python/demos/demo_mel-energy.py: added simple mel energy bands demo

diff --git a/python/demos/demo_mel-energy.py b/python/demos/demo_mel-energy.py
new file mode 100755 (executable)
index 0000000..5a1da07
--- /dev/null
+++ b/python/demos/demo_mel-energy.py
@@ -0,0 +1,70 @@
+#! /usr/bin/env python
+
+import sys
+from aubio import fvec, source, pvoc, filterbank
+from numpy import vstack, zeros
+from demo_waveform_plot import set_xlabels_sample2time
+
+win_s = 512                 # fft size
+hop_s = win_s / 4           # hop size
+
+if len(sys.argv) < 2:
+    print "Usage: %s <filename> [samplerate]" % sys.argv[0]
+    sys.exit(1)
+
+filename = sys.argv[1]
+
+samplerate = 0
+if len( sys.argv ) > 2: samplerate = int(sys.argv[2])
+
+s = source(filename, samplerate, hop_s)
+samplerate = s.samplerate
+
+pv = pvoc(win_s, hop_s)
+
+f = filterbank(40, win_s)
+f.set_mel_coeffs_slaney(samplerate)
+
+energies = zeros((40,))
+o = {}
+
+total_frames = 0
+downsample = 2
+
+while True:
+    samples, read = s()
+    fftgrain = pv(samples)
+    new_energies = f(fftgrain)
+    print '%f' % (total_frames / float(samplerate) ),
+    print ' '.join(['%f' % b for b in new_energies])
+    energies = vstack( [energies, new_energies] )
+    total_frames += read
+    if read < hop_s: break
+
+if 1:
+    print "done computing, now plotting"
+    import matplotlib.pyplot as plt
+    from demo_waveform_plot import get_waveform_plot
+    fig = plt.figure()
+    plt.rc('lines',linewidth='.8')
+    wave = plt.axes([0.1, 0.75, 0.8, 0.19])
+    get_waveform_plot(filename, samplerate, block_size = hop_s, ax = wave )
+    wave.yaxis.set_visible(False)
+    wave.xaxis.set_visible(False)
+
+    n_plots = len(energies.T)
+    all_desc_times = [ x * hop_s  for x in range(len(energies)) ]
+    for i, band in enumerate(energies.T):
+        ax = plt.axes ( [0.1, 0.75 - ((i+1) * 0.65 / n_plots),  0.8, 0.65 / n_plots], sharex = wave )
+        ax.plot(all_desc_times, band, '-', label = 'band %d' % i)
+        #ax.set_ylabel(method, rotation = 0)
+        ax.xaxis.set_visible(False)
+        ax.yaxis.set_visible(False)
+        ax.axis(xmax = all_desc_times[-1], xmin = all_desc_times[0])
+        ax.annotate('band %d' % i, xy=(-10, 10),  xycoords='axes points',
+                horizontalalignment='right', verticalalignment='bottom',
+                )
+    set_xlabels_sample2time( ax, all_desc_times[-1], samplerate) 
+    #plt.ylabel('spectral descriptor value')
+    ax.xaxis.set_visible(True)
+    plt.show()