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/*

 * gus_vol.c - Compute volume for GUS.

 */

/*

 * Copyright (C) by Hannu Savolainen 1993-1996

 *

 * USS/Lite 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 <linux/config.h>

#include "sound_config.h"

#ifdef CONFIG_GUS

#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];

}

#endif