Simple-effect.py

From PiTiViWiKi

#!/usr/bin/env python
"""Extends basic demo with a gnl composition"""

from demo import Demo, DemoException
import gtk
import gst
import sys
import os

def create_decodebin():
    try:
        return gst.element_factory_make("decodebin2")
    except:
        return gst.element_factory_make("decodebin")

class SimpleEffectDemo(Demo):
    __name__ = "Basic GStreamer Effect Demo"
    __usage__ = '''python %s file
    display file with a color_balance effect''' % sys.argv[0]
    __def_win_size__ = (320, 500)
    # <excerpt 1>
    def magic(self, pipeline, sink, args):

        def onPad(obj, pad, target):
            sinkpad = target.get_compatible_pad(pad, pad.get_caps())
            pad.link(sinkpad)
            return True

        assert os.path.exists(sys.argv[1])
        
        # create the following pipeline 
        # filesrc location = sys.argv[1] ! decodebin ! videobalance ! ...
        src = gst.element_factory_make("filesrc")
        src.set_property("location", sys.argv[1])
        decode = create_decodebin()
        
        self.balance = gst.element_factory_make("videobalance")
        
        pipeline.add(src, decode, self.balance)        
        src.link(decode)
        decode.connect("pad-added", onPad, self.balance)
        self.balance.link(sink)

        return
    # </excerpt>

    # <excerpt 2>
    # overriding from parent
    def customWidgets(self):
        """Create a control for each property in the videobalance
        widget"""
        
        # to be called a property value needs to change
        def onValueChanged(widget, prop):
            # set the corresponding property of the videobalance element
            self.balance.set_property(prop, widget.get_value())

        # videobalance has several properties, with the following range
        # and defaults
        properties = [("contrast", 0, 2, 1),
                      ("brightness", -1, 1, 0), 
                      ("hue", -1, 1, 0),
                      ("saturation", 0, 2, 1)]
    
        # create a place to hold our controls
        controls = gtk.VBox()
        labels = gtk.VBox()
        # for every propety, create a control and set its attributes
        for prop, lower, upper, default in properties:
            widget = gtk.HScale(); label = gtk.Label(prop)

            # set appropriate atributes
            widget.set_update_policy(gtk.UPDATE_CONTINUOUS)
            widget.set_value(default)
            widget.set_draw_value(True)
            widget.set_range(lower, upper)

            # connect to our signal handler, specifying the property
            # to adjust
            widget.connect("value-changed", onValueChanged, prop)
        
            # pack widget into box
            controls.pack_start(widget, True, True)
            labels.pack_start(label, True, False)

        layout = gtk.HBox()
        layout.pack_start(labels, False, False)
        layout.pack_end(controls, True, True)
        return layout

    # </excerpt>

if __name__ == '__main__':
    SimpleEffectDemo().run()