Reaper Script: Things out of sync? -Meet Noisebud Project Sync

This is 100% free for everyone.

This project started because of a mastering job that went slightly wrong.

I was mastering a new album for one of my favorite clients, someone I always really enjoy working with. It was a very good album and I really wanted to do it justice, so I spent a lot of time on it and was very happy with how it sounded.

I listened through the first renders as part of my normal QC, found a few small things I wanted to fix, went back into the project and made the changes. Then I rendered new files.

And this time I didn’t listen through all of them again before sending them.

A while later I got a message from the client listing roughly half of the songs. The vocals and rap were out of sync.

Not exactly the message you want to get after mastering an album.

For this particular project I had asked for stems, but not because I wanted to remix anything. Quite the opposite.

On some songs I thought the vocals sounded perfect and I didn’t want to touch them at all, but there were things I wanted to do to the music. On other songs the music was already where I wanted it, but I wanted to do something to the vocals.

Having stems meant I could process less, not more.

The problem is that my mastering template has become pretty complicated over the years. Audio gets sent left and right, forwards and backwards, through parallel buses and different processes to do all the little tricks we do in mastering.

That works very well until something somewhere reports its latency slightly wrong.

A plugin being off by a couple of samples is quite common and usually not the end of the world. But once you combine several of those plugins with complicated routing and parallel paths, those small errors can start adding up and spreading through the project.

That is what had happened here.

I had one, two, maybe three plugins in the project reporting slightly incorrect latency, and together with the routing in my template the vocals ended up around 150 ms out of sync on some songs.

I fixed most of the affected songs manually. I imported the original stereo mixes with the vocals intact, compared them against my stems and moved the vocal stems until everything lined up again.

But while doing that I started thinking:

Why am I doing this manually?

Surely I can measure the actual timing at the end of every signal path and correct it automatically.

So I built Noisebud Project Sync.

How it works

The idea is pretty simple.

You place the supplied sync signal at the same position on the tracks you want to line up and put a Project Sync Probe plugin at the end of each signal path.

The controller then measures when that signal actually reaches every Probe and shows the timing difference in samples.

Press CHECK SYNC, and Project Sync measures the real result of the complete signal path.

It doesn’t care what REAPER thinks the latency should be. It measures when the signal actually arrives.

If something arrives early, APPLY CORRECTION adds the required sample delay so all measured paths line up with the latest one.

The correction is deliberately not reported to REAPER as PDC. It is simply a real sample delay inside the Probe, so REAPER doesn’t get a chance to compensate for the correction again and move things out of sync.

There is also a BYPASS SYNC button, which temporarily removes all correction from every Probe.

This makes it very easy to A/B the project with and without the timing correction while listening.

The sync signal itself became a little more elaborate while I was building this.

It uses a coded noise marker followed by an irregular pattern of impulses. The Probe knows the timing pattern and uses it to identify the earliest valid arrival, which makes the measurement much more resistant to things like short slapback delays and Haas-style stereo widening.

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The workflow is simply:

CHECK SYNC → APPLY CORRECTION → listen and use BYPASS SYNC for comparison

This is mainly something I built because I needed it myself for stem mastering. But if you work with complex routing, parallel processing or latency-heavy plugins in REAPER, I suspect it could be useful there as well.

Download

Files are attached directly to this post as a zip arvhive:

Project Sync Controller
Project Sync Probe

30-second sync signals in:

44.1 kHz
48 kHz
88.2 kHz
96 kHz
176.4 kHz
192 kHz

The same files are used on macOS and Windows.

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https://www.patreon.com/Noisebud/posts/170543040

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