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151 lines
3.3 KiB
C
151 lines
3.3 KiB
C
/*
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* gus_vol.c - Compute volume for GUS.
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*
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* Greg Lee 1993.
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*/
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#include "sound_config.h"
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#ifndef EXCLUDE_GUS
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#include "gus_linearvol.h"
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extern unsigned short gus_adagio_vol (int vel, int mainv, int xpn, int voicev);
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extern unsigned short gus_linear_vol (int vol, int mainvol);
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#define GUS_VOLUME gus_wave_volume
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extern int gus_wave_volume;
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/*
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* Calculate gus volume from note velocity, main volume, expression, and
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* intrinsic patch volume given in patch library. Expression is multiplied
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* in, so it emphasizes differences in note velocity, while main volume is
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* added in -- I don't know whether this is right, but it seems reasonable to
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* me. (In the previous stage, main volume controller messages were changed
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* to expression controller messages, if they were found to be used for
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* dynamic volume adjustments, so here, main volume can be assumed to be
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* constant throughout a song.)
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*
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* Intrinsic patch volume is added in, but if over 64 is also multiplied in, so
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* we can give a big boost to very weak voices like nylon guitar and the
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* basses. The normal value is 64. Strings are assigned lower values.
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*/
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unsigned short
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gus_adagio_vol (int vel, int mainv, int xpn, int voicev)
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{
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int i, m, n, x;
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/*
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* A voice volume of 64 is considered neutral, so adjust the main volume if
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* something other than this neutral value was assigned in the patch
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* library.
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*/
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x = 256 + 6 * (voicev - 64);
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/*
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* Boost expression by voice volume above neutral.
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*/
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if (voicev > 65)
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xpn += voicev - 64;
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xpn += (voicev - 64) / 2;
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/*
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* Combine multiplicative and level components.
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*/
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x = vel * xpn * 6 + (voicev / 4) * x;
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#ifdef GUS_VOLUME
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/*
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* Further adjustment by installation-specific master volume control
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* (default 60).
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*/
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x = (x * GUS_VOLUME * GUS_VOLUME) / 10000;
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#endif
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#ifdef GUS_USE_CHN_MAIN_VOLUME
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/*
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* Experimental support for the channel main volume
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*/
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mainv = (mainv / 2) + 64; /* Scale to 64 to 127 */
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x = (x * mainv * mainv) / 16384;
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#endif
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if (x < 2)
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return (0);
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else if (x >= 65535)
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return ((15 << 8) | 255);
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/*
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* Convert to gus's logarithmic form with 4 bit exponent i and 8 bit
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* mantissa m.
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*/
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n = x;
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i = 7;
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if (n < 128)
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{
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while (i > 0 && n < (1 << i))
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i--;
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}
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else
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while (n > 255)
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{
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n >>= 1;
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i++;
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}
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/*
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* Mantissa is part of linear volume not expressed in exponent. (This is
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* not quite like real logs -- I wonder if it's right.)
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*/
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m = x - (1 << i);
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/*
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* Adjust mantissa to 8 bits.
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*/
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if (m > 0)
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{
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if (i > 8)
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m >>= i - 8;
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else if (i < 8)
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m <<= 8 - i;
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}
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return ((i << 8) + m);
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}
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/*
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* Volume-values are interpreted as linear values. Volume is based on the
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* value supplied with SEQ_START_NOTE(), channel main volume (if compiled in)
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* and the volume set by the mixer-device (default 60%).
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*/
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unsigned short
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gus_linear_vol (int vol, int mainvol)
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{
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int mixer_mainvol;
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if (vol <= 0)
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vol = 0;
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else if (vol >= 127)
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vol = 127;
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#ifdef GUS_VOLUME
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mixer_mainvol = GUS_VOLUME;
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#else
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mixer_mainvol = 100;
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#endif
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#ifdef GUS_USE_CHN_MAIN_VOLUME
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if (mainvol <= 0)
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mainvol = 0;
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else if (mainvol >= 127)
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mainvol = 127;
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#else
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mainvol = 128;
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#endif
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return gus_linearvol[(((vol * mainvol) / 128) * mixer_mainvol) / 100];
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}
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#endif
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