Pops from ADC question/issue

[Frank Kruse]

Hi,

today I had an issue where suddenly my work session would click and pop when playing low frequency content on one of my fx-tracks. First I had a glitch in a hidden automation lane in mind but there was nothing. The clicks where always in the same area but never in the exact same moment. So it could have been a drive issue. I copied everything to a new drive but the same thing happened.

When I moved the sound to a different location down the time-line the clicks where gone. Move it back to where I need it, clicks come back.

Then I tried to hit auto-suspend and voila! no clicking. So I thought I MUST be the automation. I checked all lanes on all busses that this sound went through till it reached the out but no spikes in any of the lanes. But still when I hit suspend no clicks.

Then about 2 minutes before I started to re-install the whole system I noticed that in the Mix-Window of PT the delay-compesation engine dynamically switches it’s shown values exactly when I hear these pops and clicks!!!

Till today I wasn't even aware of of this feature. I never thought the ADC would dynamically change it's values while you are playing. So learned something new there.

SO it turns out it’s actually a plugin in the session that changes it’s reported delay and then PT compensates the other tracks /busses. This leads to these clicks when playing low frequency content on a totally different track..

So I took the time to narrow down the offending plugin and landed on one of the FabFilter PRO-DS plugins on my dialogue-tracks. I noticed that there was an un-intentional automation that switched from wide-band to split-band and back which caused the ADC-engine to adjust all other tracks which then leads to the clicks. Note that the switch happens outside of any audio playing so on an empty section of that DX-track.

If it’s a feature it’s not a good one because even when there’s nothing playing through the plugin the ADC engine will still do the re-compensating. This is kind of a dangerous thing as it makes automation switching literally impossible as it might cause clicks on busses that have nothing to do with where the plugin actually is.

I must say that I had no idea to this day that this is the way ADC works. I always thought it's a static setting at least over the course of a play-pass. Is this a feature that I wasn't aware of all these years? Or is this something that can be fixed on the plugin manufacturer's side?

Thanks!

Frank.

[dieffe]

whoa! that's weird. didn't know that something like that could happen.
Maybe it's connected to the dynamics plugin processing? I'm sure some guy from Avid can tell us more of what's happening behind

[Frank Kruse]

Originally Posted by dieffe

whoa! that's weird. didn't know that something like that could happen.
Maybe it's connected to the dynamics plugin processing? I'm sure some guy from Avid can tell us more of what's happening behind

No, it happens regardless the dyn. plugin proc. setting.. All that does is "turn off" any plugins that do not currently have anything to process and then turn them back on if there's stuff to work on.

You can actually easily illustrate the issue on your system. Just put in a plugin that has latency relevant parameters like look ahead, FIR vs. normal EQ etc. then open the mixer window and watch the ADC values change when you switch the settings in the plugin while you play.

Frank.

[reichman]

Whoa. Avid shouldn't allow the automation of parameters that would impact the delay time that a 3rd-party plug-in reports to Pro Tools. I had no idea ADC could be updated during playback.

[Frank Kruse]

Originally Posted by reichman

Whoa. Avid shouldn't allow the automation of parameters that would impact the delay time that a 3rd-party plug-in reports to Pro Tools. I had no idea ADC could be updated during playback.

After a bit more investigation I found that almost every FabFilter plugin that allows you to automate parameters like oversampling, look-ahead have this problem. What baffles me is that the de-esser (which sounds great BTW) changes the latency even when you switch from wide band to split band. IMO, the plugin should report the maximum latency all the time and do all the necessary compensation necessary internaly. Other MFGs have different instances of the same plugin with different fixed latencies to avoid this (Sonnox surpressor, comes to mind). I awaiting FabFilter's response what they think about this. But for users of FF plugins I hope this warning helps. Frank.

[quadraphonics]

Frank,

I have experienced this in PT 11 and 12. In all cases it was due to a sudden automation switch happening at the start of a clip.

My normal work flow was to work in Preview, selecting the clip that I was working on, writing the automation and moving on.

Not often, but occasionally I would get clicks/pops at the clip boundary as a result.

Now I write the automation a few frames before the start of the clip and no longer have this issue.

Hope this helps.

Randall

Originally Posted by Frank Kruse

Hi,

today I had an issue where suddenly my work session would click and pop when playing low frequency content on one of my fx-tracks. First I had a glitch in a hidden automation lane in mind but there was nothing. The clicks where always in the same area but never in the exact same moment. So it could have been a drive issue. I copied everything to a new drive but the same thing happened.


Frank.

[Frank Kruse]

Originally Posted by quadraphonics

Frank,

I have experienced this in PT 11 and 12. In all cases it was due to a sudden automation switch happening at the start of a clip.

My normal work flow was to work in Preview, selecting the clip that I was working on, writing the automation and moving on.

Not often, but occasionally I would get clicks/pops at the clip boundary as a result.

Now I write the automation a few frames before the start of the clip and no longer have this issue.

Hope this helps.

Randall

Hi Randall,

thanks for your thoughts but that's a different issue. I am talking about pops resulting from the ADC engine switching compensation values on-the-fly (while playing!!!) because a plugin reports a latency change caused by automation even when there's no audio at all playing through the plugin. The pops come from tracks that don't even have the plugin on them. It's the ADC causing the pops. (see first posting)

The thing you mention is something different.

Frank.

[Frank Kruse]

FabFilter have responded saying that they will look into making latency changing parameters non-automate-able in the future.

Frank.

[dr sound]

Frank
I too had the same problem with the Fab filter Pro Desser .
It was the lookahead going into write by itself and I was't even using it.
It was random. You would hear it and then replay the exact same area over and it usually was't there but was slightly later or not at all then bingo, it was there again. I love the plug in and it only happens on Fab Filter with the Pro Deess and the Multiband. It is always the lookahead that is the cause of the problem. I'm going to NAMM today and if they are there I will discuss it with them.

[dr sound]

NAMM Update: FabFilter only had a local rep and not someone from the company at the show today. I discussed the issue with him and he promised me to let FabFilter know about the issue.