karplus-strong in python

projekte/soundz/karplus-simple.py

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+############################################################
+#
+# karplus-simple.py
+#
+# Author: MV (http://electro-nut.blogspot.com/)
+#
+# Generates a plucked string sound WAV file using the
+# Karplus-Strong algorithm. (Simple version.)
+#
+############################################################
+from math import sin, pi
+from array import array
+from random import random
+
+import wave
+
+# KS params
+SR = 44100
+f = 220
+N = SR/f
+
+# WAV params
+NCHANNELS = 1
+SWIDTH = 2
+FRAME_RATE = 44100
+NFRAMES = 44100
+NSAMPLES = 44100
+# max - 128 for 8-bit, 32767 for 16-bit
+MAX_VAL= 32767
+
+# pluck
+buf = [random() - 0.5 for i in range(N)]
+
+#init samples 
+samples = []
+
+# KS - ring buffer
+bufSize = len(buf)
+for i in range(NSAMPLES):
+    samples.append(buf[0])
+    avg = 0.996*0.5*(buf[0] + buf[1])
+    buf.append(avg)
+    buf.pop(0)
+
+# samples to 16-bit to string
+tmpBuf = [int(x*MAX_VAL) for x in samples] 
+data = array('h', tmpBuf).tostring()
+
+# write out WAV file
+file = wave.open('karplus-simple.wav', 'wb')
+file.setparams((NCHANNELS, SWIDTH, FRAME_RATE, NFRAMES,
+                'NONE', 'noncompressed'))
+file.writeframes(data)
+file.close()

projekte/soundz/karplus.py

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+############################################################
+#
+# karplus.py
+#
+# Author: MV (http://electro-nut.blogspot.com/)
+#
+# Generates a plucked string sound WAV file using the
+# Karplus-Strong algorithm. 
+#
+############################################################
+from math import sin, pi
+from array import array
+from random import random
+import wave
+
+# KS params
+SR = 44100
+f = 220
+
+# WAV params
+NCHANNELS = 1
+SWIDTH = 2
+FRAME_RATE = 44100
+NFRAMES = 44100
+NSAMPLES = 44100*2
+# max - 128 for 8-bit, 32767 for 16-bit
+MAX_VAL= 32767
+
+class String:
+    def __init__(self, freq, SR):
+        self.freq = freq
+        self.N = SR/freq
+    # 'pluck' string
+    def pluck(self):
+        self.buf = [random() - 0.5 for i in range(self.N)]
+    # return current sample, increment step
+    def sample(self):
+        val = self.buf[0]
+        avg = 0.996*0.5*(self.buf[0] + self.buf[1])
+        self.buf.append(avg)
+        self.buf.pop(0)
+        return val
+    
+str1, str2 = String(196, SR), String(440, SR)
+
+str1.pluck()
+str2.pluck()
+
+samples = []
+
+for i in range(NSAMPLES):
+    sample = str1.sample()
+    if(i > NSAMPLES/8):
+        sample += str2.sample()
+    samples.append(sample)
+
+# samples to 16-bit to string
+tmpBuf = [int(x*MAX_VAL) for x in samples] 
+data = array('h', tmpBuf).tostring()
+
+# write out WAV file
+file = wave.open('karplus.wav', 'wb')
+file.setparams((NCHANNELS, SWIDTH, FRAME_RATE, NFRAMES,
+                'NONE', 'noncompressed'))
+file.writeframes(data)
+file.close()