GTK drawing + Gstreamer

[Matteo Landi <matteo landi email it>]

Hi all,
i'm trying to develop a basic image processing that sources the
frames from the webcam.
Basically the gtk application is composed of three windows:
1 - drawing area displaying modified stream
2 - drawing area displaying the webcam stream (i used an xoverlay
 for the link between the gstreamer videosink and the drawing area)
3 - box containing settings for the webcam stream

I have a gst object that everytime it has a new frame, launch a callback
function. Inside this method i make the image process, and save the
result inside a gdk_pixbuff. Once the process is terminated, inside the
function, i call gdk_draw_pixbuf over the first drawing area. Is it correct to
draw over drawing areas from gstreamer callbacks? I suppose this is not
the right way of doing things, because my application crashes with x errors
such as BadLength, BadRequest ..
Have you got any ideas about it?
Thanks for the attention

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M@