Added a simple gui and envelope to the signal

.gitignore

@@ -0,0 +1,2 @@
+*.pyc
+*.swp

littlemetronome/__main__.py

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+#!/usr/bin/env python
+from math import sin, pi
+import sys
+
+
+# INIT GTK and GST
+
+argv = sys.argv
+# work around gstreamer parsing sys.argv!
+sys.argv = []
+import gobject
+gobject.threads_init()
+
+import pygtk
+pygtk.require('2.0')
+
+import pygst
+pygst.require('0.10')
+
+import gst, gtk
+
+# always enable button images
+gtk.settings_get_default().set_long_property("gtk-button-images", True, "main")
+sys.argv = argv
+
+from . import mygtk
+mygtk.install()
+
+from array import array
+
+NAME = u"Little Metronome"
+
+sink_config = "autoaudiosink"
+rate = 48000.0
+freq = 400.0
+volume = 0.5
+t = 0
+
+if len(argv) > 1:
+    bpm = float(argv[1])
+else:
+    bpm = 60
+bps = bpm/60.0
+
+class Metronome(object):
+    def __init__(self, sink_config):
+        self.pipeline = gst.Pipeline()
+        self.t = 0
+        self.bpm = 80
+        self.volume = 0.5
+
+        source = gst.element_factory_make("appsrc")
+        source_caps = gst.Caps('audio/x-raw-float,rate=(int)%i,channels=(int)1,width=(int)32,endianness=(int)1234' % rate)
+        source.connect('need-data', self._need_data)
+        source.set_property('caps', source_caps)
+
+        convert = gst.element_factory_make("audioconvert")
+
+        sink = gst.parse_bin_from_description(sink_config, True)
+
+        self.pipeline.add_many(source, convert, sink)
+        gst.element_link_many(source, convert, sink)
+
+    def _need_data(self, src, length):
+        data = array('f')
+        bps = self._bps
+        volume = self.volume
+        for i in xrange(self.t, self.t+length):
+            tsec = i/rate
+            envelope = max(0.0, 1.0-((( ((tsec*bps)%1.0)/bps -0.05)*20.0)**4.0))
+            #on = 1/((tsec*bps)%1.0)
+            sample = sin(tsec*freq*pi*2.0)*envelope*volume
+            data.append(sample)
+        self.t += length
+        src.emit('push-buffer', gst.Buffer(data))
+
+
+    def get_bpm(self):
+        return self._bpm
+
+    def set_bpm(self, value):
+        self._bpm = value
+        self._bps = value/60.0
+
+    bpm = property(get_bpm, set_bpm)
+
+    def play(self):
+        self.t = 0
+        self.pipeline.set_state(gst.STATE_PLAYING)
+
+    def pause(self):
+        self.pipeline.set_state(gst.STATE_PAUSED)
+
+class BPMScale(mygtk.TextScale):
+    format = "%.1f BPM "
+    size = 10
+
+
+class MainWindow(gtk.Window):
+    def __init__(self, metronome):
+        gtk.Window.__init__(self,gtk.WINDOW_TOPLEVEL)
+
+        self.metronome = metronome
+
+        self.init_ui()
+
+    def init_ui(self):
+        self.set_title(NAME)
+
+        try:
+            self.set_icon(mygtk.iconfactory.get_icon("littlemetronome", 128))
+            pass
+        except gobject.GError:
+            print "could not load icon"
+
+        self.set_default_size(500, 200)
+        self.set_border_width(5)
+
+        self.accel_group = gtk.AccelGroup()
+        self.add_accel_group(self.accel_group)
+
+        vbox = gtk.VBox()
+        self.add(vbox)
+
+        tempo = BPMScale(gtk.Adjustment(80.00, 10.00, 400.0, 1.0, 0.5))
+        tempo.scale.connect("value-changed", self.tempo_changed)
+        self.tempo_changed(tempo)
+
+        form = mygtk.form([
+            ('Tempo', tempo),
+            ('Increase', None),
+            ('Meter', None),
+            ('Pattern', None)
+        ])
+
+        vbox.pack_start(form)
+
+        buttonbox = gtk.HButtonBox()
+        vbox.pack_end(buttonbox, False, False)
+
+        self.play_button = gtk.ToggleButton(gtk.STOCK_MEDIA_PLAY)
+        self.play_button.connect("toggled", self.play)
+        self.play_button.set_use_stock(True)
+        self.play_button.add_accelerator("clicked", self.accel_group, gtk.keysyms.Return, 0, ())
+        buttonbox.pack_start(self.play_button, False, False)
+
+        self.volume_button = gtk.VolumeButton()
+        self.volume_button.set_value(1.0)
+        self.volume_button.set_relief(gtk.RELIEF_NORMAL)
+        self.volume_button.connect("value-changed", self.volume_changed)
+        self.volume_changed(self.volume_button, None)
+        buttonbox.pack_start(self.volume_button, False, False)
+
+        self.connect("destroy", gtk.main_quit)
+
+    def volume_changed(self, sender, _):
+        self.metronome.volume = sender.get_value()
+
+    def tempo_changed(self, sender):
+        self.metronome.bpm = sender.get_value()
+
+    def play(self, sender):
+        if sender.get_active():
+            self.metronome.play()
+        else:
+            self.metronome.pause()
+
+
+if __name__ == "__main__":
+    metronome = Metronome(sink_config)
+
+    win = MainWindow(metronome)
+    win.show_all()
+
+    gtk.main()