Latency and Delay Compensation in REAPER

If you have been working with audio for a while, then it’s inevitable that you’ve dealt with latency. The phenomenon is embedded in the functioning of digital audio systems and can’t be avoided. Instead, the usual approach is to minimize it and compensate for it. REAPER as most DAWs out there, has a few Delay compensation systems that I’ll be exploring in this article.

realinsert REAPER

Most DAWs have at least a few systems to compensate for latency whereever it’s possible. REAPER, in my opinion, is one of the best in this regard. However, these Delay compensation systems are not perfect, and you may find yourself having to adjust any one of them at any given time. This is why it’s important to learn about them and master different ways to deal with them. Let’s begin by first exploring the concept.

What is Delay Compensation?

Delay compensation in REAPER is applied when a signal has to go through a process that returns the signal delayed or “late”, therefore, misaligning the track from the rest of the tracks in the project. At a minimum, this can cause phase issues, and at its worst it can make the track sound completely out of whack compared to the rest of the song.

delay compensation REAPER

In essence, all systems do the same thing, and it’s pre-adjusting the delay of a track so when it goes through the process, the signal comes back aligned to where it should be. It can be done “Inside the box” or “Outside the box” with some conditions, let’s explore how each of them work and when it may be necessary to adjust them manually.

Delay Compensation Systems

Plug-in Pre-Delay Compensation(PDC)

The easiest Delay compensation system to understand in REAPER is the Pre-Delay Compensation(PDC). You apply this to FX Chains when a Plug-in reports delay in your audio. This means that the higher the reported latency (of the plug-in), the harder it will be for you to live monitor yourself through it. Check this article if you want to know more about how this system affects latency while live monitoring.

pre delay compensation reaper

This behavior is usual in plug-ins such as pitch shifters, automatic pitch correction, de-noisers, linear phase EQs and most plug-ins that use heavy internal oversampling. You can spot it by checking the PDC numbers in your track FX chain or in REAPER’s Performance meter.

plugin delay spls reaper

It’s rare that you would have to modify the internal PDC manually unless there’s a plug-in that doesn’t properly report the delay that it introduces to the signal. However, if you have to, you can disable Pre-Delay compensation in the FX Chain.

FX ignore plugin delay reaper

Adjust manually using a time alignment plug-in or with the Media playback offset option that is available in each track routing window.

media playback offset reaper

Hardware Inserts Additional Delay Compensation

Hybrid mixing is a commonly used technique that involves using hardware processing units while mixing. It can introduce latency since you’re going through the interface converters in and out.

hardware inserts reaper

For this purpose, REAPER has an integrated plug-in called ReaInsert. It uses your hardware outputs, inputs and your interface’s reported Round-trip latency to calculate how much to compensate for the time it takes your audio to go through the whole Out of the box signal chain.

ReaInsert REAPER

If for some reason your Audio device reported latency, used by REAPER for Automatic device latency adjustment, is not working properly (and in my experience it often does), you can use the Ping detect option.

additional delay compensation reaper

You can also disable the Automatic device latency adjustment altogether and adjust the Additional latency compensation manually instead.

Audio Device Reported Latency

If you check out my article on Sample Rate and Buffer size settings, I’ve gone in depth about audio devices and the latency they impose. The thing is that oftentimes, Audio devices report their latency slightly wrong, causing elements in your recording to sound a little bit later or earlier than what you actually played.

audio device reported latency reaper

REAPER has an option in Preferences > Audio > Recording to manually modify the Input and Output latency. It can be modified in milliseconds, samples or both.

audio driver reported latency reaper

To test this, you can do a loopback by connecting one of your interface outputs to an input.

loopback audio interface

Then playpack your audio with a clear transient that will get recorded to a new track.

audio playback reaper

The difference between the two waveforms is the latency that your audio interface is not properly reporting.

audio interface latency flaw

If you want to know more and follow a video that explains it more in detail and step by step, check this official REAPER tutorial.

audio driver reported latency REAPER

Final words

Delay compensation is one of those things that isn’t flashy at all! It’s baked into everything you do inside a DAW. Take your time to know and experiment with it so you’re in total control of what you’re doing. It will save you more than a few headaches if you ever find something sounding weird for no apparent reason. I hope this article has been useful, feel free to check out more in the REAPER section. Happy mixing!

Jose M.
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