[LV2] Ui update rate

[Robin Gareus]

On 05/04/2013 07:38 PM, hermann meyer wrote:
> Am 30.04.2013 16:10, schrieb Harry van Haaren:
>> On Tue, Apr 30, 2013 at 3:00 PM, hermann meyer <brummer- at web.de
>> <mailto:brummer- at web.de>> wrote:
>>
>>     Is there a way to receive the UI refresh rate from the host?
>> Currently, no there is not, if you're using the LV2UI_Idle_Interface
>> to redraw your UI?
>>
>>     It could be helpful to now this for analyze plugs.
>>
>> I'll agree, there are many use cases where intended framerate of UI
>> would be useful.

+1

as a side-note: I recently patched jalv.gtk. With jack2 its default
plugin<>UI Atom message rate is 2Hz! Hence no matter how fast the UI
runs that's a worse bottleneck.

>> Most are for eye candy.. but your analyze plugs are a better example
>> where its needed ;)
> Eye candy is as well a other side of the strip, and I wouldn't put it
> such below then a analyzer plug.
> If LV2 ever would be a competitor to other plugin standards (and I
> really hope it will), we need a better way to redraw the UI. Be it for
> eye candy, for analyze, or for user feedback.

If you must, just don't use the Idle callback and start your own thread.
That's also what VST plugins do when they require rapid updates.

> At minimum as a plug-in developer I need to know the UI refresh rate,
> otherwise any calculation to give users a feedback running into a hole.

Why would you do timing relevant calculations in the UI thread anyway?

UI updates will never be as accurate as the timing you get in the
audio-thread.

> And it didn't differ here if it be just a eye-candy or the calculation
> of a fallback parameter from a simple VU meter.

Have a look at https://github.com/x42/balance.lv2. It includes a PPM
meter according to IEC 60268-18: 5ms integration 20dB/1.5 sec fall-off.
(NB run it in ardour or convince jalv to send messages faster than 2Hz).

Cheers!
robin