How to Compensate for Interface Latency in Pro Tools?

[Greybelly]

I can not find a way to compensate for my audio interface latency.
Here is how to reproduce the issue.
1. Record a click track to track 1 in Pro Tools.
2. Play it back out to a speaker.
3. Record the sound of the click using a microphone onto track 2 in Pro Tools.
4. The microphone is connected to an audio interface that converts the signal from analogue to digital.
5. The digital signal goes out of the audio interface and into a computer running Pro Tools.
6. Now compare the wave forms of track 1 and track 2.
7. The latency can be measured by comparing matching clicks and noting the different leading edge start points.
That latency needs to be compensated for. Track 2 needs to be automatically shifted forward in time by the amount of latency measured. Any and all tracks that are recording from that audio interface need this adjustment. An expanded description of the problem can be found at this link. https://wiki.cockos.com/wiki/index.p...erface_Latency It seems the REAPER DAW has a preference setting to accommodate for this issue.
A few places in the Pro_Tools_Reference_Guide_2022.6.pdf hint that this can not be done unless you have AVID hardware, like on page 1119.
“Pro Tools Ultimate accounts for converter delays
when using Automatic Delay Compensation.
However, when using non-HD hardware,
System Delay only displays internal delay and
does not take into account any latency incurred
by the analog-to-digital (ADC) or digital-
to-analog (DAC) converters in your audio
interface.”
A similar problem can occur with hardware insert delays. Pro Tools seems to have that covered though (see “Setting a Hardware Insert Delay Offset” on page 1124).

Delay Compensation as mentioned on page 1118 is only for internal delay compensation and hardware insert delays. No mention of audio interface delays here.


Manually setting a Delay Compensation on every track that needs it is a terrible work around.


Maybe the audio interface driver is supposed to report the interface delay to Pro Tools?
What if the audio interface driver does not report the interface delay to Pro Tools?
What if the audio interface driver reports the interface delay incorrectly to Pro Tools?
What if Pro Tools takes no notice of such things?

Any help shedding some light on this topic would be appreciated.

[lesbrunn]

Originally Posted by Greybelly

I can not find a way to compensate for my audio interface latency.
Here is how to reproduce the issue.
1. Record a click track to track 1 in Pro Tools.
2. Play it back out to a speaker.
3. Record the sound of the click using a microphone onto track 2 in Pro Tools.
4. The microphone is connected to an audio interface that converts the signal from analogue to digital.
5. The digital signal goes out of the audio interface and into a computer running Pro Tools.
6. Now compare the wave forms of track 1 and track 2.
7. The latency can be measured by comparing matching clicks and noting the different leading edge start points.
That latency needs to be compensated for. Track 2 needs to be automatically shifted forward in time by the amount of latency measured. Any and all tracks that are recording from that audio interface need this adjustment. An expanded description of the problem can be found at this link. https://wiki.cockos.com/wiki/index.p...erface_Latency It seems the REAPER DAW has a preference setting to accommodate for this issue.
A few places in the Pro_Tools_Reference_Guide_2022.6.pdf hint that this can not be done unless you have AVID hardware, like on page 1119.
“Pro Tools Ultimate accounts for converter delays
when using Automatic Delay Compensation.
However, when using non-HD hardware,
System Delay only displays internal delay and
does not take into account any latency incurred
by the analog-to-digital (ADC) or digital-
to-analog (DAC) converters in your audio
interface.”
A similar problem can occur with hardware insert delays. Pro Tools seems to have that covered though (see “Setting a Hardware Insert Delay Offset” on page 1124).

Delay Compensation as mentioned on page 1118 is only for internal delay compensation and hardware insert delays. No mention of audio interface delays here.


Manually setting a Delay Compensation on every track that needs it is a terrible work around.


Maybe the audio interface driver is supposed to report the interface delay to Pro Tools?
What if the audio interface driver does not report the interface delay to Pro Tools?
What if the audio interface driver reports the interface delay incorrectly to Pro Tools?
What if Pro Tools takes no notice of such things?

Any help shedding some light on this topic would be appreciated.

What buffer size are you using?

[climber]

Originally Posted by Greybelly

Any help shedding some light on this topic would be appreciated.

and you've provided absolutely no info on your setup. not even the interface name... [sigh]

[Ben Jenssen]

Let's have this straight from the start; PT automatically compensates for the latency induced by the playback buffer, so it doesn't matter if it's 1024 samples, PT will adjust the recorded audio 1024 back. You will hear the audio latency as you record, of course, but the audio will be right on spot when you play it back. It does not compensate for interface latency.

[JFreak]

Originally Posted by Robruce

That's a great feature in Reaper. There's always going to be some amount of A/D delay, so why not provide a track offset option?

thereis INPUT offset available, mthat is even better. though it could be sample based instead of ms

[Darryl Ramm]

Originally Posted by Robruce

Searching "Input Offset" in the Ref manual (2022.4) shows no results. I see track offset for dealing with plug latency, MIDI offset, SMPTE offset, hardware insert delay...

Is it called something different? I obviously need to read up on it.

Yep very confusing. I suspect Janne meant "Insert delay" not "input delay" since he mentioned it being in ms (which insert delay is... way way past time that Avid had fixed that stupidity and made it samples or given a choice).

[albee1952]

Just my 2 cents, routing as the OP describes, I would expect exactly what they are getting, especially if there are any plugins in play that have latency(doubly so if they are on the Master Track). I would never expect sample-accurate recording with speaker and mic because there will always be at least a slight delay between the speaker and the mic(subject to actual distance)

For myself, recording with a low buffer(64) and wise plugin choices has made latency a complete non-issue here. Regarding hardware inserts, a few things matter; 1-what hardware and interface? 2-with "budget" hardware, I say save the hassle and stick with plugins(because they will match or beat the results, with zero hassle). I love hardware as much as anyone, but there are plenty of reasons to skip this, unless your hardware is exceptional(got a real Fairchild? Absolutely find a way to use it!). My external hardware use is during tracking, which gives me all the flavor, with none of the headache. again, just my 2 cents

[Darryl Ramm]

I can not find a way to compensate for my audio interface latency.
Here is how to reproduce the issue.
1. Record a click track to track 1 in Pro Tools.
2. Play it back out to a speaker.
3. Record the sound of the click using a microphone onto track 2 in Pro Tools.
4. The microphone is connected to an audio interface that converts the signal from analogue to digital.
5. The digital signal goes out of the audio interface and into a computer running Pro Tools.
6. Now compare the wave forms of track 1 and track 2.
7. The latency can be measured by comparing matching clicks and noting the different leading edge start points.
...

Oh joy, latency. Always good for some confusion, misinformation, and unfortunately lots of online forum masturbation.

It's great you are trying to understand stuff but lets step back and ask what actual recording problem are you trying to solve? I'm assuming this synthetic experiment is not your actual problem.

Pro Tools just deals with I/O and interface latency automatically, you normally don't need to worry about it. If it did not just work all hell would break loose. Some of the implications of the Pro Tools doc about not correcting conversion latency are incorrect. Pro Tools very clearly uses the latency data exposed in interface device drivers. If it did not do that all hell would break loose for many users.

And if an interface driver advertised wrong latency information, which is used by all DAWs, all hell would break loose there as well. I will not be surprised if there are some very rare are mistakes out there, especially amongst small boutique interface vendors with small engineering teams. But still very very rare. But there are cases of problems/limitations of how this works (interfaces effectively provide a single latency spec to the DAW for the whole interface, even if not all ports have that same latency) that do trip up users.

In your experiment there is a very real latency (~1ms per foot) caused by sound propagation delay from the speaker to the microphone. There is nothing "automatic" that can/should be done for that. And this is an unusual setup in an audio recording, Pro Tools can't tell what you are doing, maybe you want that real world delay in what you are recording. Who knows. If this happens and you need to correct it manually you can just slide around content in a track manually.

And a trivial example to show basic stuff just works.... I'm using an RME Fireface UFX+ interface, here running at 48 kHz. See the screenshot of a trivial test using a standard click track. https://drive.google.com/file/d/1SMY...ew?usp=sharing

I'm using multi-output on the click track to send the click concurrently to physical analog output 3, MADI output 1, and to a Pro Tools internal bus. Analog output 3 is physically connected back to input 3 and the MADI fiber optic cable is looped back on itself so MADI output 1 goes back to MADI input 1. There are three audio tracks recording analog input 3, MADI input 3, and the bus the click is going to. I used clip gain to reduce the bus track waveform so they are all the same rough height.

Look at the results. The click waveform on analog input 3 lines up exactly with the waveform on the track recording the bus. That shows that Pro Tools is correcting for converter and IO buffer latency for the interface. Ah and what about the MADI loopback... the track recording that has a signal set back 20 samples before the others... that is because the actual RTL latency of the MADI loopback is 20 samples less that the RTL of the analog loopback, and the interface just report the analog port latencies so here Pro Tools is applying the converter etc. latency to the MADI and because that's too much compensation it's moved back in time more than likely wanted. This is easy to correct for adding a plugin like Time Adjuster or Eventide Precision Time Align. And this is *expected* behavior once you understand what is going on.

All this alignment of interface input/output happens without "latency compensation" being enabled... that's for plugin latency processing and hardware inserts latency (and if latency comp is enabled Pro Tools *does* correct for the converter latency on the input and output converter of a hardware insert).

In practice Core Audio and ASIO drivers do not provide different latency data for different IO ports or groups of ports. CoreAudio at least (not sure about ASIO) actually could advertise that latency difference using different per-stream latency, at least here since MADI and Analog signals on the UFX+ are already separated into different streams, but that's not how DAWs are willing to interpret latencies and it would likely break lots of things.

Some of the Pro Tools reference guide seems to needs improvement around discussing latency, I also thought Avid was saying converter latency was not compensated for in non-DigiLink systems when I first read that documentation. But it's clearly is being corrected for when you actually measure stuff. I suspect what Avid might mean is that Pro Tools HD/Ultimate with DigiLink correctly compensates for this difference between different port latencies regardless of if are analog or AES/EBU, ADAT, MADI etc.. It might do this by simply padding more latency on the digital I/O. I'd love to measure what they are doing (I don't have a DigiLink rig).

[lesbrunn]

Originally Posted by albee1952

Just my 2 cents, routing as the OP describes, I would expect exactly what they are getting, especially if there are any plugins in play that have latency(doubly so if they are on the Master Track). I would never expect sample-accurate recording with speaker and mic because there will always be at least a slight delay between the speaker and the mic(subject to actual distance)

For myself, recording with a low buffer(64) and wise plugin choices has made latency a complete non-issue here. Regarding hardware inserts, a few things matter; 1-what hardware and interface? 2-with "budget" hardware, I say save the hassle and stick with plugins(because they will match or beat the results, with zero hassle). I love hardware as much as anyone, but there are plenty of reasons to skip this, unless your hardware is exceptional(got a real Fairchild? Absolutely find a way to use it!). My external hardware use is during tracking, which gives me all the flavor, with none of the headache. again, just my 2 cents

I share that sentiment exactly. With the exception of a rare anomaly that I recently experienced, 64 is the way I track without any latency. Anything else can come after I've done that.

[EGS]

+1 for tracking at buffer 64