FabFilter User Forum

Pro Q3 CPU Spike Issues

Hi FabFilter!

We're currently running a single protools session for a film mix and we have ProQ-3 running on about 320 tracks. (Auxes and audio tracks)

We stumbled across an interesting side effect of using natural phase vs zero latency vs linear phase modes:

We will often group large amounts of these tracks and change their presets at once in automation preview mode, then write that to a selection in the tracks.

What we noticed is that when clicking around (i.e. when moving the playback head from one spot to another thereby triggering protools to read automation on the tracks), if a lot of ProQs have to switch presets at the same time there can be a very nasty 'CPU spike' (by looking at the system usage window in PT). What's more important is sometimes this spike is enough to freeze protools entirely, or cause playback issues and force us to restart protools.

We then started to mess with the phase modes and learned the following:

Zero Latency mode: Cpu spikes to about 50%
Linear Phase Mode: Cpu spikes to about 60%
Natural Phase Mode: Cpu spikes to 100% and cannot recover always

All this to say, it seems that Natural Phase mode uses up too much cpu to use reliably?

I'd be happy to provide a PT session so you can see for yourself.

Thank you!

Luciano Vignola — Jul 3, 2019

Hi Luciano,

We don't recommend using the processing mode during audio processing, since changing it reallocates memory internally and that can cause an audio dropout -- especially when many instances at the same time are doing this. For this reason, the processing mode parameter is not automatable anymore in the latest 3.11 version. Which version are you using?

I wouldn't expect Natural Phase mode to use more CPU than Linear Phase mode.


Frederik (FabFilter) — Jul 3, 2019

Sorry, to be clear, we're not automating the phase modes. The only thing we're automating is the preset at the top of the plugin (for example from "Flat 5 Bands" to "Flat 7 Bands"). We get the CPU error when that happens.

This error occurred on the latest version (3.11).

Luciano Vignola — Jul 3, 2019

Additionally, I'd be happy to post screenshots of this in action, if it helps you. Or we can provide you with a session. Whatever you need!

Luciano Vignola — Jul 3, 2019

Hi Luciano,

Well, the end result is the same... We just didn't design the processing mode switch to be a seamless real-time operation. Our idea is that you pick the processing mode beforehand and keep it the same during the entire session.


Frederik (FabFilter) — Jul 4, 2019

Instead of automating the switching of presets , I would put two instances of q3 on the same track, assign each instance the desired preset, and automate disabling one we while the other is enabled and vice versa.

Forrest — Sep 22, 2019

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