[gst-devel] Caps and properties

[Wim Taymans]

On 03 Jan 2001 14:03:10 +0000, Richard Boulton wrote:
> I've just been wondering: is there any way to specify a "preferred" value
> foe a property?  For example, if I have:
> 
> static GstPadFactory sink_factory = {
>   "sink",
>   GST_PAD_FACTORY_SINK,
>   GST_PAD_FACTORY_ALWAYS,
>   GST_PAD_FACTORY_CAPS(
>      "esdsink_sink",
>      "audio/raw",
>      "format",   GST_PROPS_INT (1),
>      "depth",    GST_PROPS_LIST (GST_PROPS_INT (8), GST_PROPS_INT (16)),
>      "rate",     GST_PROPS_INT_RANGE (8000, 48000),
>      "channels", GST_PROPS_LIST (GST_PROPS_INT (1), GST_PROPS_INT (2)),
>      "", GST_PROPS_BOOLEAN (TRUE)
>   ),
>   NULL
> };
> 
> this specifies that I am happy with any value of rate in the range 8000 to
> 48000.  (Actually I believe that esd will do its best to cope with things
> well outside this range, but thats beside the point).
> Is there any way to specify a "preferred" value of a property.  For
> example, an entire pipeline might be happy with 8000 <= rate <= 48000: who
> decides what actual value to use?
> 

This will be implemented in the caps negociation procedure. This will
basically be a procedure
a plugin has to implement to decide on the best possible way to talk to
another pad. This will
allow a much more flexible way of dealing with caps than the 'prefered'
property value, methinks.

We have no clear indication on how to implement caps negociation yet... 

> Also, while I'm asking questions:  Is "GST_IS_BUFFER" something which has
> been deprecated, or just not yet implemented?  It's in quite a few of the
> plugins, commented out, and in the example plugin too (not commented out).
> 

It is deprecated, GstBuffer is not a Gtk+ object, hence you cannot use
the normal GST_IS_*
mechanisms for type checking. This is for performance reasons.

wim

> -- 
> Richard
> 
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