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IDProjectCategoryView StatusLast Update
0007795ardourbugspublic2020-04-19 20:18
Reporterkjetil Assigned Tox42  
Status closedResolutionfixed 
PlatformWindows 10OSWindowsOS Version10
Product Version5.12 
Summary0007795: GUI freeze when changing parameters in the "a-High/Low pass Filter" plugin.
Description(see "Summary" and "Steps To Reproduce")

Steps To Reproduce1. Start Ardour 5.12
2. Create an "a-High/Low-Pass Filter" plugin.
3. Open GUI for that plugin.
4. Make sure "Plugin analysis" is visible.
5. Move a slider rapidly back and forth.
6. After a few seconds (if your computer is slow enough), GUI starts freezing.
Additional InformationTested on windows and linux, two different graphic cards, two different CPUs. Looks like it takes a lot of time to draw graphics, and when changing slider values, it can take so much time to update the graphics (probably caused by a flood of events) that the GUI freezes.

A workaround is to remove the line with "siz = lpf_chunk" from the function dsp_run.

This does not happen in Ardour 5.6.0.

(clone of issue
TagsNo tags attached.


has duplicate 0007787 closedx42 GUI freeze when changing parameters in the "a-High/Low pass Filter" plugin. Windows 10 + GeForce 



2019-08-24 14:25

administrator   ~0020752

OK. So this seems to be because the GUI thread uses 100% CPU.

- Since Ardour 5.6.0 the analysis was updated from 2048 to 8192 frames. The required CPU power for plugin analysis increased by about a factor of 4.
- a-hp/lp filter interpolates parameter changes every 64 samples, by recalculating biquad coefficients (crappy textbook DSP). This is rather CPU expensive.


2019-08-24 15:14

administrator   ~0020753

Possibly fixed in 6.0-pre0-2246-g9ce5184993

See for an explanation


2020-04-06 18:56

administrator   ~0021219

Fixed in Ardour 6.0-pre1


2020-04-19 20:18

developer   ~0023801

Issue has been closed automatically, by Trigger Close Plugin.
Feel free to re-open with additional information if you think the issue is not resolved.

Issue History

Date Modified Username Field Change
2019-08-24 13:51 kjetil New Issue
2019-08-24 13:51 kjetil Issue generated from: 0007787
2019-08-24 14:00 x42 Relationship added duplicate of 0007787
2019-08-24 14:25 x42 Note Added: 0020752
2019-08-24 15:14 x42 Assigned To => x42
2019-08-24 15:14 x42 Status new => feedback
2019-08-24 15:14 x42 Note Added: 0020753
2019-08-24 15:17 x42 Relationship replaced has duplicate 0007787
2020-04-06 18:56 x42 Status feedback => resolved
2020-04-06 18:56 x42 Resolution open => fixed
2020-04-06 18:56 x42 Note Added: 0021219
2020-04-19 20:18 system Note Added: 0023801
2020-04-19 20:18 system Status resolved => closed