Quark plug-in for decoding Quad (QS)

Studio Audio Units and VST3
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There is a free plug-in named Quark which can decode Quadraphonic QS signals encoded in stereo files. There are many QS encoded recordings available from streaming services, such as Qobuz. If we have a 4 speaker system we can enjoy these in Quadraphonic sound by running them through this plug-in.

Examples include many artists I love, such as Alice Coltrane, John Coltrane, Pharoah Sanders and Santana, just to name a few. They tend to be mainly from the early 70’s when there was a commercial push for Quad. A list of known QS encoded CDs, can be found here

Unfortunately when it comes to judging if you are, indeed, getting true Quadraphonic from these titles, via the Quark plug-in, you will have to judge by ear, because as Richard Brice of pSpatial explained to me, “the milk is mixed in with the coffee”. So you have to listen for discrete elements from your rear left and right speakers, to be sure you’re getting bone fide Quad. However, you will not do any harm if you end up running a plain stereo file through this plug-in and it may even sound a little better.

The reason I’m posting about this here is that it can’t work in Audirvana. That may not be a fault of Audirvana though. The reason is if you start off with a Stereo source file and feed it into a plug-in, which produces 4 channels, how do you know where the rear left and right channels should be routed?

So I’m sending Audirvana’s output to Blackhole and using a pre-compiled Juice plug-in host app to run the 4 channel outputs from Blackhole into Quark and then routing them to the appropriate corresponding channels of my final output device.

In a 5.1 or higher set-up such as with my Exasound multi-channel DAC, the left and right rear channels are 5 and 6. This can’t be assumed though.

If you try to use Quark in Audirvana right now, it can’t be configured. Clicking on the “Configure” button does not cause its settings window to appear.

So I’m posting this here as a general question for @Antoine and others. Could such a plug-in that can produces more channels of audio data than are fed into it, be made to work in Audirvana? Perhaps if the plug-in developer included a way of indicating which channels of the output device each signal should be mapped too?

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I know that Mitch Barnett @mitchco worked with @Antoine to get some multichannel solutions working with the HangLoose Convolver a few months back… Maybe Mitch will comment here…

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Thanks. I posted this really not just about the Quark plug-in; but about multi-channel plug-ins, in general. I don’t know if @mitcho’s solutions involved a different number of input channels as output channels, as this Quark plug-in does. There could also be other plug-ins that have more in’s than out’s, or vice versa, and it’ll be interesting to know if they can be made to work.

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You might take a look at the HangLoose Convolver documentation and even try it as there is a 14 day trial version available… And contact Mitch directly with any specific questions…

Note that it is a stereo and multichannel convolver…

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Hi @Ddude003, @soundgals

In the case of HLC, the convolver .cfg file that is loaded into the convolver specifies the number of convolvers, channel routing/mapping, summing, etc. E.g. 2 channels in and 6 channels out:

However, if one looks closely at the pic, there are actually 8 HLConvolver meters and Audirvana says 7.1 output (i.e. 8 channels). It is only because of the convolver .cfg file that enables the channel mapping, but the convolver I/O will default to the total number of DAC channels reported by Audirvana.

I would assume your Exasound DAC is reporting 8 channels. As you have found out, it is straight pass through in Audirvana as there is no way to specify the number of channels required or mapping.

Most “Hosts” typically configure the plugin with the number of I/O channels required, like you can with the APH app you are using. Also, most hosts allow I/O channel mapping in one form or another. In the case of APH, you are “wiring” the I/O from the host to plugin.

As shown in the VST3 documentation: Bus Arrangement Setting Sequence - VST 3 Developer Portal

Looking at the sequence diagram, the 'host" is responsible for setting the number of I/O channels required for the plugin. The plugin either accepts or rejects that. In the latter case, the host then queries the plugin for its channel I/O (i.e. bus arrangement) and then host the accommodates that and offers those choices to the user. It is a two way communication between Host app and plugin.

This host API is not implemented in Audirvana. There are additional Host interfaces (AU for Mac) that would need to be implemented to take full advantage of what each plugin can offer.

Hope that explains.

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That explains it all very clearly, thank you, and it confirms what I suspected, which is that Audirvana cannot support all VST3/AU plug-ins. Hopefully @Antoine will be able to update us on any intention to fully implement the host API in Audirvana.

It’s great that Audirvana as a player does support VST3/AU plug-ins. Until the host API is fully/properly supported though, I think there should be something in Audirvana’s interface/documentation to make it clear that this type of plug-in, which needs I/O channel mapping support, cannot be used.

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Thank you Mitch, @Mitchco, for sharing your time and expertise with the Audirvana community… :+1:

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