import gobject
gobject.threads_init ()
import gst

class Switch (object):
    def __init__ (self):
        self.loop = gobject.MainLoop ()
        self.pipeline = gst.Pipeline ()
        self.bus = self.pipeline.get_bus ()
        
        self.bus.connect ("message::eos", self._bus_message_eos_cb)
        self.bus.connect ("message::error", self._bus_message_error_cb)

        self.video1 = gst.element_factory_make ("videotestsrc")
        self.video2 = gst.element_factory_make ("videotestsrc")
        self.video2.props.pattern = 4

        self.csp = gst.element_factory_make ("ffmpegcolorspace")
        self.sink = gst.element_factory_make ("ximagesink")

        self.pipeline.add (self.video1, self.csp, self.sink)

        gst.element_link_many (self.video1, self.csp, self.sink)

    def _bus_message_eos_cb (self, bus, message):
        print "eos"
        self.loop.quit ()

    def _bus_message_error_cb (self, bus, message):
        print "error", message
        self.loop.quit ()

    def _pad_blocked_cb (self, pad, blocked):
        pad.unlink (pad.get_peer ())
        self.pipeline.add (self.video2)
        self.video2.link (self.csp)
        self.video2.set_state (gst.STATE_PLAYING)

    def _timeout_cb (self):
        self.video1.get_pad ("src").set_blocked_async (True,
            self._pad_blocked_cb)

    def start (self):
        self.pipeline.set_state (gst.STATE_PLAYING)
        gobject.timeout_add (10000, self._timeout_cb)
        self.loop.run ()

if __name__ == '__main__':
    Switch ().start ()