Can someone help me understand this behavior in regards too latency?

[skylar_battles]

Most of the time I am able to monitor through Pro Tools at a buffer size of 32. During the process of building out a song, of course plugins and routing are implemented.

What I don't understand is that after a certain point, if I make an audio track and attempt to monitor through it with no plugins and routing at all (audio straight to the monitors) there is problematic latency for recording a performance. I've tried various buffer sizes and changing the playback engine back and forth with no improvement. In the mix window, the track will report no delay compensation whatsoever, so why is there latency then? I can't imagine that at some point in building out a song, monitoring in Pro Tools is no longer possible?

I'll note that when I've had this before, just importing session data from a session with this latency problem seemed to mess everything up in the new session. I don't understand why and it is very problematic.

[Sardi]

Originally Posted by skylar_battles

During the process of building out a song, of course plugins and routing are implemented.

This is why.

If you’re adding plugins that incur latency, this will then be heard in your monitoring.

There will be no delay compensation for any latency inducing plugins inserted on your master channel, so that is the first place to look as a lot of people will start to add look ahead limiters etc. that can add a LOT of delay, particular when oversampling options are turned on.


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[skylar_battles]

If the track I'm monitoring through has no plugins or routing at all, then why would their be latency? I may be missing a fundamental piece. Even if I bypass my limiter on the master, it makes no difference.

[Darryl Ramm]

Bypassing a plugin does *not* remove it's latency. You have to remove or disable a plugin to remove it's latency. Very good reasons for this behavior... you can bypass a plugin on the fly to compare behavior.

And track is just a track, it's not the whole picture of signal flow. Make sure you are looking at all sends, bussing and master fader that is downstream from the track.

What *exact* latency delay are you getting that you don't expect. Setup a test and measure that, (e.g. with a click signal, recording back the monitored sound into a track with the live input sound sound, obviously mute that track to avoid feedback) the size of the latency can give a clue to the cause. hopefully measure within one sample accuracy.

You really should go though the exercise of working this out yourself, just getting comfortable things work exactly as expected. Start with a totally empty session. Add plugins to an audio track with say a mic you can click into. See if the latency reported for the plugin agrees with what is expected from the plugin documentation (or use Eventide Precision Time align that fakes out a few thousand samples of delay to the DAW to do it's thing... just a convenient no-op plugin with significant latency).

Add plugins to the master fader, what happens now? Again master fader plugins are not compensated/can't be... you can't time-travel back in time and there is nothing to compensate for so hear their full delay while monitoring. But any "things out of time" are... so all the components feeding the output/master fader line up is handled by ADC.

Presumably you are running Pro Tools native. TDM/HDX plugins can have latency as well, and these systems will also have additional latencies when transitioning between the DSP and native domain, and HDX plugins sure can have latencies as well.

Make sure ignore errors is not enabled, that can introduce small errors in latency and ADC.

Hardware inserts will add latency and that should be handled by ADC.

There are a few known bugs, including one with having sends enabled during LLM and using LLM that can introduce spurious latencies of exactly 2048 or 4096 samples depending on sample rate. Including in a hardware insert that follows a software plugin. It should be very obvious when this happens. Hybrid engine, including with Carbon, seems to have it's own ADC/latency issues. But many actual issues are typically user confusion with Pro Tools working as expected.

[skylar_battles]

"What sends, bussing and master fader is downstream from the track?" Not sure if this is what you mean, but in this case the track will being going straight to the monitors and will still have latency. I've tried to troubleshoot on empty sessions, but I never have problems until It's on an actual session, but I suppose more trial and error is needed. Are you alluding to that when the Master fader has inserts on it, that will always add latency? In my testing, bypassing all plugins on the master hasn't helped. I'm using Rosetta on a Silicon computer without any Avid hardware or any hardware inserts. I have ignore errors unchecked for the main playback engine as is the default, but it's still checked for AUX i/o even though I'm not using it, also as a default setting. Should I turn that off as well? I wouldn't think it could help.

[Darryl Ramm]

Again bypassing a plugin does *not* remove it's latency. You might have missed that on first read as I was editing the post.

You have input you are motioning on a track, but that signal can go many many places... sends, aux tracks feeding places, an I/O output (which is really a bus not a physical output) and to a output from that bus through a master fader to the physical I/O. So in the simplest setup you have one track and one master fader... but in real sessions you likely have much more complex routing for the monitoring signal. You can add monitoring latency anywhere withing this flow with plugins which have latency, since there is no such thing as time travel ADC can't correct latency when monitoring.

You need to follow that signal flow in your head, or maybe try to sketch it out it down on paper. Plugins on the master fader are classics for adding monitoring latency as folks are used to putting high latency plugins there. And be careful with hidden tracks that may still be active.

It is almost certainly something you are doing so you have to work through finding that. Try whatever you think will be easiest. Starting with an empty session or take an existing session, and do a save copy in then (being sure) work in that new copy session, and start doing surgery on that to delete stuff until you find what is causing the problem. Like make big changes to start with, hack away at many tracks etc. making them hidden/disabled (or delete them) that you think are not in the monitoring signal flow and then focus on finding the problem in the few tracks that you think are. It's a common mistake when trying to troubleshoot stuff like this to make small timid changes, you might end up being there forever. Make big bold changes and be willing to start over with another save copy in session if needed.

Or if you are really stuck, consider hiring a consultant to help you. Folks who really understand Pro Tools latency and ADC should be able to help you out pretty fast.

[Sardi]

Originally Posted by skylar_battles

Are you alluding to that when the Master fader has inserts on it, that will always add latency? In my testing, bypassing all plugins on the master hasn't helped.

Only if the plugins on your master fader induce latency. Not all plugins do.

Darryl has been pretty clear about it but hopefully the GIF I created can explain what we're trying to convey in a simple and elegant manner. (Picture paints a thousand words etc.)



When the insert slot goes blue, I've bypassed the plugin. Notice the latency remains (number at the bottom displaying delay in samples). When the insert slot is greyed out, the plugin is inactive. The delay now changes to zero.

In this example, my limiter is adding 3142 samples of delay. That is a lot but yours could be even larger. This will be adding a lot of delay in your monitoring chain.

Make sense?

[Darryl Ramm]

Now that's a neat, cute animation.

[albee1952]

Great info already. Here's a little more to help fry your brain. Here are some ways that latency creeps in:
1-Playback buffer setting. Lower numbers=lower latency, but put more strain on the computer. There is always some amount of latency and you need to decide how much you can accept while recording. You mention you use the 32 setting(as short as it gets) and that's great that your computer handles the load. For me, tracking full bands of 24-32 recording tracks and maybe another dozen(AUX tracks with FX), the 64 setting worked fine.
2-Plugins. As said, bypass does not alter the latency. Make a plugin inactive and that DOES solve latency for that plugin. To get a grip on this, you need to be able to see the Delay Compensation, so check that option under the View menu>Mix window(if you can't see the numbers, you can't identify where the problem lies)
3-How are you monitoring while track? If you listen to the main mix(as many do), plugins on the master track can cause no latency, or several thousand samples of latency(which you will hear if you try to record anything). If you monitor a separate mix derived from sends feeding a separate set of outputs, then whatever latency is caused by the master track will not(should not) affect the other outputs(my setup gave 6 stereo headphone mixes via sends on every track).
4-There is a known bug where a "homeless" send will cause almost 2000 samples of latency if the track is put into record. What I mean by "homeless" is, a send that goes nowhere. Example: you add a send feeding an AUX track with a reverb plugin, then you change your mind and delete the AUX track but leave the send in place.
5-Last thing to remember is; Delay Compensation works by making everything LATER to match the track with the most latency

[skylar_battles]

Sardi, thanks for your gif and explanation. I appreciate you demonstrating the difference in bypassing a plugin compared to making it inactive in regards to delay compensation. Perhaps when I thought bypassing my Pro-L 2 would help in the past, I most definitely should have been making it inactive for the reason you demonstrated.

Thanks for the info as well Albee. I am usually monitoring out of the master. I’d prefer to set the output of my vocal track, for example, to the vocal AUX (submix) but I’ve been told doing this while tracking will cause more latency. Have you found this to be the case? The homeless send thing very well could have happened in some of my sessions causing unpredictable behavior. That’s quite a bug though so I appreciate you mentioning it! Hopefully Avid can address that soon.