Re: Gst::Caps and the "caps" property.

[José Alburquerque <jaalburquerque cox net>]

Victor Bogado da Silva Lins wrote:
> On Sun, 2008-09-14 at 14:26 -0400, José Alburquerque wrote:
>   
> > Gst::Element does not directly have a caps property.  Instead, use the 
> > pads of the element to set the caps property that way.
> >
> >     
>
> I create the pipeline in the command line as that 
>
> $ gst-launch -p multifilesrc location=../testes/chess/IMG_%04d.JPG
> index=3425 num-buffers=36 caps=image/jpeg,framerate=15/1 ! jpegdec !
> xvimagesink
>
> and it work correctly, 

The command line (using gst-launch) operates somewhat differently from 
what needs to be done in a program.  I believe gst-inspect allows for 
caps to be passed that way and handles it differently than what one 
would have to do in a program.

> but if I set the 'src' pad to have the caps in my
> test program it don't respect the framerate I stated in the caps. 

I understand.

> Also
> the warning gst outputs seems to indicate that there is a property
> called caps but I am trying to set it with an incompatible pointer. 
>
> If I try to setup a nonexistent property I get the following runtime
> warning : 
>
> (teste:30218): GLib-GObject-WARNING **: IA__g_object_set_property:
> object class `GstMultiFileSrc' has no property named `blah'
>   

Even so, it would be best to use the interface already specified.  If 
you use gst-inspect on the element (e.g. `gst-inspect multifilesrc') 
you'll see a list of the properties it supports (see also the GStreamer 
docs on using elements as GObjects: 
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/section-elements-properties.html).  
There should be a way to set the caps on the pad because it would seem 
to be the correct way to get this done (see the "Pads and Capabilities" 
section: 
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/chapter-pads.html).

--
José Alburquerque