getting GdkPixbuf from gdkpixbufsink

[TimSC]

Hello all,

I am looking for some help getting the object GdkPixbuf from  
gdkpixbufsink. I am working in image processing so I want to get the  
image buffer for each frame. My priorities are to have a reliable and  
conceptually simple way of getting the buffer.

I have started by modifying gst-player-0.0.0, changed it to use the  
gdkpixbufsink sink and waiting to process messages on the bus. I am  
seeing the element/pixbuf messages without a problem. I then call the  
following on the bus message:

buff = gst_structure_get_value (msg->structure,"pixbuf");

which gives me a non-zero pointer. I was expecting that is a GdkPixbuf  
object. The problem I get is when I do GDK_IS_PIXBUF(buff) it returns  
false. Any ideas why?

Or am I meant to retrieve "last-pixbuf" from the sink directly?

If more detail is needed, the code is here:  
http://www.sheerman-chase.org.uk/temp/gst-player-pixel.tar.gz

Tim



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[Tim-Philipp Müller-2]

On Fri, 2009-01-09 at 17:17 +0000, [hidden email] wrote:

Hi,

> I have started by modifying gst-player-0.0.0, changed it to use the  
> gdkpixbufsink sink and waiting to process messages on the bus. I am  
> seeing the element/pixbuf messages without a problem. I then call the  
> following on the bus message:
>
> buff = gst_structure_get_value (msg->structure,"pixbuf");
>
> which gives me a non-zero pointer. I was expecting that is a GdkPixbuf  
> object. The problem I get is when I do GDK_IS_PIXBUF(buff) it returns  
> false. Any ideas why?

It returns a const GValue * from which you can retrieve the GdkPixbuf
object via

  pixbuf = g_value_dup_object (val);

(which gives you a reference to the pixbuf which you need to drop with
g_object_unref(pixbuf) when you don't need it any longer)


> Or am I meant to retrieve "last-pixbuf" from the sink directly?

You can do that as well. The "last-pixbuf" property is useful if you
want to check the pixbuf in your own time/interval and you're just
interested in the current pixbuf and not interested whether you're
missing any or not.

If you want to evaluate each and every pixbuf, you need to process the
messages.

There's also an example at:
http://webcvs.freedesktop.org/gstreamer/gst-plugins-good/tests/icles/gdkpixbufsink-test.c?view=markup

Cheers
 -Tim



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