Be aware of these Plugin Delay Compensation Fails

[FMN-Music]

These are the areas where PDC is broken:

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0:00 Sidechain in Groups
2:31 VST Instruments in serial
3:42 Hardware Inputs
6:18 Multi Instruments
7:03 Batch Processor


- Aux Channels linked to external Instruments
(https://studiooneforum.com/threads/delay-compensation-for-external-instruments.733/)

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0:00 Sidechain PDC Issue in AUX Channel for External Instrument
2:11 Rendering External Instruments AUX Channel vs. just recording the Input onto an Audio Channel (This is not a PDC issue, it is an Interface Process Buffer Compensation issue)

 

[Navar]

These are the areas where PDC is broken:

Just for curiosity, did you check, if the plugin on the ListenBus makes any difference? Several versions ago, I had a problem with the SC PDC when something was on the Listen Bus.
And? Is it just me or are some problems are just coming back which were already solved? The sidechain pdc problem is not new too me but was fixed several versions ago.

 

[FMN-Music]

What has been fixed a few versions ago was the Sidechain PDC in Tracks, but when Busses are involved PDC can still break.

If you use Sidechain on a plugin, inserted in the Listen Bus and move a latency inducing plugin before or after that, then you get the same result as shown in the second part of the "Sidechain in Groups" chapter. Plugin Delay Compensation of the Sidechain Signal breaks. It kind of makes sense, because the Listen Bus is basically a Bus, so it suffers from the same problem as the other Busses.

 

[Navar]

What has been fixed a few versions ago was the Sidechain PDC in Tracks, but when Busses are involved PDC can still break.

If you use Sidechain on a plugin, inserted in the Listen Bus and move a latency inducing plugin before or after that, then you get the same result as shown in the second part of the "Sidechain in Groups" chapter. Plugin Delay Compensation of the Sidechain Signal breaks. It kind of makes sense, because the Listen Bus is basically a Bus, so it suffers from the same problem as the other Busses.

I did the test myself with your setting, and I could replicate this with MUtility but with some other plugins not. I did the exact same test with Fabfilter L2 after the Sidechain input with 32x Oversampling which adds 65.5ms of latency. And I've typed in 65 ms in MUtility. L2 gets compensated, MUtility not, clear audible and can be reproduced. Tested it with the latest version of the Melda plugin.

 

[FMN-Music]

Please make a video, if you can. I have no problem to replicate the Test with Pro-L 2.

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[Navar]

Please make a video, if you can. I have no problem to replicate the Test with Pro-L 2.

I don't have a screen capture software installed right now. But I did several rounds of flipping things around and here is what it does on my side. I have to correct my message before, I was using V7 for this.

- V7 works nearlly all the time on my side, sometimes if I move the plugin around between bus and channel, it doesn't seem to take the pdc with it. Start-Stop sometimes fix it, deactivating and activating the plugins fixes it. But it doesn't seem to be 100% reliable.
- V8 has more problems indeed as you said. It seems that the latency of the plugin on the channel/track does not get forwared to the sidechain on a bus. Plugins with latency on a bus before the sidechain does it again, but deactivating the whole chain on the bus and re-activating it, fixes this behaviour on my side.
- Moving plugins around when the playback is running seems to have a general problem with the latency compensation and sidechain in general, sometimes my signal doesn't even go through the SC anymore, sometimes the pdc is broken.
- Melda Utility forces pdc problems any time, the latency is shown in the performance view and in the overview but in V7 and V8 the latency does not get compensated. In my personal opinion there is a problem with this plugin which has nothing to do with the general problem, or it's the best way to reproduce this any time.
- This thing can be reproduced with internal Fender / SPro plugins only, I've tested it with Pro EQ in Linear Phase Mode (33ms latency and audible) and the Gate which has a sidechain filter listen function.
- Changing bit resolution, dropout protection, plugin nap or anything like that doesn't change anything.

 

[js1]

What has been fixed a few versions ago was the Sidechain PDC in Tracks, but when Busses are involved PDC can still break.

If you use Sidechain on a plugin, inserted in the Listen Bus and move a latency inducing plugin before or after that, then you get the same result as shown in the second part of the "Sidechain in Groups" chapter. Plugin Delay Compensation of the Sidechain Signal breaks. It kind of makes sense, because the Listen Bus is basically a Bus, so it suffers from the same problem as the other Busses.

Just curious, what's the use case for using a plugin with sidechain on the Listen bus?

 

[FMN-Music]

You'll need to ask Navar.. but, does it matter?
If your car engine under some circumstances starts running unevenly and you can also showcase the issue by doing something nobody would do while commuting, the engine still needs fixing, right?

 

[Navar]

Just curious, what's the use case for using a plugin with sidechain on the Listen bus?

You'll need to ask Navar.. but, does it matter?

No, not in my case, it was just a thing which happened long time ago where plugins on the Listen Bus with latency caused problems with the latency compensation. But that's not the case here, doesn't matter, sorry if this was misleading from my side.
What I've seen so far, there is a huge problem with the latency compensation in V8 in some situations which can't be avoided if you work with sidechaining and for me personally this is acutally a showstopper.

 

[FMN-Music]

I agree. It is quite annoying to be mindful of this, whenever timing sensitive Sidechain is in use.. which in Music is pretty much always the case..


Since the devs need to crack open the ol' audio engine anyways, because of the "Double Precision Debakel" it might be a good opportunity to have a look at this as well... one can hope

 

[Rambler]

If I understand right this problem has existed before SP8, so it will happen in SO7 (and maybe earlier versions) as well?

 

[Navar]

If I understand right this problem has existed before SP8, so it will happen in SO7 (and maybe earlier versions) as well?

In my personal opinion not quite as reproducable as in SP8. I use sidechain on busses nearly in every song in V7 and everything is fine on my side. I normally do classic sidechaning of gates, bass&bassdrum, snare&guitars, pumping fx and all those stuff.

Here are 2 extremly simple test songs, just based on pro eq and gate. Both are created in V7 & V8 so it's not only an "opened in V8". Zip Files are around 100kB.
V7: works on my side

Sidechain Plugin Latency V7.zip

drive.google.com

V8: fails every time

Plugin Latency Compensation Failure V8.zip

drive.google.com

This is the setup, takes 1 minute to reproduce.

@FMN-Music : you've opened up a ticket already with an example song file and so on?

 

[FMN-Music]

@FMN-Music : you've opened up a ticket already with an example song file and so on?

I have not, feel free to do so.

If I understand right this problem has existed before SP8, so it will happen in SO7 (and maybe earlier versions) as well?

Yes, these are known problems from the past.

 

[Rambler]

I have not, feel free to do so.



Yes, these are known problems from the past.

That's quite staggering since this is not a minor bug but something that's fundamentally affecting the way your productions will sound. Especially since you might not always hear it at lower latencies but just feel that your sidechaining isn't as tight timing-wise.

 

[Navar]

A short update on this one, I had a nice conversation with the support and they are aware of this and the status is work in progress.