[gst-devel] RFC: argument system?

Thomas Nyberg thomas at codefactory.se
Sun May 13 15:55:19 CEST 2001

On Sun, May 13, 2001 at 12:30:20AM -0700, Erik Walthinsen wrote:

> It makes me think that we may indeed want to build our own control system
> for elements, but I'm hesitant to do that for quite a number of reasons.
> First of all, the gtk/glib functions already exist, have a number of
> features that are useful for more unusual plugins (see
> http://gstreamer.net/lame-args.png for an example), and is still evolving
> in glib 2.0.
> Then again, we may want to consider that there are different classes of
> controls for different classes of elements.  It could be that we use the
> existing gtk/glib system for common arguments like those found in lame,
> but our own system for things like mix levels, etc.  Basically anything
> that could be changed frequently, even the existance of a given argument
> is dynamic itself.
> steveb's dynparms proposal may be the right way to go about this,
> especially if it can be done efficiently and without significant code in
> the common case (that is, less frequent changes that are still
> time-critical).  If it's designed to be efficient at *both* dynamic
> dimensions somehow, it would be ideal.

I agree on this, if you look at ladspa, you see a nice system for
an application to determine which parameters that exists, and use them.
The "ladspa-way" also offers hints, descriptions and other things for
an application to retrieve. This is something that I believe is vital
to add to GStreamer. The dynparams-proposal solves this problem in a
way. The important thing is to have an easy API which is flexible

If we are going to provide support for LADSPA, it is important that
we have an API which we can use to set these parameters too. Dynparams
should be able to solve this problem though, and that is why we should
concentrate on this feature.

An application should be able to probe the parameters of an element,
determine what each of them does, what range of values that are
acceptable, and so on... It makes the elements more powerful than
before, since more dynamic things can be added, more options and so
on... <pun>I really can't see how GStreamer could do without it</pun>


/Thomas <thomas at codefactory.se>

Thomas Nyberg                    thomas.nyberg at codefactory.se
CodeFactory AB                   http://www.codefactory.se/
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