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Applying audio unit to system input

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Applying audio unit to system input

Postby Marcus Bointon » Sun Apr 05, 2020 6:10 pm

There are a ton of audio unit hosts, and they can all apply audio units to the audio they handle, with one big omission: the system sound input.

I want to be able to insert one or more audio units in front of apps like Skype & Zoom, but I've not found a good way to do so. It's possible to set up this flow using the standard AU Lab app supplied with macOS, however, it's really unreliable and can't usually survive sleep or reboot without breaking and requiring setting up again.

I'm thinking along the lines of Rogue Amoeba's Soundsource, which does almost everything except this.

I expect there's some complicated solution involving soundflower & Jack and some minimal AU host, but I find things like that so fiddly and fragile. It's a shame that there's not a simple "insert audio unit" in the system sound control panel.

Can anyone recommend a reliable, straightforward solution for this?
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Re: Applying audio unit to system input

Postby desmond » Sun Apr 05, 2020 6:26 pm

I always use Rogue Amoeba's Audio Hijack for this stuff.

You can hijack, route, and add plugins to any audio or app audio source, and it's bulletproof and easy to use.
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Re: Applying audio unit to system input

Postby Marcus Bointon » Sun Apr 05, 2020 9:51 pm

I've played with that before - Unfortunately it doesn't quite do it. It can't target either the system input or an application as an output, only as an input. The only way I can see that working is to connect it up to the system input, process it through Audio Hijack, direct its output to Soundflower, and then select that as an input to whichever apps I want it to go to.

Soundflower isn't supported any more, but I just discovered that Rogue Amoeba's Loopback provides the same kind of virtual audio device that allows this. Since it plays nicely with Audio Hijack, I might give that combo a go.
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Re: Applying audio unit to system input

Postby Marcus Bointon » Sun Apr 05, 2020 9:52 pm

Yikes, but $150 for the bundle of things I want to be invisible seems a bit steep...
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Re: Applying audio unit to system input

Postby desmond » Sun Apr 05, 2020 10:00 pm

Marcus Bointon wrote:I've played with that before - Unfortunately it doesn't quite do it. It can't target either the system input or an application as an output, only as an input. The only way I can see that working is to connect it up to the system input, process it through Audio Hijack, direct its output to Soundflower, and then select that as an input to whichever apps I want it to go to.

Ok, I have a better understanding of what you are trying to do. So if you have an app (eg Skype) which lets you choose an audio input, and you want to put a plugin before it, then yes that's a problem as there is no way to put plugins inbetween the system input to an app that requests that input.

Marcus Bointon wrote:Soundflower isn't supported any more, but I just discovered that Rogue Amoeba's Loopback provides the same kind of virtual audio device that allows this. Since it plays nicely with Audio Hijack, I might give that combo a go.

In this case, then you are correct in your thinking that you would need to create a virtual audio bus, and Loopback, Soundflower or Blackhole should do the trick, in conjunction with Audio Hijack (as I don't think Loopback can put plugins on virtual audio busses) - with Loopback being the nicest, though not exactly inexpensive. Your input gets routed, through a plugin, to the virtual audio bus you create, then you set that bus as the input to whatever app you want it to receive from.
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