Utilizing Automatic Delay Compensation (ADC)

When you add a real-time plug-in or hardware insert to a track, it takes Pro Tools a little bit of time to process the signal. That little bit of time can cause latency or delay when playing back and recording tracks in Pro Tools. Automatic Delay Compensation or ADC, helps to manage the delays created from plug-ins and hardware inserts, and keeps all the tracks in the session time aligned. How does it work? Pro Tools adds the exact amount of delay necessary to each track, so that they all have the same amount of delay, thus keeping them all time-aligned.

We can adjust the delay compensation within the playback engine, if we go to Setup > Playback Engine. We can see right here Delay Compensation Engine. We can choose from four different values. The Short ADC value uses less processing power than longer ADC values, and should be find for any session that only has a few plug-ins on it and that don't induce much delay. Note that the number of samples per channel of delay shown here depends on the session's sample rate.

At higher sampling rates, the number of samples of delay will be larger. But the same amount of delay compensation from the time perspective will be applied regardless of the sampling rate. For instance, on the short setting shown here, there are 1023 samples of delay. At a sampling rate of 44.1 kHz, which is what we have for our session. If we create a session with the sampling rate that's double that, at 88.2 kHz, the Short ADC setting will be 2047 samples.

Double the number of samples, but equal to the same length of time, because the sampling rate is also doubled. The Long ADC value allocates a larger amount of resources for delay compensation. You should use this in sessions where there are a lot of plug-ins causing a large amount of delay. The Maximum setting should be used when the long setting just isn't long enough. Note that Pro Tools HD systems do not have this setting due to limitations with the TDM hardware. When you activate Delay Compensation, Pro Tools needs to reset itself and will save and close your session.

Let's check it out, and choose the Maximum value, and we get this dialog, Selecting this playback engine will automatically save and close your session. The session will be reopened when you are done changing settings. Are you sure you want to proceed? Choose Yes, and if we want to change anything in here, we can, but we're happy with it, so I want to click OK, and Pro Tools will reopen. And now we can see the Delay Compensation is on, we can see it right here. With it on, now we can go to the Options menu, and choose whether we want to keep it on or turn it off.

So if I check this, now I have actually turned off the Delay Compensation. We don't see it here anymore. I can go back to the Options menu, click Delay Compensation, and it will turn it back on. Now you don't need to activate Delay Compensation when you're recording your first tracks in a session. However, once your session starts to become a little more complicated, when you've got a bunch of plug-ins, effects loops, virtual instruments, using ADC will become a necessity to keep all of your tracks time-aligned.

I recommend enabling Automatic Delay Compensation during most playback and mixing sessions, and also during many recording situations. I'll discuss much more about ADC in the recording and mixing chapters in this course.