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