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IDCategoryLast Update
0007643bugs2018-07-24 13:13
ReporteralexmitchellmusAssigned To 
Status closedResolutionfixed 
PlatformArch LinuxOS4.17.3OS Version4.17.3
Product Version5.12 
Fixed in Version 
Summary0007643: Faust generated LV2 & VST exhibit strange slider behaviour with AutoGenerated GUI
DescriptionWhen changing the values of Faust plugins with the built-in Ardour plugin GUI, it is hard to change the value with the mouse.

I have made a video of what it looks like:

The video was made with the LV2 version of the plugin, however the same issue is present on the VST version of the same .dsp code.
Steps To ReproduceI tested one of the tutorial Faust FM synth patches:

carFreq = 500;
modFreq = 30;
index = 100;

process =
  os.osc(carFreq + os.osc(modFreq) * index) <: dm.zita_rev1;

I used the command line to build the above faust code:
$faust2lv2 myplugin.dsp
$faust2faustvst myplugin.dsp

I then placed the lv2 into: /usr/lib/lv2/ & the VST into: /usr/lib/vst/
Additional InformationI tested the same plugin (the LV2) with Qtractor, and this issues was not present in that software, I could easily change the values with the GUI.
TagsNo tags attached.



2018-07-04 10:23


FM_Synth.dsp (139 bytes)


2018-07-04 10:29

reporter   ~0020323

Last edited: 2018-07-04 10:30

View 2 revisions

NOTE: I used the git version of Ardour (as I was working on some MIDI note code ideas at the time) for the video. (an astute viewer would probably be able to tell the strange MIDI note colors).

However I also tested Ardour 5.12 (which had the same issue).

There is no issue with automating the parameters, they change correctly, this issue is only about mouse control.

Also after a bit more research, there is apparently no issue with manually created sliders (if I were to put sliders into the Faust code myself), the sliders that are in the video are all from dm.zita_rev1. So I am not sure if this is a problem with 'zita' or Ardour, or Ardour's ability to control sub-module GUI's of Faust .dsp code.


2018-07-04 12:32

administrator   ~0020336

I cannot reproduce this (also git,6.0-pre0-781-g870fe055c). What version of FAUST and its stdlib are you using?

Ardour is one of the few LV2 hosts that honors "rangeSteps" and enforces the min/max parameter range.

Can you check the generated .ttl file if it matches:
    ] , [
        a lv2:InputPort ;
        a lv2:ControlPort ;
        lv2:index 2 ;
        lv2:symbol "Low_RT60_2" ;
        lv2:name "Low RT60" ;
        lv2:portProperty epp:hasStrictBounds ;
        epp:rangeSteps 70 ;
        lv2:default 3 ;
        lv2:minimum 1 ;
        lv2:maximum 8 ;
        units:unit [
            a            units:Unit ;
            units:name   "s" ;
            units:symbol "s" ;
            units:render "%f s"
        ] ;
    ] , [


2018-07-04 15:09

reporter   ~0020338

I am using Faust: Version 2.5.23. My .ttl (in that part) is exactly the same.

Possibly this could have something to do with my OS? (Using Arch Linux?)


2018-07-24 13:13

reporter   ~0020362

x42 was able to look into this issue, and it looks like its resolved! Yay! (other than a few fixes that have to happen on the Faust side of the fence)

Issue History

Date Modified Username Field Change
2018-07-04 10:23 alexmitchellmus New Issue
2018-07-04 10:23 alexmitchellmus File Added: FM_Synth.dsp
2018-07-04 10:29 alexmitchellmus Note Added: 0020323
2018-07-04 10:30 alexmitchellmus Note Edited: 0020323 View Revisions
2018-07-04 12:32 x42 Note Added: 0020336
2018-07-04 15:09 alexmitchellmus Note Added: 0020338
2018-07-24 13:13 alexmitchellmus Note Added: 0020362
2018-07-24 13:13 alexmitchellmus Status new => closed
2018-07-24 13:13 alexmitchellmus Resolution open => fixed