Bizarre Intermittent Error on Video (GStreamer)

Question

I have a project that runs Python 2.7, PyGTK 2.24, and the most recent version of PyGST.

I am getting a weird intermittent error in the following code. With the first, longer error, the video will play just fine, and the error will only appear AFTER I close the video window. The second prevents the window from opening at all.

import pygtk
pygtk.require('2.0')
import gtk, pango
import pygst
pygst.require('0.10')
import gst
import Trailcrest
import os, sys

class Video:

    def __init__(self):

        def on_message(bus, message): 
            if message.type == gst.MESSAGE_EOS: 
                # End of Stream 
                player.set_state(gst.STATE_NULL) 
            elif message.type == gst.MESSAGE_ERROR: 
                player.set_state(gst.STATE_NULL) 
                (err, debug) = message.parse_error() 
                print "Error: %s" % err, debug

        def on_sync_message(bus, message):
            if message.structure is None: 
                return False 
            if message.structure.get_name() == "prepare-xwindow-id":
                if sys.platform == "win32":
                    win_id = videowidget.window.handle
                else:
                    win_id = videowidget.window.xid
                assert win_id
                imagesink = message.src 
                imagesink.set_property("force-aspect-ratio", True)
                imagesink.set_xwindow_id(win_id) 

        win = gtk.Window()
        win.set_resizable(False)
        win.set_has_frame(False)
        win.set_position(gtk.WIN_POS_CENTER)

        fixed = gtk.Fixed()
        win.add(fixed)
        fixed.show()

        videowidget = gtk.DrawingArea()
        fixed.put(videowidget, 0, 0)
        videowidget.set_size_request(640, 480)
        videowidget.show()

        # Setup GStreamer 
        player = gst.element_factory_make("playbin", "MultimediaPlayer")
        bus = player.get_bus() 
        bus.add_signal_watch() 
        bus.enable_sync_message_emission() 
        #used to get messages that GStreamer emits 
        bus.connect("message", on_message) 
        #used for connecting video to your application 
        bus.connect("sync-message::element", on_sync_message)
        player.set_property("uri", "file://" + os.getcwd() + "/VID/SEQ-GAME-OPEN.ogv") 
        player.set_state(gst.STATE_PLAYING)

        win.show()

def main():
    gtk.gdk.threads_init()
    gtk.main()
    return 0

if __name__ == "__main__":
    Video()
    main()

The program 'Video.py' received an X Window System error. This probably reflects a bug in the program. The error was 'BadIDChoice (invalid resource ID chosen for this connection)'. (Details: serial 373 error_code 14 request_code 1 minor_code 0) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.)

A quick note on this...I followed the instructions and ran "python Video.py --sync" in command line (I'm on Kubuntu), and I got that message AGAIN.

Here's the other error - the one that prevents playback at all.

python: ../../src/xcb_io.c:221: poll_for_event: Assertion `(((long) (event_sequence) - (long) (dpy->request)) <= 0)' failed. Aborted

These will literally alternate, though not perfectly. I could get three of the first, two of the second, one first, one second, two first, etc. It is always different.

What the devil is going on here?

Answer 1

You need to synchronise with X server to get window xid.

Here is how:

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