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Old 11-29-2020, 11:53 AM
gandlz gandlz is offline
Join Date: Mar 2011
Location: Austria
Posts: 63
Default Compensate Input/Output Delay with external converters – not H/W Insert delay!

Compensate Input/Output Delay with external converters – not H/W Insert delay!

I found this topic discussed in a few threads but mostly there are only a few people understanding what’s meant and often it’s confused with the ability of H/W Insert delays.

Although my personal tests where made with Pro Tools 10 HD with 192 I/O and Pro Tools 12 native with RME Fireface UC, there is absolutely no different behavior in most recent versions with new Avid I/Os, neither HDX or native.

The problem explained:
Enable Delay compensation and also check the according options in I/O Settings (input and output).
Playback an audio track (1kHz square) on 192 I/O analog output looped to 192 I/O analog input and recorded on new track. This track is perfectly in sync with the original track.
Do the same but record it through any external converter connected via AES or ADAT to your 192 I/O. The result will be too late.
If you go one step further and output the original track through an external converter connected to 192 I/O via ADAT or AES you will get additional delay.

Focusrite Octopre MKII dynamic via ADAT: 16 samples late from 192 I/O, 34 samples late from Octopre
Universal Audio 4-710d via ADAT: 14 samples late from 192 I/O, 32 samples late from Octopre
Universal Audio 4-710d via AES: 12 samples late from 192 I/O, 30 samples late from Octopre
Octopre analog out to 192 I/O analog in: 18 samples late

How did I recognize this as an issue?
I wanted to use my Octopre analog outputs for the Cue-Mix outputs. I had a singer and the microphone preamp was connected to the additional line inputs on the 4-710d. This makes the vocal track 30 samples late as explained above. This is 0,68ms at 44.1kHz and in fact is not acceptable. The timing issue was recognized by everyone in the studio.

In general:
You can change the 192 I/O in this example with any other interface (also native) which has it’s own analog and digital inputs for use with external converters. In native situation the ASIO driver tells Pro Tools about the input and output delay created by DAC/ADC of your interface and this is compensated correctly. But if you use external converters connected to your interface, the driver has no idea about the time your external converter needs for conversion and therefore the tracks will not be in sync.
Pro Tools HD and HDX know about the delays of Avid interfaces and compensate correctly but have also no idea about external converters.

Delays change when disabling I/O compensation in I/O settings or disabling Delay compensation at all (or any possible combination). That shows that every settings adds a fixed amount of samples to compensate.

The solution would be...
...to make the amount of samples compensated for "after recording pass" (as said in the I/O Settings window) variable! In my situation I would have to give all Octopre outputs 18 samples of additional compensation. And so on for the different kinds of inputs I have. I think about one more column in the I/O Settings window, where we can just add this amount of samples.

This is really annoying…
…and I tested a lot, and also tried to develop some workflows. But you always have to nudge and if you combine a few converters the situation is really complicate and you miss to focus on the overall work you have to do. And also you cannot use spot function with original time stamp as far as this timestamp is what you really want.

So I really bought a fourth 192 I/O and changed my 4 stereo Cue-Mix to those analog outputs. So everything is heard at the same time.
I don’t use the 8 channels ADC on the 4-710d anymore and connected it to the 8 inputs of the fourth 192 I/O.
ADAT Octopre is used for gate triggers at the moment. I put these tracks 3000 samples ahead to work with my sidechain gates, so original timestamp is not important.
So all four 192 I/O do only 8 channels of I/O (except the last one with the Octopre) and I need a fifth if I buy one more preamp!

What I also noticed during testing:
when looping AES output to input the recorded signal is 15 samples too early.

Post-Fader sends are compensated same as explained above but Pre-Fader sends are compensation different and recorded signal is additional 6 samples late. Adding any Plug-In inserted on Master-Fader of that PRE-Fader send, makes the recorded signal 4 samples late. (Maybe that’s different on newer Pro Tools versions?!)

Realtime SRC on ADAT inputs when working with higher sample rates adds additional 28 samples delay.

What can we do - Metaplugin:
For making all outputs synced (Avid IOs and external Converters, and solving the PRE-Fader Bug described above) you can use something like Metaplugin by DDMF. Sadly I didn’t find anything else.
The idea is to add this insert on the Master-Fader and define a Plug-In-Latency that does not exist.
For example on my Cue-Mix outputs (ADAT-to-Octopre) I would define 18 samples of latency (as mentioned above) or 24 samples (additional 6 samples) if the Cue-Mix is PRE-Fader.
As the result, all other outputs are delayed by 18 (24) samples and therefore in sync with the Octopre-Output. As far as this playback is recorded to a new track using the 192 I/O, it is in sync.

The problem with Metaplugin:
Metaplugin itself adds heavy latency additional to the fake-latency you define and therefore it is not usable for realtime monitoring. Also it is only available as native and not as DSP Plug-In, which means that your Master-Fader needs 2 additional voices for mono (4 for stereo).
I did not find any other Plugin to define a fake-latency and metaplugin is pretty overloaded for just doing this. A simple DSP-Plugin just doing this would be the solution for making outputs in sync.

As far as you count Metaplugin as a solution for outputs (I would not recommend this) there is still no solution for inputs.

I hope you got what I wanted to show up with this writing. Just think about your individual recording situation and the different analog and digital inputs you are using on your main interface (either its Avid or any third party native interface) and be aware of, that different inputs have different conversion latency which is not compensated in Pro Tools.

You may say these are only a few samples, but this is when doing loops. In real life you have physical distances adding latency. Distance from Headphone or Monitor to ear, from instrument or speaker to microphone. So you may end up nudging tracks more because of other reasons.
But I think we should start up from a perfect professional solution and be able to mess it up later.

I’m excited about any response (if any) to this topic either technical input, workarounds or solutions, or why this is not discussed anywhere and therefore not recognized as a problem.
Or why in 2020 we are not able to record through different converters and have it in sync in our timeline because we are not able to define the latencies of the converters used.

Kind regards,
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Old 11-29-2020, 01:18 PM
Join Date: Dec 2004
Location: Gent, Belgium, Europe
Posts: 411
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

Well, I hate to be the elephant in the room, but you basically answered your own question. Pro Tools can not know or compensate for any latency induced by any external AD/DA and/or processing. As long as you use AVID hardware, it will, but that's only compensating AD/DA conversion latency. If you would send your signal out of an HD I/O, route it around the world, and record back in, you would get something like a 133ms delay. HW inserts allow you to specify this round trip delay (e.g. if an effects box, or in your case, your additional interface, is inducing extra latency). But for regular I/O you'll have to adjust yourself.
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Old 11-29-2020, 02:26 PM
gandlz gandlz is offline
Join Date: Mar 2011
Location: Austria
Posts: 63
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

Well, I read exactly the same somewhere else "Pro Tools can not know …"
But I know the latency of that external device, so please give me the possibility to set it within the I/O Settings. Is this really so hard to make it work? I would really like to see an official statement why this is not implemented just as the H/W Insert Delay. And again, the H/W Insert Delay is not usable for this issue.

Let me tell you something more:
When “compensate for input/output delay after recording pass” are both unchecked, the 192 analog to analog is 86 samples late while 192 analog to 192 ADAT through Octopre is only 40 samples late. Seems that the Octopre conversion is much faster.

When you enable delay compensation step by step you will notice that the checkmark “compensate for output delay after recording pass” will make a difference of 22 samples for both loops. But “compensate for input delay after recording pass” makes a difference of 64 samples for the analog input and only a difference of 2 samples for the ADAT input. And this makes the Octopre 16 samples late.

So why can we not just change that 2 samples to 18 samples and the result would be in sync?!
I wish some programmer could tell me the file I need to open in a hex editor and change a few lines to make this happen.

I also found a feature request from 2009 about that…
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Old 11-29-2020, 03:24 PM
Join Date: Dec 2004
Location: Gent, Belgium, Europe
Posts: 411
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

No other DAW will offer you this option. The only real solution here is to either 1. use all AVID hardware 2. manually compensate your tracks after record pass.
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Old 11-29-2020, 03:47 PM
gandlz gandlz is offline
Join Date: Mar 2011
Location: Austria
Posts: 63
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

One reason more to implement this!

I just read the manual of the new Avid MTRX interface. There’s a section describing timestamping of the inputs and telling you that analog input conversion is compensated to be in sync with the digital inputs. But it seems that the digital inputs are used as reference and any possible conversion externally is just ignored. (just shortly summarized)

In fact they should tell that those great 16 channels of AES inputs may not be in sync with any analog input card in recording situations when you use external converters.

I mean, it's all about a simple computing task, nudging audio within a region after recording pass by an amount according to its input type.
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Old 11-29-2020, 04:29 PM
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Top Jimmy Top Jimmy is offline
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Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

Not exactly a new issue.

The suggestion on Ideascale never got much traction.
James Cadwallader

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Pro Tools Ultimate 2021.3, HD Native, Focusrite Red 8Pre (Mac)
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Old 11-29-2020, 05:01 PM
Darryl Ramm Darryl Ramm is offline
Join Date: Nov 2010
Location: USA
Posts: 14,935
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

It's a pity that compensate after recording pass is an Ultimate only feature, you would think that Avid would care that integrity of the signal is actually important in all products. And yes then even this could be done much better wit non-Avid interfaces, CoreAudio and ASIO expose latency information for an interface, there should be no reason to have to enter this stuff manually, at least when using converters built into an interface.
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Old 11-30-2020, 10:34 AM
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arche3 arche3 is online now
Join Date: Jan 2001
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Posts: 1,110
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

Use only avid gear for protocols rig. Treat as tape machine. Buy only analog outboard gear to satisfy gearlust to post on gearsluts. The boutique ad/da gear are not nearly as slutty as couple LA2As. Or a massive passive. Or rack of 1073.... you get my drift.

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Old 08-18-2021, 12:05 PM
gandlz gandlz is offline
Join Date: Mar 2011
Location: Austria
Posts: 63
Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

After a few more mails I got this answer from Avid support:

"We have created the feature request ARSAT-3006 ...."

Is there a way to look at the progress of this feature request somewhere?
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Old 08-19-2021, 06:32 PM
albee1952 albee1952 is offline
Join Date: May 2004
Location: Norwich, CT
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Default Re: Compensate Input/Output Delay with external converters – not H/W Insert delay!

Just my thoughts as a long-time pro engineer:
1-fixing this is not very likely and I'm not convinced its an issue.
2-its very common for different brands of converter to have different amounts of latency.
3-its something to be aware of so you don't route certain combinations of inputs thru different converters, such as your left and right overhead mics, or any 2 inputs from a stereo source.
4-with the difference you are talking about, if you adhere to my #3, you will likely never hear any issue. I never did with my drum mics going thru a Midas XL48 coming in via ADAT and my overheads coming in from a Focusrite ISA-428 on analog inputs of an HD IO(its about the same as moving the overhead mics a few inches closer or further)
5-(again, my opinion); I believe you are over-thinking it
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