Calf Reverb installed and "seen" by Ardour, but an old session yelps that it's missing and loads a stub instead

As in the topic, I have an old 6.x session that I just tried to revitalize, and it won’t load Calf Reverb (LV2) - it says that the plugin is missing, and loads a stub instead.

However Calf Reverb (LV2) is absolutely positively installed, the plugin manager lists it, lv2ls lists it, etc.

What gives?

For me is working fine with Ardour-7.4 compiled for openSUSE but does not load with official package. Not the first time that I see this kind of problems. This is why I prefer Ardour from distro repo instead of official binary.

This sounds suspiciously like a URI ID changed somewhere. Does it load without issues in A6?

Can you give me the output of lv2ls and the output of lv2info if run on that plugin? Also may need you to post your session file (Just the session file itself IIRC, probably best to post it somewhere else and link to it here).


I think it’s a dependency issue, I’ve tried with the current nightly debug build which is 7.5.0 as it says.
This is the error message I get:

lilv_lib_open(): error: Failed to open library /usr/lib64/lv2/calf.lv2/ (/lib64/ undefined symbol: g_string_free_and_steal)

As Daniele said, our locally compiled binaries instantiate the calf plugins just fine.

Hmm I am seeing references online to Pango requiring updated glib here. So not really an area I know to well, but I suspect this comes from Calf plugins using GTK, Ardour is bundled with GTK and a specific version of glib, where calf utilizes pango that requires a new version but since it is instantiated in Ardour’s environment and utilizes ardour’s glib it doesn’t work.

I am sure Robin or Paul will be along to correct me if I am off base here.

That being said it is another argument that plugins should be entirely self contained and statically compiled, and that GTK/Qt may not be good choices for plugin UIs.


Plugins are supposed to be self contained and not rely on external libraries which can conflict with other plugins or the plugin host.

Calf is notorious for getting this wrong in addition to having various DSP issues. The reverb is known to produce loud speaker killing pops, all calf multiband introduce phasing issues and distortion, controls are not interpolated and cause zipper noise, and the GUI visualization is misleading and does not show what the DSP does,…
I highly recommend to avoid calf plugin-suite for pro-audio. Check out LSP-plugins for example.


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