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IDProjectCategoryView StatusLast Update
0007707ardourbugspublic2018-12-18 08:54
Reportergarvalf Assigned To 
Status newResolutionopen 
PlatformLinux + kxstudioOSLinux Mint 19OS Version4.15.0-20-lowlat
Product Version5.12 
Summary0007707: many Xruns when running LV2 plugins with many parameters
DescriptionI am running Ardour on a high end computer, and I noticed when running a LV2 instrument with many parameters, even if the plugin is not too loaded, Ardour with produce some Xruns.
Steps To ReproduceInstall ADLplug ( (970 parameters) or DrumSynth (2500 parameters).
Configure Ardour and Jack for low latency (2.8 ms for example).
Playing or recording live with produce many Xruns and noise artefacts.

The adlplug lv2 synth running as stand alone is working fine. In LMMS, used as carla baypatch, there are still some xruns, but less than in Ardour.

There are maybe some possible optimisations from the Ardour side.
Additional InformationThere are many parameters in adlplug because all the basic parameters are replicated for 16 (midi) tracks.
TagsNo tags attached.



2018-12-15 17:43

administrator   ~0020531

This is a known issue.

There was a some small optimization in 51e33796f1 (git) a month ago, but Ardour assumes that every parameter may be automated and checks all automatable parameters on every plugin run.

Ideally automation would be pre-calculated and only actually automated or modulated parameters be evaluated in realtime context.

However a LV2 plugin with > 900 control ports make no sense at all. For LV2 prefer properties and message-passing on demand. That way you can use millions of control parameters.


2018-12-18 08:41

reporter   ~0020540

Last edited: 2018-12-18 08:48

I found the impact of patch 51e33796f1 to be quite significant.
I ran some sessions between Ardour 5, 5+patch, and 0d55dad of 2018.12.17.

Adding one plugin instance into an empty session, I observed DSP load to increase as indicated:

5.12 : 11% ? 40%
5.12 patched : 11% ? 22%
6 : 12% ? 16%

Configuration was "Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz" with Jack at Fs=48k Bs=64

Issue History

Date Modified Username Field Change
2018-12-15 17:10 garvalf New Issue
2018-12-15 17:43 x42 Note Added: 0020531
2018-12-18 08:41 jp.cima Note Added: 0020540
2018-12-18 08:48 jp.cima Note Edited: 0020540