View Single Post
Old 06-13-2019, 11:25 AM
Hugh-H Hugh-H is offline
Join Date: Jun 2011
Location: Los Angeles
Posts: 182
Default Re: PT not behaving as expected when I launch and hold the 'n' key, to launch PB engi

Hello Jeffro,

We received several systems back yesterday and tested them for proper operation of the "N" key modifier to allow playback engine selection during boot without Digilink I/O attached. We engaged in this testing for a few reasons - Jeffro is attempting to help us (always a good thing), a few members of the forum have reported it works for them, and we need the ability to perform system maintenance without connecting Digilink I/O as these systems are swapped among facilities frequently.

Here are the conditions and results -

All systems - HDX2, 2x HDMadi, SyncHD
All systems - OS10.12.6
All systems - PT18.3
All systems - Digilink driver associated with PT18.3
Some systems - 2012 MacPro 8-core cheese grater
Some systems - various 2013-2015 Macs with Sonnet TB2 expansion

First test sequence - each system was tested with Digilink I/O attached to determine control timing.
N key timing -
- N key press first instance was before launching PT.
- each following test the N key press was advanced 0.3 seconds later in the launch process.
- This was continued until the N key no longer launched the Playback Engine dialog.

First test results with Digilink I/O attached -
- there appear to be four launch steps visible to the user - PT launch initialization, "hardware initialization" visible only on some systems, plugin initialization, and session initialization (I recognize there are more, this is what's visible to the casual human observer).

- The N key press can be done anytime from before launch up to the plugin initialization finishing, after which an N key press does not allow pb engine selection. This was confirmed with two of the systems that have Waves installed but the usb auth was not attached - I could delay the N press until immediately after the last Waves auth popup and still bring up the PB engine dialog.

Second test sequence - each system was tested without Digilink I/O attached using the same N key timing process. I could list the test results for each test but here's the repeatable conclusion we finally reached after observation -

- HDX2 in a cheese grater MacPro brings up the "Unable to find an audio interface...." error immediately on the "hardware initialization" step, before plugin initialization. There is no "cancel" option, only "more information" and "OK". Either way the next step is the standard "ProTools has unexpectedly quit" error and PT crashes. There is never a method for the PB engine dialog.

- HDX2 in a TB2 chassis does NOT bring up the "Unable to find an audio interface...." error, plugins initialize correctly, then the Playback Engine dialog comes up allowing selection of something else.
- If you select another audio driver PT does the standard quit and relaunch and all functions correctly.
- If you select the HDX engine without the Digilink I/O PT brings up the "Unable to find an audio interface....", hitting Cancel then reverts to the PB engine dialog.

This TB/non-TB behavior was further partially confirmed by attempting to unload the HDX kext before launching PT.
- On a TB system this results in a console error because there are two kext classes of the DigiDal kext bundle, but enough unloads to make the HDX cards unavailable and they do not show up in the PB engine dialog.
- However on the 2012 MP attempting an HDX kext unload results in an immediate kernel crash.
- Obviously the kext unload works on the system that allows PB engine selection without Digilink I/O, so that doesn't achieve much for us.

I hope these results explain what's going on. I recognize non-TB PCIe is becoming less common in the Mac world but it's very common in the Windows world and for the tiny number of folks purchasing the new MP it will become common again. Would be interesting to hear how this functions on Windows without a TB chassis using built-in PCIe slots.
It's an unfortunate thing for us because we effectively cannot do PT maintenance on some of our machines without attaching Digilink I/O, sometimes we just want to plug in some headphones and check something.

Reply With Quote