--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/decoders/timidity/mix.c	Fri Jan 04 06:49:49 2002 +0000
@@ -0,0 +1,573 @@
+/*
+
+    TiMidity -- Experimental MIDI to WAVE converter
+    Copyright (C) 1995 Tuukka Toivonen <toivonen@clinet.fi>
+
+    Suddenly, you realize that this program is free software; you get
+    an overwhelming urge to redistribute it and/or modify it under the
+    terms of the GNU General Public License as published by the Free
+    Software Foundation; either version 2 of the License, or (at your
+    option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received another copy of the GNU General Public
+    License along with this program; if not, write to the Free
+    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+    I bet they'll be amazed.
+
+    mix.c */
+
+#if HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "SDL_sound.h"
+
+#define __SDL_SOUND_INTERNAL__
+#include "SDL_sound_internal.h"
+
+#include "timidity.h"
+#include "options.h"
+#include "instrum.h"
+#include "playmidi.h"
+#include "output.h"
+#include "tables.h"
+#include "resample.h"
+#include "mix.h"
+
+/* Returns 1 if envelope runs out */
+int recompute_envelope(MidiSong *song, int v)
+{
+  int stage;
+
+  stage = song->voice[v].envelope_stage;
+
+  if (stage>5)
+    {
+      /* Envelope ran out. */
+      song->voice[v].status = VOICE_FREE;
+      return 1;
+    }
+
+  if (song->voice[v].sample->modes & MODES_ENVELOPE)
+    {
+      if (song->voice[v].status==VOICE_ON || song->voice[v].status==VOICE_SUSTAINED)
+	{
+	  if (stage>2)
+	    {
+	      /* Freeze envelope until note turns off. Trumpets want this. */
+	      song->voice[v].envelope_increment=0;
+	      return 0;
+	    }
+	}
+    }
+  song->voice[v].envelope_stage=stage+1;
+
+  if (song->voice[v].envelope_volume==song->voice[v].sample->envelope_offset[stage])
+    return recompute_envelope(song, v);
+  song->voice[v].envelope_target = song->voice[v].sample->envelope_offset[stage];
+  song->voice[v].envelope_increment = song->voice[v].sample->envelope_rate[stage];
+  if (song->voice[v].envelope_target < song->voice[v].envelope_volume)
+    song->voice[v].envelope_increment = -song->voice[v].envelope_increment;
+  return 0;
+}
+
+void apply_envelope_to_amp(MidiSong *song, int v)
+{
+  float lamp = song->voice[v].left_amp, ramp;
+  Sint32 la,ra;
+  if (song->voice[v].panned == PANNED_MYSTERY)
+    {
+      ramp = song->voice[v].right_amp;
+      if (song->voice[v].tremolo_phase_increment)
+	{
+	  lamp *= song->voice[v].tremolo_volume;
+	  ramp *= song->voice[v].tremolo_volume;
+	}
+      if (song->voice[v].sample->modes & MODES_ENVELOPE)
+	{
+	  lamp *= (float)vol_table[song->voice[v].envelope_volume>>23];
+	  ramp *= (float)vol_table[song->voice[v].envelope_volume>>23];
+	}
+
+      la = (Sint32)FSCALE(lamp,AMP_BITS);
+      
+      if (la>MAX_AMP_VALUE)
+	la=MAX_AMP_VALUE;
+
+      ra = (Sint32)FSCALE(ramp,AMP_BITS);
+      if (ra>MAX_AMP_VALUE)
+	ra=MAX_AMP_VALUE;
+      
+      song->voice[v].left_mix = la;
+      song->voice[v].right_mix = ra;
+    }
+  else
+    {
+      if (song->voice[v].tremolo_phase_increment)
+	lamp *= song->voice[v].tremolo_volume;
+      if (song->voice[v].sample->modes & MODES_ENVELOPE)
+	lamp *= (float)vol_table[song->voice[v].envelope_volume>>23];
+
+      la = (Sint32)FSCALE(lamp,AMP_BITS);
+
+      if (la>MAX_AMP_VALUE)
+	la=MAX_AMP_VALUE;
+
+      song->voice[v].left_mix = la;
+    }
+}
+
+static int update_envelope(MidiSong *song, int v)
+{
+  song->voice[v].envelope_volume += song->voice[v].envelope_increment;
+  /* Why is there no ^^ operator?? */
+  if (((song->voice[v].envelope_increment < 0) &&
+       (song->voice[v].envelope_volume <= song->voice[v].envelope_target)) ||
+      ((song->voice[v].envelope_increment > 0) &&
+	   (song->voice[v].envelope_volume >= song->voice[v].envelope_target)))
+    {
+      song->voice[v].envelope_volume = song->voice[v].envelope_target;
+      if (recompute_envelope(song, v))
+	return 1;
+    }
+  return 0;
+}
+
+static void update_tremolo(MidiSong *song, int v)
+{
+  Sint32 depth = song->voice[v].sample->tremolo_depth << 7;
+
+  if (song->voice[v].tremolo_sweep)
+    {
+      /* Update sweep position */
+
+      song->voice[v].tremolo_sweep_position += song->voice[v].tremolo_sweep;
+      if (song->voice[v].tremolo_sweep_position >= (1 << SWEEP_SHIFT))
+	song->voice[v].tremolo_sweep=0; /* Swept to max amplitude */
+      else
+	{
+	  /* Need to adjust depth */
+	  depth *= song->voice[v].tremolo_sweep_position;
+	  depth >>= SWEEP_SHIFT;
+	}
+    }
+
+  song->voice[v].tremolo_phase += song->voice[v].tremolo_phase_increment;
+
+  /* if (song->voice[v].tremolo_phase >= (SINE_CYCLE_LENGTH<<RATE_SHIFT))
+     song->voice[v].tremolo_phase -= SINE_CYCLE_LENGTH<<RATE_SHIFT;  */
+
+  song->voice[v].tremolo_volume = (float) 
+    (1.0 - FSCALENEG((sine(song->voice[v].tremolo_phase >> RATE_SHIFT) + 1.0)
+		    * depth * TREMOLO_AMPLITUDE_TUNING,
+		    17));
+
+  /* I'm not sure about the +1.0 there -- it makes tremoloed voices'
+     volumes on average the lower the higher the tremolo amplitude. */
+}
+
+/* Returns 1 if the note died */
+static int update_signal(MidiSong *song, int v)
+{
+  if (song->voice[v].envelope_increment && update_envelope(song, v))
+    return 1;
+
+  if (song->voice[v].tremolo_phase_increment)
+    update_tremolo(song, v);
+
+  apply_envelope_to_amp(song, v);
+  return 0;
+}
+
+#define MIXATION(a)	*lp++ += (a)*s;
+
+static void mix_mystery_signal(MidiSong *song, sample_t *sp, Sint32 *lp, int v,
+			       int count)
+{
+  Voice *vp = song->voice + v;
+  final_volume_t 
+    left=vp->left_mix, 
+    right=vp->right_mix;
+  int cc;
+  sample_t s;
+
+  if (!(cc = vp->control_counter))
+    {
+      cc = song->control_ratio;
+      if (update_signal(song, v))
+	return;	/* Envelope ran out */
+      left = vp->left_mix;
+      right = vp->right_mix;
+    }
+  
+  while (count)
+    if (cc < count)
+      {
+	count -= cc;
+	while (cc--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	    MIXATION(right);
+	  }
+	cc = song->control_ratio;
+	if (update_signal(song, v))
+	  return;	/* Envelope ran out */
+	left = vp->left_mix;
+	right = vp->right_mix;
+      }
+    else
+      {
+	vp->control_counter = cc - count;
+	while (count--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	    MIXATION(right);
+	  }
+	return;
+      }
+}
+
+static void mix_center_signal(MidiSong *song, sample_t *sp, Sint32 *lp, int v,
+			      int count)
+{
+  Voice *vp = song->voice + v;
+  final_volume_t 
+    left=vp->left_mix;
+  int cc;
+  sample_t s;
+
+  if (!(cc = vp->control_counter))
+    {
+      cc = song->control_ratio;
+      if (update_signal(song, v))
+	return;	/* Envelope ran out */
+      left = vp->left_mix;
+    }
+  
+  while (count)
+    if (cc < count)
+      {
+	count -= cc;
+	while (cc--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	    MIXATION(left);
+	  }
+	cc = song->control_ratio;
+	if (update_signal(song, v))
+	  return;	/* Envelope ran out */
+	left = vp->left_mix;
+      }
+    else
+      {
+	vp->control_counter = cc - count;
+	while (count--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	    MIXATION(left);
+	  }
+	return;
+      }
+}
+
+static void mix_single_signal(MidiSong *song, sample_t *sp, Sint32 *lp, int v,
+			      int count)
+{
+  Voice *vp = song->voice + v;
+  final_volume_t 
+    left=vp->left_mix;
+  int cc;
+  sample_t s;
+  
+  if (!(cc = vp->control_counter))
+    {
+      cc = song->control_ratio;
+      if (update_signal(song, v))
+	return;	/* Envelope ran out */
+      left = vp->left_mix;
+    }
+  
+  while (count)
+    if (cc < count)
+      {
+	count -= cc;
+	while (cc--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	    lp++;
+	  }
+	cc = song->control_ratio;
+	if (update_signal(song, v))
+	  return;	/* Envelope ran out */
+	left = vp->left_mix;
+      }
+    else
+      {
+	vp->control_counter = cc - count;
+	while (count--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	    lp++;
+	  }
+	return;
+      }
+}
+
+static void mix_mono_signal(MidiSong *song, sample_t *sp, Sint32 *lp, int v,
+			    int count)
+{
+  Voice *vp = song->voice + v;
+  final_volume_t 
+    left=vp->left_mix;
+  int cc;
+  sample_t s;
+  
+  if (!(cc = vp->control_counter))
+    {
+      cc = song->control_ratio;
+      if (update_signal(song, v))
+	return;	/* Envelope ran out */
+      left = vp->left_mix;
+    }
+  
+  while (count)
+    if (cc < count)
+      {
+	count -= cc;
+	while (cc--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	  }
+	cc = song->control_ratio;
+	if (update_signal(song, v))
+	  return;	/* Envelope ran out */
+	left = vp->left_mix;
+      }
+    else
+      {
+	vp->control_counter = cc - count;
+	while (count--)
+	  {
+	    s = *sp++;
+	    MIXATION(left);
+	  }
+	return;
+      }
+}
+
+static void mix_mystery(MidiSong *song, sample_t *sp, Sint32 *lp, int v, int count)
+{
+  final_volume_t 
+    left = song->voice[v].left_mix, 
+    right = song->voice[v].right_mix;
+  sample_t s;
+  
+  while (count--)
+    {
+      s = *sp++;
+      MIXATION(left);
+      MIXATION(right);
+    }
+}
+
+static void mix_center(MidiSong *song, sample_t *sp, Sint32 *lp, int v, int count)
+{
+  final_volume_t 
+    left = song->voice[v].left_mix;
+  sample_t s;
+  
+  while (count--)
+    {
+      s = *sp++;
+      MIXATION(left);
+      MIXATION(left);
+    }
+}
+
+static void mix_single(MidiSong *song, sample_t *sp, Sint32 *lp, int v, int count)
+{
+  final_volume_t 
+    left = song->voice[v].left_mix;
+  sample_t s;
+  
+  while (count--)
+    {
+      s = *sp++;
+      MIXATION(left);
+      lp++;
+    }
+}
+
+static void mix_mono(MidiSong *song, sample_t *sp, Sint32 *lp, int v, int count)
+{
+  final_volume_t 
+    left = song->voice[v].left_mix;
+  sample_t s;
+  
+  while (count--)
+    {
+      s = *sp++;
+      MIXATION(left);
+    }
+}
+
+/* Ramp a note out in c samples */
+static void ramp_out(MidiSong *song, sample_t *sp, Sint32 *lp, int v, Sint32 c)
+{
+
+  /* should be final_volume_t, but Uint8 gives trouble. */
+  Sint32 left, right, li, ri;
+
+  sample_t s=0; /* silly warning about uninitialized s */
+
+  /* Fix by James Caldwell */
+  if ( c == 0 ) c = 1;
+  
+  left=song->voice[v].left_mix;
+  li=-(left/c);
+  if (!li) li=-1;
+
+  /* printf("Ramping out: left=%d, c=%d, li=%d\n", left, c, li); */
+
+  if (!(song->encoding & PE_MONO))
+    {
+      if (song->voice[v].panned==PANNED_MYSTERY)
+	{
+	  right=song->voice[v].right_mix;
+	  ri=-(right/c);
+	  while (c--)
+	    {
+	      left += li;
+	      if (left<0)
+		left=0;
+	      right += ri;
+	      if (right<0)
+		right=0;
+	      s=*sp++;
+	      MIXATION(left);
+	      MIXATION(right);
+	    }
+	}
+      else if (song->voice[v].panned==PANNED_CENTER)
+	{
+	  while (c--)
+	    {
+	      left += li;
+	      if (left<0)
+		return;
+	      s=*sp++;	
+	      MIXATION(left);
+	      MIXATION(left);
+	    }
+	}
+      else if (song->voice[v].panned==PANNED_LEFT)
+	{
+	  while (c--)
+	    {
+	      left += li;
+	      if (left<0)
+		return;
+	      s=*sp++;
+	      MIXATION(left);
+	      lp++;
+	    }
+	}
+      else if (song->voice[v].panned==PANNED_RIGHT)
+	{
+	  while (c--)
+	    {
+	      left += li;
+	      if (left<0)
+		return;
+	      s=*sp++;
+	      lp++;
+	      MIXATION(left);
+	    }
+	}
+    }
+  else
+    {
+      /* Mono output.  */
+      while (c--)
+	{
+	  left += li;
+	  if (left<0)
+	    return;
+	  s=*sp++;
+	  MIXATION(left);
+	}
+    }
+}
+
+
+/**************** interface function ******************/
+
+void mix_voice(MidiSong *song, Sint32 *buf, int v, Sint32 c)
+{
+  Voice *vp = song->voice + v;
+  sample_t *sp;
+  if (vp->status==VOICE_DIE)
+    {
+      if (c>=MAX_DIE_TIME)
+	c=MAX_DIE_TIME;
+      sp=resample_voice(song, v, &c);
+      ramp_out(song, sp, buf, v, c);
+      vp->status=VOICE_FREE;
+    }
+  else
+    {
+      sp=resample_voice(song, v, &c);
+      if (song->encoding & PE_MONO)
+	{
+	  /* Mono output. */
+	  if (vp->envelope_increment || vp->tremolo_phase_increment)
+	    mix_mono_signal(song, sp, buf, v, c);
+	  else
+	    mix_mono(song, sp, buf, v, c);
+	}
+      else
+	{
+	  if (vp->panned == PANNED_MYSTERY)
+	    {
+	      if (vp->envelope_increment || vp->tremolo_phase_increment)
+		mix_mystery_signal(song, sp, buf, v, c);
+	      else
+		mix_mystery(song, sp, buf, v, c);
+	    }
+	  else if (vp->panned == PANNED_CENTER)
+	    {
+	      if (vp->envelope_increment || vp->tremolo_phase_increment)
+		mix_center_signal(song, sp, buf, v, c);
+	      else
+		mix_center(song, sp, buf, v, c);
+	    }
+	  else
+	    { 
+	      /* It's either full left or full right. In either case,
+		 every other sample is 0. Just get the offset right: */
+	      if (vp->panned == PANNED_RIGHT) buf++;
+	      
+	      if (vp->envelope_increment || vp->tremolo_phase_increment)
+		mix_single_signal(song, sp, buf, v, c);
+	      else 
+		mix_single(song, sp, buf, v, c);
+	    }
+	}
+    }
+}