[py] added constantq demo

diff --git a/python/demos/demo_constantq.py b/python/demos/demo_constantq.py
new file mode 100755 (executable)
index 0000000..cee1769
--- /dev/null
+++ b/python/demos/demo_constantq.py
@@ -0,0 +1,87 @@
+#! /usr/bin/env python
+
+import sys, os.path
+import numpy as np
+import aubio
+
+if __name__ == '__main__':
+
+    if len(sys.argv) < 2:
+        print ("usage: %s <inputfile>" % sys.argv[0])
+        sys.exit(1)
+    input_filename = sys.argv[1]
+
+    win_size = 8192 #2048 #1024
+    hop_size = win_size // 2
+    samplerate = 44100
+    bins_per_octave = 72 # 24 # 6, 12, 24, 36, 48, 72...
+
+    a_source = aubio.source(input_filename, samplerate, hop_size)
+    a_pvoc = aubio.pvoc(win_size, hop_size)
+    a_constantq = aubio.constantq(win_size, samplerate, bins_per_octave)
+
+    numbins = a_constantq.get_numbins()
+
+    print ('created constant-q with %d win_size, %d numbins, %d Hz' %
+            (win_size, numbins, samplerate))
+
+    read = hop_size
+
+    cqts = np.ndarray((0,numbins)).astype(aubio.float_type)
+
+    while read:
+        samples, read = a_source()
+        fftgrain = a_pvoc(samples)
+        cqt = a_constantq(fftgrain)
+        cqts = np.vstack([cqts, cqt])
+
+    print ('finished computing constant-q over %d frames of %d bins' % cqts.shape)
+    try:
+        import matplotlib.pyplot as plt
+        import matplotlib.ticker as ticker
+        plt.rc('font', size=8)
+        plt.rc('axes', titlesize=8)
+
+        fig, ax = plt.subplots(1)
+        ax.imshow(cqts.T, aspect='auto', origin='bottom', cmap=plt.cm.gray_r)
+        ax.axis([0, len(cqts), 0, len(cqts[0])])
+
+        time_step = hop_size / float(samplerate)
+        freq_start = 19.0 # TODO get actual low_freq
+        freq_step = 12./bins_per_octave
+        freq_end = freq_start + len(cqts[0]) * freq_step
+        #print ('plotting', end=" ")
+        #print ('x from 0 to %.2f (sec),' % (time_step * len(cqts)), end=" ")
+        #print ('y from %.2f to %.2f (midi note)' % (freq_start, freq_end))
+
+        ax.fmt_xdata = lambda x: "%.1f" % (x * time_step)
+        x_formatter = ticker.FuncFormatter(lambda x, pos: ax.fmt_xdata(x) )
+        ax.xaxis.set_major_formatter(x_formatter)
+        if 0:
+            total_duration = time_step * len(cqts)
+            if total_duration >= 60: rate = 10.
+            elif total_duration >= 10: rate = 5.
+            elif total_duration >= 3: rate = 1.
+            elif total_duration >= 1: rate = .2
+            elif total_duration < 1: rate = .1
+            #ax.xaxis.set_major_locator(ticker.FixedLocator(np.arange(0, len(cqts), rate/time_step)))
+            ax.xaxis.set_major_locator(ticker.MultipleLocator(base=rate/time_step))
+        else:
+            ax.xaxis.set_major_locator(ticker.AutoLocator())
+            #ax.xaxis.set_major_locator(ticker.MaxNLocator(nbins=10, symmetric=True))
+            #ax.xaxis.set_major_locator(ticker.MaxNLocator(integer=True, steps=[1]))
+            #ax.xaxis.set_major_locator(ticker.MultipleLocator(base=1./time_step))
+
+        ax.set_xlabel ('Time (s)')
+
+        ax.fmt_ydata = lambda y: "%.1f" % (y * freq_step + freq_start)
+        y_formatter = ticker.FuncFormatter(lambda y, pos: ax.fmt_ydata(y))
+        ax.yaxis.set_major_formatter(y_formatter)
+        ax.yaxis.set_major_locator(ticker.MultipleLocator(base=bins_per_octave))
+        ax.set_ylabel ('Frequency (midi)')
+
+        ax.set_title('Constant-Q tranform of %s' % os.path.basename(input_filename))
+
+        plt.show()
+    except ImportError:
+        print ('install matplotlib to plot results')