Question

I’m trying to work with GStreamer. I’m following a tutorial (http://pygstdocs.berlios.de/pygst-tutorial/pipeline.html) that gives me the following code:

#!/usr/bin/env python

import sys, os
import pygtk, gtk, gobject
import pygst
pygst.require("0.10")
import gst

class GTK_Main:

    def __init__(self):
        window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        window.set_title("Mpeg2-Player")
        window.set_default_size(500, 400)
        window.connect("destroy", gtk.main_quit, "WM destroy")
        vbox = gtk.VBox()
        window.add(vbox)
        hbox = gtk.HBox()
        vbox.pack_start(hbox, False)
        self.entry = gtk.Entry()
        hbox.add(self.entry)
        self.button = gtk.Button("Start")
        hbox.pack_start(self.button, False)
        self.button.connect("clicked", self.start_stop)
        self.movie_window = gtk.DrawingArea()
        vbox.add(self.movie_window)
        window.show_all()

        self.player = gst.Pipeline("player")
        source = gst.element_factory_make("filesrc", "file-source")
        demuxer = gst.element_factory_make("oggdemux", "demuxer")
        demuxer.connect("pad-added", self.demuxer_callback)
        self.video_decoder = gst.element_factory_make("theoradec", "video-decoder")
        self.audio_decoder = gst.element_factory_make("mad", "audio-decoder")
        audioconv = gst.element_factory_make("audioconvert", "converter")
        audiosink = gst.element_factory_make("autoaudiosink", "audio-output")
        videosink = gst.element_factory_make("autovideosink", "video-output")
        self.queuea = gst.element_factory_make("queue", "queuea")
        self.queuev = gst.element_factory_make("queue", "queuev")
        colorspace = gst.element_factory_make("ffmpegcolorspace", "colorspace")

        self.player.add(source, demuxer, self.video_decoder, self.audio_decoder, audioconv,
            audiosink, videosink, self.queuea, self.queuev, colorspace)
        gst.element_link_many(source, demuxer)
        gst.element_link_many(self.queuev, self.video_decoder, colorspace, videosink)
        gst.element_link_many(self.queuea, self.audio_decoder, audioconv, audiosink)

        bus = self.player.get_bus()
        bus.add_signal_watch()
        bus.enable_sync_message_emission()
        bus.connect("message", self.on_message)
        bus.connect("sync-message::element", self.on_sync_message)

    def start_stop(self, w):
        if self.button.get_label() == "Start":
            filepath = self.entry.get_text()
            if os.path.isfile(filepath):
                self.button.set_label("Stop")
                self.player.get_by_name("file-source").set_property("location", filepath)
                self.player.set_state(gst.STATE_PLAYING)
        else:
            self.player.set_state(gst.STATE_NULL)
            self.button.set_label("Start")

    def on_message(self, bus, message):
        t = message.type
        if t == gst.MESSAGE_EOS:
            self.player.set_state(gst.STATE_NULL)
            self.button.set_label("Start")
        elif t == gst.MESSAGE_ERROR:
            err, debug = message.parse_error()
            print "Error: %s" % err, debug
            self.player.set_state(gst.STATE_NULL)
            self.button.set_label("Start")

    def on_sync_message(self, bus, message):
        if message.structure is None:
            return
        message_name = message.structure.get_name()
        if message_name == "prepare-xwindow-id":
            imagesink = message.src
            imagesink.set_property("force-aspect-ratio", True)
            gtk.gdk.threads_enter()
            imagesink.set_xwindow_id(self.movie_window.window.xid)
            gtk.gdk.threads_leave()

    def demuxer_callback(self, demuxer, pad):
        if pad.get_property("template").name_template == "video_%02d":
            qv_pad = self.queuev.get_pad("sink")
            pad.link(qv_pad)
        elif pad.get_property("template").name_template == "audio_%02d":
            qa_pad = self.queuea.get_pad("sink")
            pad.link(qa_pad)

GTK_Main()
gtk.gdk.threads_init()
gtk.main()

I’m getting the following error when I try and play a .ogv file.

videotest.py:88: Warning: g_object_set_qdata: assertion `G_IS_OBJECT
(object)’ failed if pad.get_property(“template”).name_template ==
“video_%02d”: Traceback (most recent call last): File
“videotest.py”, line 88, in demuxer_callback
if pad.get_property(“template”).name_template == “video_%02d”:
AttributeError: ‘NoneType’ object has no attribute ‘name_template’
Traceback (most recent call last): File “videotest.py”, line 88, in
demuxer_callback
if pad.get_property(“template”).name_template == “video_%02d”:
AttributeError: ‘NoneType’ object has no attribute ‘name_template’

I really need to be able to play video. How do I fix this?

Answer 1

It is not reliable to determine pad type by it’s template name because it does not always have this property.

It’s better to check capabilities. Here is diff:

@@ -85,10 +85,11 @@
             gtk.gdk.threads_leave()

     def demuxer_callback(self, demuxer, pad):
-        if pad.get_property("template").name_template == "video_%02d":
+        typ = pad.get_caps()[0].get_name()
+        if typ.startswith("video"):
             qv_pad = self.queuev.get_pad("sink")
             pad.link(qv_pad)
-        elif pad.get_property("template").name_template == "audio_%02d":
+        elif typ.startswith("audio"):
             qa_pad = self.queuea.get_pad("sink")
             pad.link(qa_pad)