changeset 2:7b9a06f64ab1

synthesis and delay added

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dsp-delay.py	Wed Sep 12 20:44:28 2012 +0100
@@ -0,0 +1,79 @@
+import numpy as np
+from scikits.audiolab import Sndfile
+from scikits.audiolab import Format
+
+#################################################
+######## CREATING A SOUND FILE INSTANCE #########
+#################################################
+
+# create Sndfile instance with our example audio file
+f = Sndfile('viola.wav', 'r')
+
+
+#################################################
+######## EXTRACTING AUDIO FILE META-DATA ########
+#################################################
+
+# extract and print sample rate
+fs = f.samplerate
+print "sample rate: ",fs
+
+# extract and print the number of channels
+nc = f.channels
+print "number of channels: ",nc
+
+# extract the number of samples
+nsamples = f.nframes
+
+
+#################################################
+######## READ AUDIO SAMPLES FROM THE FILE #######
+#################################################
+
+# we can read audio samples using the read_frame method
+data = f.read_frames(nsamples)
+
+
+#################################################
+########## APPLY A DELAY TO THE SAMPLES #########
+#################################################
+
+# delay in samples
+delay = fs/2
+
+# volume of delayed sound
+alpha = 0.75
+
+# create an empty array for the output
+out = np.zeros(data.size)
+
+# for every sample in the array
+for i in range(data.size):
+
+    # if we are safe to apply the delay without negative indexing
+    if (i >= delay):
+        out[i] = data[i] + data[i-delay]*alpha
+    else:
+        out[i] = data[i] # hacky
+
+
+#################################################
+########## WRITING TO A NEW AUDIO FILE ##########
+#################################################
+
+# create a name for the new file
+new_filename = 'delayed_audio.wav'
+
+# Create a Sndfile instance for writing wav files @ 44100 Hz
+format = Format('wav')
+f = Sndfile(new_filename, 'w', format, 1, 44100)
+
+# Write out the samples to an audio file
+f.write_frames(out)
+
+# close the audio file
+f.close()
+
+#################################################
+#################################################
+#################################################

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/synthesize-mono-noise-with-numpy.py	Wed Sep 12 20:44:28 2012 +0100
@@ -0,0 +1,38 @@
+import numpy as np
+from scikits.audiolab import Sndfile
+from scikits.audiolab import Format
+
+
+#################################################
+############ CREATE SOME RANDOM NOISE ###########
+#################################################
+
+# set our sampling frequency
+fs = 44100
+
+# create a numpy array that can hold 3 seconds of sound
+noise = np.empty(3*fs)
+
+# set each element to a random value (noise)
+for i in range(noise.size):
+    # generate random value and turn it down!
+    noise[i] = np.random.random()*0.2
+
+
+#################################################
+########## WRITING NOISE TO AUDIO FILE ##########
+#################################################
+
+# create a name for the new file
+new_filename = 'noise.wav'
+
+# Create a Sndfile instance for writing wav files @ 44100 Hz
+format = Format('wav')
+f = Sndfile(new_filename, 'w', format, 1, fs)
+
+# Write out the samples to the file
+f.write_frames(noise)
+
+# close the audio file
+f.close()
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/synthesize-stereo-sines-with-numpy.py	Wed Sep 12 20:44:28 2012 +0100
@@ -0,0 +1,49 @@
+import numpy as np
+from scikits.audiolab import Sndfile
+from scikits.audiolab import Format
+
+
+#################################################
+############## CREATE A SINE TONE ###############
+#################################################
+
+# set our sampling frequency
+fs = 44100
+
+# create a numpy array that can hold 3 seconds of sound
+tone = np.zeros((3*fs,2))
+
+# set frequency to 440Hz
+freq = 440
+
+# set volume to 0.3
+amp = 0.3
+
+# set values of each channel
+for i in range(tone.shape[0]):
+    
+    # calculate phase value
+    phaseVal = np.float(i)/np.float(fs)
+    
+    # generate tone and set volume for left and right
+    tone[i][0] = np.sin(2*np.pi*freq*phaseVal)*amp
+    tone[i][1] = np.sin(2*np.pi*freq*phaseVal)*amp
+
+
+#################################################
+########## WRITING TONES TO AUDIO FILE ##########
+#################################################
+
+# create a name for the new file
+new_filename = 'tone.wav'
+
+# Create a Sndfile instance for writing wav files @ 44100 Hz
+format = Format('wav')
+f = Sndfile(new_filename, 'w', format, 2, fs)
+
+# Write out the samples to the file
+f.write_frames(tone)
+
+# close the audio file
+f.close()
+