VST3 problem in Ardour 6

1

I just discovered that none of my VST3 plugins work in Ardour (latest 6.9). Audio is coming into the plugins (as shown on meters, etc.) but the processed audio is not being returned to the DAW. Instead, the output seems to be a direct copy of the input - like the plugin is perpetually bypassed. It looks like the plugin is working but it’s not doing anything to the sound.

The VST2 builds of these same plugins do work in Ardour - and so do other brands of VST3 plugins - so this seems to be an issue somewhere in IPlugVST3.

I noticed @ftw came across this issue “not getting any output from it in a DAW (I’m using Ardour)” in another thread.

I have not seen this problem in any other DAW, only Ardour, but I am concerned there could be some latent issue here that should be addressed.

What could be causing this and how to troubleshoot/where to look?

BTW - I just tried IPlugEffect.vst3 and it does not work in Ardour either. The gain control has no effect on the sound.

2

I’ve done some digging on this and here is what I have found so far:

With a simple “2-2” only config. loaded into a stereo audio track in Ardour,

IsChannelConnected(ERoute::kInput, 0);  both report TRUE
IsChannelConnected(ERoute::kInput, 1);

IsChannelConnected(ERoute::kOutput, 0);  both report FALSE
IsChannelConnected(ERoute::kOutput, 1);

NOutChansConnected() reports "0"

This confirms what I am hearing and seeing. Audio is getting into the plugin but is not being returned back to the DAW.

The VST2 version reports TRUE for all 4 pins and works properly.

Other brands of VST3 plugins I have tested work in Ardour so this is not a blanket Ardour VST3 issue. Meanwhile, this same VST3 plugin works in every other DAW I have tested in. So it appears there is something peculiar to Ardour + IPlug.

What could be the problem here and where to look for the cause/fix?

3

@olilarkin - I just saw that you added the check and exception for this to the IPlug master on GitHub. Thank you! Since Harrison Mix Bus has become popular, and seems to be related to Ardour, this workaround will likely help many IPlug VST3 developers at some point.

Yes, IMO, this is a bug in Ardour. Every VST3 plugin I have checked in Ardour - by every developer - reports the following error:

[Info]: VST3: \ error getting busInfo for bus: 0 rv: 0, got type: kMain
[Info]: VST3: \ error getting busInfo for bus: 0 rv: 0, got type: kMain

AFAIK, bus 0 is the main bus so I don’t understand why this error message. Some VST3 plugins work and some don’t.

I have reported this issue to the Ardour team as well.

Thank you!

1 Like
4

It seems that Mixbus doesn’t have the UI problem that I see in Ardour (very low framerate in iPlug UI, wrong colours). Not sure why that is, or how different they are

5

Yes, Ardour seems to be one the troublesome DAWs that does things their own way. “Fruity Loops” is another one, IME.

We can spend a lot of time troubleshooting and developing conditional tweaking for these DAWs but I’m never sure where to draw the line and just say “it’s their fault” if it works everywhere else.

6

It turns out the patch solves the problem with “2-2” configuration plugins in Ardour but there is still something very wrong in Ardour’s VST3 interface. I have a plugin that supports multiple stereo outputs using a “2-2.2.2” configuration that works fine everywhere else but is a total I/O mess in Ardour. The VST2 version works perfectly but the VST3 version only shows up with 4 output pins. All of the outputs produce loud white noise when the transport is stopped which does not happen in the VST2 version.

I’m going to call this one “Ardour’s fault”. The plugin works fine in every other DAW I’ve tested.