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Old 01-11-2023, 11:35 PM
MarkH MarkH is offline
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Default HDX External Insert - Plugin Delay Comp timing

Hi all, I'm attempting to use external hardware inserts on my HDX2 system. I'm using an Antelope Galaxy 64 which has four Mini Digilink ports. I've setup 2 Aux tracks, each with Click II. On one of the tracks I am routing to analog out 9 on my Galaxy, and back in on input 9. There is no hardware in between. I'm just running analog DB25 output 9-16 to DB25 input 9-16. In Pro Tools Ultimate when I insert external I/o for one of the click tracks there is a slight phasing. I was hoping with the Galaxy 64 setup to HDX Auto Delay Compensation, Pro Tools would take of this automatically. I realize it's not a genuine Avid branded interface. Antelope provide Delay Compensation Settings where you can manually adjust which locks it in 99.9%. I don't think routing to external hardware and back would be a problem unless it's parallel compression and some of that faint phasing sound would be a problem. My question is with genuine Avid interfaces (MTRX, MTRX Studio, Carbon, Analog HD 16 I/O) is it 100% solid timing even when using parallel compression? Trying to figure out if I set my expectations to high or if the issue is just the Antelope interface. Thanks!
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Old 01-12-2023, 12:18 AM
Darryl Ramm Darryl Ramm is offline
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Default Re: HDX External Insert - Plugin Delay Comp timing

What you are seeing is expected behavior, but finding interfaces with claims of the same latency is likely not worth worrying about, just fix it in your session. You should be able to fix this as well as you can get with any Avid interface(s).

When you say "insert external I/O" you mean you are just enabling the H/W insert on that track but the insert is physically just a straight through cable?

Pro Tools is correcting for whatever latency the genuine Avid box has that your box is emulating. Not all vendors' Digilink interfaces deliver that same latency the Avid box they emulate. If your box has less real latency the signal will be offset negative time compared to others, if your box takes more time to do a conversion it will be shifted to positive time compared to other signals. All this happens once you turn delay comp on which is required to correct for hardware inserts.

You can manually adjust the track delay comp +/- setting to correct this. Probably better to null out any latency compensation errors there then in the Setup>I/O>Insert settings which is really intended to correct for latency in the outboard insert box. And you can't set those insert latencies to negative time so it won't handle many cases.

You need to make one measurement comparing a transient that you send to the H/W insert to the return signal. Measure the difference accurately in samples (you should be able to measure that latency to ~one sample accuracy) and apply that in the +/- field for every track that has a H/W insert on it using that same box. You need to change this only if you change the sample rate. No need to rely on any vendor latency specs... and I never would when I have a tool in front of me that can measure those values, and let me set them, and confirm they are correct to a sample or so). And this latency is physically fixed and cannot change (unless you change sample rates).

Yes Avid could make all this easier with a ping function, and UI/UX improvements, and it's embarrassing for them that Pro Tools is so bad here, but add that to a list of other latency comp bugs including with Carbon... the place needs work. But, big but... nothing here should be too difficult to do to get great results. When doing this test do it all first with no plugins and very simple session, you don't want to be chasing other plugin delay comp or phase change issues. Just start with one or a few tracks and H/W inserts on an audio track. As simple as possible.

There however are bugs in delay compensation, one that you can run into at least on native system with a H/W insert following a plugin. This one I'm thinking of causes very large errors in delay comp (like 2k or 4k samples) on inserts when LLM is enabled. I'm not sure if it could ever show up on a HDX system. I've posted about that on DUC multiple times, if you are seeing small sample offsets you should be fine and be able to adjust them as expected. Yes there might always be other bugs, but I've had no problems correcting multiple different interfaces like this (most are not Digilink, but it's the same thing).
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Old 01-12-2023, 01:31 AM
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Farhoof Farhoof is offline
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Default Re: HDX External Insert - Plugin Delay Comp timing

Quote:
Originally Posted by MarkH View Post
I've setup 2 Aux tracks, each with Click II. On one of the tracks I am routing to analog out 9 on my Galaxy, and back in on input 9. There is no hardware in between.
Don't output the aux to an output unless it's your speakers, but instead create an insert in the IO settings using these inputs/outputs, and use this as an (i/o) insert on the aux. Protools handles outputs and inserts different.
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Old 01-12-2023, 01:52 AM
Darryl Ramm Darryl Ramm is offline
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Default Re: HDX External Insert - Plugin Delay Comp timing

^^^ I maybe misread you were using H/W inserts. Use H/W inserts as they are intended than all I said applies.
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Old 01-12-2023, 06:03 PM
MarkH MarkH is offline
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Default Re: HDX External Insert - Plugin Delay Comp timing

Thanks for the replies. I believe I figured it out and the Galaxy has the same issue as the Focusrite Red HD, but it's fixable on the Galaxy. The HD part of the device is emulating a Digi HD 16x16 "DIGITAL" I/O, not 16x16 Analog I/O, and when using the interface (Red HD or Galaxy) with analog I/O the "Automatic Delay Compensation" calculation is off by 22 samples (in a 48k session). Unlike Red, Antelope has an HDX tab in their Control Panel and lets you switch Delay Compensation for HDX from Auto to Manual and adjust the HDX latency on each of the 128 channels individually. This resolves the issue. Still not as clean as Apogee interfaces which have perfect calculation but at least there's a way around it compared to the Focusrite Red where there's no way to make an adjustment in the Red software.
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