v3 AudioUnit, itself an audio unit host cannot see v3 audio units when hosted "out of process"

Question

Created Apr ’23

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Back at the start of January this year we filed a bug report that still hasn't been acknowledged. Before we file a code level support ticket, we would love to know if there’s any one else out there who has experienced anything similar.

We have read documentation (and again repeatedly) and searched the web over and still found no solution and this issue does look like it could be a bug in the system (or our coding) rather than proper behaviour.

The app is a host for a v3 audio unit which itself is a workstation that can host other audio units. The host and audio unit are both working well in all other areas other than this issue.

Note: This is not running on catalyst, it is a native Mac OS app. ( not iOS )

The problem is that when an AUv3 is hosted out of process (on the Mac) and then goes to fetch a list of all the other available installed audio units, the list that is returned from the system does not contain any of the other v3 audio units in the system. It only contains v2.

We see this issue if we load our AU out of process in our own bespoke host, and also when it loads into Logic Pro which gives no choice but to load out of process.

This means that, as it stands at the moment, when we release the app our users will have limited functionality in Logic Pro, and possibly by then, other hosts too.

In our own host we can load our hosting AU in-process and then it can find and use all the available units both v2 and v3. So no issue there but sadly when loaded into the only other host that can do anything like this ( Logic Pro at the time of posting) it won't be able to use v3 units which is quite a serious limitation.

SUMMARY

v3 Audio Unit being hosted out of process.
Audio unit fetches the list of available audio units on the system.
v3 audio units are not provided in the list. Only v2 are presented.

EXPECTED

In some ways this seems to be the opposite of the the behaviour we would expect.
We would expect to see and host ALL the other units that are installed on the system.
“out of process” suggests the safer of the two options and so this looks like it could be related to some kind of sand boxing issue. But sadly we cannot work out a solution hence this report.

Is Quin “The Eskimo” still around? Can you help us out here?

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Answer 1

FrustratedCoder OP

May ’23

Quinn?

Hopefully this little poke will get some attentiion :)

Is this a bug, is it a known bug? Our bug report has not received any reply since January? Are we going to have to file a code level request on this one?

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Answer 2

Brambos OP

Jun ’23

As far as I'm aware AUv3 plugins can not host AUv3 plugins themselves. I have looked into this several times and it has never been possible as far as I know.

Edit: I see you're specifically asking about MacOS. My experience is limited to iOS, where it certainly is not possible.

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Answer 3

ParanoidAndroid OP

Oct ’23

From our recent testing: Just to be clear, this is regarding Auv3 plug-ins loaded into Logic running on Mac OS.

Logic Pro : Intel version

Auv3 plug-ins have an option to be loaded in-process or out-of-process (AUv3 mode)
Loaded in-process an Auv3 plug-in can scan, find and load other Auv3 plug-ins.
Loaded out-of-process the plug cannot find or load other Auv3 plug-ins but can find and load v2 with no problem.

Logic Pro : M processor version

Auv3 are loaded out-of-process by default and can load v2 with no problem.
There is no option to load in-process and which appears to mean that Auv3 plug hosting other plug-ins is either disallowed or perhaps more likely just not implemented yet... .

There appear to be several minor and major issues regarding the way the M version of Logic Pro handles Auv3 and we have reported them on several occasions to no avail as of yet. Recently we filed a code support request as a last resort. If anything comes of it I'll report back!

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