Track Input Monitor: Delay

[pasthq]

Hi there,



I want to have the Input Monitor Delay set automatically, so that it goes to a specific value when I activate it. Is it possible?


e.g. I have a Kick Drum recorded and want to overdub in sync but would have to put the Track Input Delay -760 for the to be recorded channel to be in sync. I would ideally want to not have to adjust this manually every time.

[Darryl Ramm]

Is this related to your other question today about hardware inserts?

Audio track input delays are automatically compensated for in Pro Tools, this happens all the time and does not need ADC to be enabled (HW insert do need ADC enabled to compensate for their input and output latency).

Make sure ignore errors is not checked.

What is the exact interface, what exact IO inputs on that interface, what signal flow, etc. is being used here.

[pasthq]

Originally Posted by Darryl Ramm

Is this related to your other question today about hardware inserts?

Audio track input delays are automatically compensated for in Pro Tools, this happens all the time and does not need ADC to be enabled (HW insert do need ADC enabled to compensate for their input and output latency).

Make sure ignore errors is not checked.

What is the exact interface, what exact IO inputs on that interface, what signal flow, etc. is being used here.

Thanks so much for your answer.


I am using a Focusrite Scarlett 18i20 and an Octopre and I basically just record AKAI sampler into ProTools using an external sequencer (Atari) and ProTools 12.



In Ableton usually I used to have to put manually the track delay according to the roundtirp latency of the sampler and thought I had to do the same in Protools. Ableton would actually then be able to have the input monitoring on grid with the actual recording. Somehow this is have to be done manually in PT with the +/- and "I" enabled.

[Darryl Ramm]

ADAT, well there is one problem...

Kinda ignoring the whole "overdub" part to start with...

Pro Tools will automatically correct for the input latency reported by the interface device driver. But...

Interfaces can/will have different input latencies for different IO, for example digital IO should usually have less latency than analog IO.

It is possible for interface drivers to report these different latencies (at least on Core Audio which I am familiar with the internals of, I am not familiar with ASIO), all DAWs I am aware of only pay attention to the latencies reported in the first IO stream on the interface... so typically the analog IO on most interfaces.

And in addition the case of an ADAT (or AES/EBU, or S/PDIF, or MADI, or...) convertor/preamp there is no way for the external box to communicate its additional conversion latency to the interface so the device driver could add that to the raw digital IO latency and then report that to the DAW. But even if it could the DAW is likely to ignore it anyhow.

That additional preamp/convertor box latency will typically be much less than a HW buffer size, maybe ~ten to tens of samples. But you already have a difference in the interface where its digital input ports will have less latency than its analog inputs. In your case the total input latency on the Octopre analog inputs could be less or more than the analog inputs on 18i20. But Pro Tools is going to universally apply a correction for the 18i20 analog inputs so the analog inputs on the 18i20 will be correct but the analog inputs on the Octopre may appear later or earlier in time.

This input correction is applied by Pro Tools all the time, it is independent of ADC. But you can correct it by measuring the latency difference between 18i20 analog inputs and the Octopre analog inputs and turning on ADC and applying the needed +/- correction to the tracks from the Octopre. But remember that ADC is disabled for track in input mode so you don't hear this correction when monitoring.

The easiest way to compare those two input latencies is to run one mic into a splitter cable and clap or click into the mic and measure the difference in time. Or you can split a click track output and route that out a pair of outputs on the 18i20 to analog inputs on the 18i20 and Octopre. These latency differences can/will change at different sample rates and H/W buffer sizes.

If you are measuring the difference between 18i20 and Octopre inputs as 760 samples you are likely doing something wrong, it should not be that large. But I have no idea exactly what you are doing when you get that measurement. And likely that includes some other latency from your sequencer/sampler.

Do the latency difference measurements starting with a new empty session with just two input tracks, absolutely no plugins on input tracks. Measure without ADC enabled, enable ADC and apply the correction you needed in the +/- field and then repeat the test and confirm the signals now align. With care you should be able to measure to one sample accuracy.

Make sure that ignore errors is *not checked* (and do not check it later as it has latency error inducing bugs).

Still having problems, post the measurements you get, describe how exactly you made them, the HW buffer size, sample rate etc. Ideally report several measurements at different sample rate and HW buffer size.

---

The higher level question is what are you really doing with overdubs and are you playing along in real time then there is an output latency and maybe latency of the sequencer/sampler as well involved here. None of that is really up to the DAW, but if you can measure a fixed latency you can also correct for that. And potentially you might be better off doing this with plugins/VIs?

But I would start by understanding the interface and ADAT box input latencies, getting them lined up and the working out what else is going on.

[BScout]

Originally Posted by pasthq

Hi there,



I want to have the Input Monitor Delay set automatically, so that it goes to a specific value when I activate it. Is it possible?


e.g. I have a Kick Drum recorded and want to overdub in sync but would have to put the Track Input Delay -760 for the to be recorded channel to be in sync. I would ideally want to not have to adjust this manually every time.

User delay comp at the bottom of mix channels happens after the record signal is put to disk. Not before. It's compensating -- it's not moving where the audio recorded to.

If you want to put the kick (for instance) on the grid with a delay, create an aux track, assign the input to be your hardware input for the kick mic, assign your output to another bus. Create a audio record track, assign the input to be the output bus you set up earlier. Put on the aux a delay plugin (Avid Time Adjuster is a good/free one that comes with Pro Tools) and adjust how much delay you want.

What happens then is:
kick mic > hardware input > aux track with delay plugin adjusted > record audio track

[pasthq]

Originally Posted by BScout

User delay comp at the bottom of mix channels happens after the record signal is put to disk. Not before. It's compensating -- it's not moving where the audio recorded to.

If you want to put the kick (for instance) on the grid with a delay, create an aux track, assign the input to be your hardware input for the kick mic, assign your output to another bus. Create a audio record track, assign the input to be the output bus you set up earlier. Put on the aux a delay plugin (Avid Time Adjuster is a good/free one that comes with Pro Tools) and adjust how much delay you want.

What happens then is:
kick mic > hardware input > aux track with delay plugin adjusted > record audio track

Thank you guys! That was really helpful. I will check everything