Is it possible to be notified about plugins readonly parameter changes?

[wellington wallace]

When I have the time I will try to take a look at the lv2/ladspa plugin
source :D But as I have never done a Gstreamer or lv2/ladspa plugin before
I am not sure I will succeed and be able to provide patches.

Best regards,

             Wellington

On Wed, Mar 21, 2018 at 6:23 PM, Thibault Saunier <tsaunier at gnome.org>
wrote:

> > Maybe there is a limitation in the LADSPA or LV2 support and there is no
> internal calling for the notify property when GStreamer updates the the
> readonly properties of these kind of plugins. Or maybe something is missing
> in the Python bindings.
>
> From what you describe I would guess something is missing in the
> lv2/ladspa GStreamer plugin, patches welcome :-)
>
> Regards,
>
> Thibault Saunier
>
> On Wed, Mar 21, 2018 at 1:00 AM, wellington wallace
> <wellingtonwallace at gmail.com> wrote:
> > Hi Michael
> >
> > I tried what you suggested and the callback is called only when I invoke
> > GObject notify method. Nothing happens when the plugin updates the
> property.
> > I will detail a little more my situation. I am the developer of this
> > application https://github.com/wwmm/pulseeffects. In it I use a few
> LADSPA
> > and LV2 plugins that write on readonly parameters information like the
> > current audio delay, attenuation or latency. I would like to show this
> kind
> > of information without using a combination of GLib.timeout_add_seconds
> and
> > get_property like I am doing know. Things like the delay of the delay
> plugin
> > do not change all the time like the attenuation of a compressor. So it
> does
> > not make sense to get this value in a timer.
> >
> > Maybe there is a limitation in the LADSPA or LV2 support and there is no
> > internal calling for the notify property when GStreamer updates the the
> > readonly properties of these kind of plugins. Or maybe something is
> missing
> > in the Python bindings.
> >
> > Best regards,
> >
> >                    Wellington
> >
> >
> > On Tue, Mar 20, 2018 at 1:05 PM, Michael Gruner
> > <michael.gruner at ridgerun.com> wrote:
> >>
> >> Hi Wellington
> >>
> >> Every GObject (GstElements included) may emit a signal every time one of
> >> its properties change. This signal is named “notify::<property name>”.
> So,
> >> for example, if you’d like to register a callback every time the “sync”
> >> property changes, you would do something like:
> >>
> >> /* Activate property change notification */
> >> g_object_notify (G_OBJECT (sink), “sync”);
> >>
> >> /* Register a callback */
> >> g_signal_connect (sink, "notify::sync",
> >>       G_CALLBACK (sync_update_callback), NULL);
> >>
> >> You may find more info in the notify signal documentation:
> >>
> >> https://developer.gnome.org/gobject/stable/gobject-The-
> Base-Object-Type.html#GObject-notify
> >>
> >>
> >> —
> >> Michael Gruner <michael.gruner at ridgerun.com>
> >> Embedded Linux and GStreamer solutions
> >> RidgeRun Engineering
> >> Contact Us - http://www.ridgerun.com/#!contact/c3vn
> >>
> >> On Mar 20, 2018, at 09:18, wellington wallace
> >> <wellingtonwallace at gmail.com> wrote:
> >>
> >> Hi!
> >>
> >> I would like to be notified when an readonly parameter changes. Consider
> >> for example the current delay or latency of ladspa or lv2 delay plugin.
> I
> >> tried the following with no success:
> >>
> >> self.delay.bind_property('left-delay', self.ui_value, 'value',
> >> GObject.BindingFlags.DEFAULT)
> >>
> >> When the property is writable I am notified about its changes but not
> when
> >> it is readonly. I know that the plugin code made changes to the
> parameter
> >> because I can see them doing print(self.delay.get_property(
> 'left-delay)).
> >>
> >> Is there a way to be notified about these changes without having to
> >> periodically calling get_property?
> >>
> >> Best regards,
> >>
> >>                  Wellington
> >>
> >> --
> >> Prof.° Wellington Wallace Miguel Melo
> >>
> >> CEFET/RJ Uned Nova Iguaçu
> >>
> >> _______________________________________________
> >> gstreamer-devel mailing list
> >> gstreamer-devel at lists.freedesktop.org
> >> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
> >>
> >>
> >
> >
> >
> > --
> > Prof.° Wellington Wallace Miguel Melo
> >
> > CEFET/RJ Uned Nova Iguaçu
> >
> >
> > _______________________________________________
> > gstreamer-devel mailing list
> > gstreamer-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
> >
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>



-- 
Prof.° Wellington Wallace Miguel Melo

CEFET/RJ Uned Nova Iguaçu
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