Diff: bitcrush.c

Revision:

0:cb80470434eb

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bitcrush.c	Tue Oct 28 12:19:42 2014 +0000
@@ -0,0 +1,136 @@
+/*
+Copyright 2013 Paul Soulsby www.soulsbysynths.com
+    This file is part of Atmegatron.
+
+    Atmegatron is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Atmegatron 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 a copy of the GNU General Public License
+    along with Atmegatron.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+//*******THIS IS THE WAVE CRUSHER***************
+
+#include "atmegatron.h"
+
+//local vars
+byte sampshft = 8;
+byte samphold = 32;
+
+//local lets and gets
+byte bitcrush_type = 0;   //0=off
+boolean bitcrush_prefilt = false;  
+
+//lets and gets
+//set the bitcrush parameters
+void BitCrush_Let_Type(byte newtype)
+{
+  if (newtype!=bitcrush_type){
+    bitcrush_type = newtype;
+    switch (bitcrush_type){
+      case 0:              //Bit crush off
+        break;
+      case 1:                        
+        sampshft = 5;      //sampshft decreases bit depth
+        samphold = 1;      //sampshft decrease sample frequency
+        break;
+      case 2:    
+        sampshft = 6;
+        samphold = 1;
+        break;
+      case 3:    
+        sampshft = 7;
+        samphold = 1;
+        break;        
+      case 4:    
+        sampshft = 4;
+        samphold = 2;
+        break;
+      case 5:    
+        sampshft = 5;
+        samphold = 2;
+        break;
+      case 6:    
+        sampshft = 6;
+        samphold = 2;
+        break;
+      case 7:    
+        sampshft = 7;
+        samphold = 2;
+        break;
+      case 8:    
+        sampshft = 4;
+        samphold = 4;
+        break;
+      case 9:    
+        sampshft = 5;
+        samphold = 4;
+        break;        
+      case 10:    
+        sampshft = 6;
+        samphold = 4;
+        break;        
+      case 11:    
+        sampshft = 7;
+        samphold = 4;
+        break;       
+      case 12:    
+        sampshft = 4;
+        samphold = 8;
+        break;
+      case 13:    
+        sampshft = 5;
+        samphold = 8;
+        break;
+      case 14:    
+        sampshft = 6;
+        samphold = 8;
+        break;
+      case 15:    
+        sampshft = 7;
+        samphold = 8;
+        break; 
+    }
+  }
+}
+
+
+byte BitCrush_Get_Type(void)
+{
+  return bitcrush_type;
+}
+
+
+//set pre-filter mode.  this processes the bitcrush before the filter (rather than before distortion)
+void BitCrush_Let_PreFilt(boolean newprefilt)
+{
+  bitcrush_prefilt = newprefilt;
+}
+
+
+boolean BitCrush_Get_PreFilt(void)
+{
+  return bitcrush_prefilt;
+}
+
+//process the wavetable
+void BitCrush_Process(void)
+{
+  byte i;
+  sample_t samp = 0;
+  for (i=0;i<WAVE_LEN;i++){        //cycle through wavetable
+    if (i % samphold == 0){        //every samphold samples
+      samp = Wave_Get_Process(i);  //get the wavetable sample
+      samp = samp >> sampshft;     //shift sampshft bits, to reduce bit rate
+      samp = samp << sampshft;     //shift back again to restore amplitude
+    }
+    Wave_Let_Process(i, samp);     //write back to wavetable 
+  }
+}