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.


Examples:
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.


Conclusion:
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,
Gandlz

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.

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…
https://protools.ideascale.com/a/dtd...ion/17518-3779

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.

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.

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

Not exactly a new issue.
https://www.gearslutz.com/board/show...4&postcount=22

The suggestion on Ideascale never got much traction.
https://protools.ideascale.com/a/dtd...ion/17518-3779

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.

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.



Sent from my SM-G986U using Tapatalk

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?

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:o

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

I am unclear as to the bottom line about whether there is a way to compensate for input delay after recording if I am not running and Avid interface.

I have PT Studio 2022.7.0 with a MOTU 896mk3 interface. If I send a click out of the 896 and patch a cable directly back into another input and record, the delay is 7mS. That means any overdub played while monitoring the exiting track is 7mS late. (It seems unlikely that that much delay would be caused by a DA/AD conversion, so perhaps there is some input latency associated with PT itself?)

In any case, I cannot find "Compensation for Input Delays After Record Pass" in any of my menus. I have tried setting the delay times in the H/W Insert Delay tab in I/O Setup and it has no effect.

Is there any way to preserve the temporal integrity of the signals coming in relative to what is being played back other than manually nudging every time?

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

0.68ms not acceptable? Do you realise you need to be speaking closer than 20cm (8inch) to a person to get lower latency? How come people on stage are able to perform?

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

I think the 0.68ms comment is related to my initial post.

Take one of your good recorded songs (progressive rock or other heavy rhythmic genres) and nudge your perfectly recorded vocals 0.68ms to the right.

How do your vocals "feel" now?

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

That would be 30 samples and even early reflections of reverb have not kicked in that fast. Really don't try to find a problem where there is none. But if it really bothers you, you know that you need to nudge that 30 samples every time.

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

When my brain starts to notice events on the 30 samples order of time scale, I take that as a cue I forgot my meds that morning or I should go to sleep or consume less coffee. Literally, I have schizophrenia and VERY odd audio time perception sometimes).

The perception of time is relative, and if you notice a sound maybe no one else does or even can. Literally. Maybe the scope cannot even tell. Base level beta wave consciousness is on the order of 12-38 Hz. I think on a brain processing level that's like a sample rate, and introspection, memory, muscle memory, and musical groove anticipation directly inform the nature of the next moment's "drum hit" (to keep it tribal, where our consciousness evolved). The anticipation of a 30 sample blip might become like the most significant thing if you sample RIGHT at the specific moment and get an outlier (every time). (On an EQ spectrum curve you see .._/-- or .__/-- so almost the same, but try again, it changed, so it seems like a PHASE ISSUE but is something else.... less strange than weird you know)

Doing weird things to phase as Albee mentioned to tightly correlated signals like stereo overheads, sure something might come up and be slightly audible. But overall, telling people it really really should be a super intense focus would be what people are pulling back on in the thread. Mostly, no one hears a difference, where there is in those specific outlier situations, being able to measure and manually nudge a track is a great enough and not too convoluted of a process.

Perhaps the computation necessary for auto magically timing everything would limit the sample rates so much we'd go from 192kHz/32bit to 12kHz/4bit recording again, with today's computers I mean.

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

I'm not sure what exactly how you are getting this. Pro Tools actually should be compensating for I/O latency. And it does when I test it.

With my RME Fireface UFX+. A click track, is multi-output: to line Output 3 which is electrically connected to line Input 3, and the click track is also output to bus 2. Track Audio 1 records Input 3, and track Audio 2 records Bus 2. They align within a sample. 96 kHz session but that won't matter. 256 sample IO buffer, but that IO Buffer size is compensated for automatically, along with the conversion latency. Attached screenshot shows the sample accurate alignment. Delay comp should not need to be enabled (it does if you were using HW inserts).

Are you using more complex routing? via sends? Start with a stupid simple test session, not using aggregate I/O. No software plugins or hardware inserts. Make sure you do not have MOTU DSP effects (do any of them have any latency, or signal loops in the MOTU hardware monitoring?), disable all that. Try to reproduce the problem you are seeing with the most trivial test session you can and share it online.

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

Thanks for the suggestion, Darryl. I created a minimal session and measure the time delay as 2 ms. Here was my process:

• Create minimal Pro Tools session with no plug-ins except a single instrument to generate a click
• Play click track out through hardware output 8 of MOTU 896mk3
• Cable output 8 to input 8
• Record input to an audio track in Pro Tools
• Compare original click and recorded sound
• Recorded sound is 2 ms late

Attached screen shot shows:

• Original click instrument track
• Committed version of same
• Internal bounce of click (send to internal PT bus and use same as input to a new audio track -- timing is sample accurate with committed track)
• Analog signal recorded as noted above - 2ms late

That seems like way more than it should take to go DA/AD, but it is within an acceptable range and if the delays were consistent, I would go on my merry way. However, my problem is that I am experiencing different delays at different times. With the same session (all the same tracks, I/O, plug-ins, etc.) I have experienced delays between 2ms and 45 ms. Most of the time, it's 2ms, but there are times when I record an overdub and it is obviously out of time. In those cases, when I immediately run a test per the above, the delay is closer to 45ms. Since the results with the exact same session are not consistent, it is very difficult to figure out the cause. The fact that I measure 2ms with my minimal session may have nothing to do with it being minimal since most of the time more complex sessions perform just as well. It is possible that if I spent long enough in the test session recording and listening to clicks, it would eventually deviate as well, I just don't think my soul could endure that. :(

As all intermittent behaviors, this one is pretty difficult to troubleshoot so any further suggestions are truly appreciated.

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

Well, I have to correct my last post, as I was answering in a hurry and it's also some time ago I was in this topic. Actually, after posting I thought to myself, there is something wrong now in hearing 30samples delay on one track. I’m sorry for that.

So these 30samples or 0.68ms are what my clips where off in timeline after recording pass in my special scenario with mentioned converters.

The Problem in fact was that some were monitoring through external converter on ADAT and others from 192 I/O analog outputs. What Pro Tools compensates for those outputs is one story, the other one is, that these converters have different speeds, so people where hearing their mix at different times. They all felt groovy while playing but then listening to the take in control room, they were shocked about their performance first but soon was clear that there is some latency issue.
The different converters for input signals were also supporting this timing issue.

The only thing I can tell for sure is, that buying one more 192 I/O and changing everything to their analog I/Os fixed everything for me.

Maybe it would not be a problem to keep some ADAT or AES Inputs and accept them to be about 16samples late. But I really recommend everyone in studio to listen through the same Output converter.

Kind regards,
Gandlz

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

Nothing beats good testing. Darryl owns this line, by the way.

Now that you know two things:
- this does not affect groove, recording is omkay
- this makes the recorded track 30 samples late

... all you need to do is nudge back 30 samples after recording.

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

30 samples can't possibly have an effect on perceived groove.

Right? That's got to be within the brain's reaction time and margin of error. An Aviom would add more latency and I don't see complaints with those.

Analogue outputs and digital outputs going to converters have always exhibited different latencies. Nothing new there. I struggle to sense the problem.

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

I missed your reply before.

This absolutely does not happen for me. I get sample accurate behavior (most 6 versions of Pro Tools, most recent three major releases of macOS, three different RME interfaces). But you are skipping over some stuff about how exactly you do things, like what exact track was committed and why did you do this? Is that related to a problem you are trying to solve? If not can we focus on what is the absolute minimum test that shows the problem. Like if you just record click bussed to an audio track and click out and back into the interface

More info would probably help.

Confirm you are not using aggregate I/O

Does enabling or disabling latency compensation make any difference here?

What are your main outputs that you are monitoring though while doing all this? I want to make sure there is a separate main audio monitoring path, and it does not involve output 3.

Make sure you are not in LLM mode, or if you have been test again without. There is at least one known bug with LLM and some hardware insert and plugin combinations badly borking delay hardware insert compensation, maybe there are other problems with LLM.

Do you have another interface to test with?

Can you share a copy of your session.

You say the latency varies, I think you have to keep trying to work out what you change to get it to vary. Any chance it's sample rate? Or wether LLM is enabled? Or...

If you are willing I'll can also get you to run a test on the interface RTL and some other reported latency independent of Pro Tools. We can take that offline.