1 files changed, 153 insertions, 0 deletions
diff --git a/sound/oss/gus_vol.c b/sound/oss/gus_vol.c
new file mode 100644
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+
+/*
+ * 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];
+}