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Diffstat (limited to 'sys/i386/isa/sound/gus_vol.c')
-rw-r--r-- | sys/i386/isa/sound/gus_vol.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/sys/i386/isa/sound/gus_vol.c b/sys/i386/isa/sound/gus_vol.c new file mode 100644 index 0000000..fc66618 --- /dev/null +++ b/sys/i386/isa/sound/gus_vol.c @@ -0,0 +1,138 @@ +/* + * 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 |