS_VOLUME) / 10000;
68 #endif
69
70 #ifdef GUS_USE_CHN_MAIN_VOLUME
71 /*
72 * Experimental support for the channel main volume
73 */
74
75 mainv = (mainv / 2) + 64; /* Scale to 64 to 127 */
76 x = (x * mainv * mainv) / 16384;
77 #endif
78
79 if (x < 2)
80 return (0);
81 else if (x >= 65535)
82 return ((15 << 8) | 255);
83
84 /*
85 * Convert to GUS's logarithmic form with 4 bit exponent i and 8 bit
86 * mantissa m.
87 */
88
89 n = x;
90 i = 7;
91 if (n < 128)
92 {
93 while (i > 0 && n < (1 << i))
94 i--;
95 }
96 else
97 {
98 while (n > 255)
99 {
100 n >>= 1;
101 i++;
102 }
103 }
104 /*
105 * Mantissa is part of linear volume not expressed in exponent. (This is
106 * not quite like real logs -- I wonder if it's right.)
107 */
108 m = x - (1 << i);
109
110 /*
111 * Adjust mantissa to 8 bits.
112 */
113 if (m > 0)
114 {
115 if (i > 8)
116 m >>= i - 8;
117 else if (i < 8)
118 m <<= 8 - i;
119 }
120 return ((i << 8) + m);
121 }
122
123 /*
124 * Volume-values are interpreted as linear values. Volume is based on the
125 * value supplied with SEQ_START_NOTE(), channel main volume (if compiled in)
126 * and the volume set by the mixer-device (default 60%).
127 */
128
129 unsigned short gus_linear_vol(int vol, int mainvol)
130 {
131 int mixer_mainvol;
132
133 if (vol <= 0)
134 vol = 0;
135 else if (vol >= 127)
136 vol = 127;
137
138 #ifdef GUS_VOLUME
139 mixer_mainvol = GUS_VOLUME;
140 #else
141 mixer_mainvol = 100;
142 #endif
143
144 #ifdef GUS_USE_CHN_MAIN_VOLUME
145 if (mainvol <= 0)
146 mainvol = 0;
147 else if (mainvol >= 127)
148 mainvol = 127;
149 #else
150 mainvol = 127;
151 #endif
152 return gus_linearvol[(((vol * mainvol) / 127) * mixer_mainvol) / 100];
153 }
154
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