Racks and plugins with variable inputs

[pough]

TL;DR
1. Is changing the number of inputs after loading a plugin something that should technically work?
2. If not, can we specify the number of inputs before loading a plugin?

Someone over on Facebook was asking about using Voxengo's free SPAN plugin in Waveform. It theoretically has multiple inputs and can allow you to view spectrum information for multiple tracks at the same time. Unfortunately, there's something funky about setting the number of inputs. It doesn't update the internal routings within the SPAN plugin. (Actually, it sometimes does but goes in the opposite direction.)

The plugin validator is able to see the optional buses (VST 2.4 version of SPAN)

Code: Select all

Starting test: pluginval / Listing available buses...
Inputs:
	Named layouts: Mono, Stereo, LCR, Quadraphonic, 5.0 Surround, 5.1 Surround, 7.0 Surround, 7.1 Surround
	Discrete layouts: Discrete #1, Discrete #2, Discrete #3, Discrete #4, Discrete #5, Discrete #6, Discrete #7, Discrete #8
Outputs:
	Named layouts: Mono, Stereo, LCR, Quadraphonic, 5.0 Surround, 5.1 Surround, 7.0 Surround, 7.1 Surround
	Discrete layouts: Discrete #1, Discrete #2, Discrete #3, Discrete #4, Discrete #5, Discrete #6, Discrete #7, Discrete #8
Main bus num input channels: 1
Main bus num output channels: 1
All tests completed successfully

I have loaded SPAN (VST 2.4) in FL Studio and you get 4 stereo inputs, which allows you to display the spectrum for multiple tracks. In Waveform, nothing I do in the Rack settings results in SPAN believing there is anything other than a single stereo input.

So my questions (simplified above) are:

Does the VST spec allow for the changing of inputs, meaning the Voxengo plugin just isn't coded to be able to handle changing inputs properly?

Is there a way to specify the inputs when a plugin is loaded? It looks like FL Studio loads SPAN with max inputs and then just ignores most of them unless I decide to use the extra input. It looks like Waveform loads SPAN with a default layout that includes one stereo input.

Do we have examples of plugins that handle input changes correctly? It looks like Waveform's Racks have the ability to change the inputs for a plugin but so far I've only tried SPAN and it doesn't seem to work.

If changing the inputs is part of the VST spec, is it in both VST 2 and VST 3?

[pough]

There's nothing like writing things down to make you think of new possible solutions. It seemed like SPAN doesn't like to change input settings but it's fine loading input settings. I made a Rack, added SPAN, changed the number of inputs and outputs to 4 (2 stereo pairs.) It didn't work at first, but after saving the edit then closing and re-loading, SPAN had 4 inputs and outputs internally.

[Kang]

Yeah I see what you're saying. it definitely feels like it should work without having to restart.

I did a few tests with elysia mpressor. VST3 I 'think' works normal. The VST2 sidechain version I thought normally had "unknown" inputs that I used for sidechaining (without setting them up). Now I have to set up the 'discrete' inputs and 1+2 act as normal R+L and 3+4 control the sidechain and yes indeed it does not work unless you restart it. So I believe it's probably an issue in Waveform, possibly just with VST2. Also explains some issues I was having, so thanks for noticing that!

Side note: Cool trick with SPAN. I can't figure out how to get more than two spectrums at a time. I can combine multiples inputs into one spectrum, but are you able to get more than two seperate spectrums ('colors', if you will)?

[pough]

Yes but I had to change some settings in SPAN.

1. Open Routings and make sure 3 and 4 are set to G-2 in the Groupings.
2. Set the Underlay to G-2

[Kang]

I was able to figure that part out with two spectrums, like in your pic. I was wondering if there was a way to get even more spectrums using the other available inputs on SPAN? I can get all 8 inputs to work and they register, but you can only combine them with other inputs to have two separate spectrums showing, as far as I can tell (haven't totally figured this routing out yet). It would be awesome to have a single SPAN view of drums, guitar, bass, vocals busses all showing their own spectrums.

When you said 'multiple' I though maybe people were doing more than two and I was missing something, but I think I just misunderstood.

Anyhow, thanks again for bringing this to my attention. Hopefully the devs take care of it.

[pough]

You can have multiple groups set up, but can only have two showing at once. That's true even for the pay-for Plus version.