Severe bug when Input Monitoring with mono-to-stereo plugin (even when bypassed)

[XJENSEN]

Dear friends,

Request for help. I have been running into (variants of) this problem for quite a while now...

I also opened a ticket with Avid support, but I'd like to ascertain/confirm that the problem I'm seeing is (not) specific to my system. Or any other clues I may get.

I will attach the session. Greatly appreciate anyone willing to give it a quick try and report back!

Situation on my system: (Mac OS 10.14.6, Pro Tools Ultimate 20.9.1)
- I recorded two audio tracks: a clean and a noise signal.
- The clean signal (first track) is feeding the second audio track input through a bus.
- When I enable the Input Monitoring on the second audio track, I don't just hear the input track (the first audio track) but also the second audio track's audio, which should not be the case. I should only hear the input track.
- Moreover, the input audio is panned hard left and the audio on the second track is panned hard right on my monitors when I engage Input Monitoring.
- Deleting the mono-to-stereo reverb plugin on the second audio track clears the problem! So it seems to have something to do with mono/stereo paths being messed up when engaging Input Monitoring.

Has anyone else experienced this? Can anyone confirm the same behaviour with this session on your system?

I would greatly appreciate anyone willing to give this a short try (should only take a few minutes) and provide feedback.

Best regards and stay safe!
Xavier

[XJENSEN]

And here's a movie showing the hooky spooky: https://drive.google.com/file/d/1h16...ew?usp=sharing

It seems:
- The input monitoring is sending everything through the left path only.
- It is not properly muting the original track audio, which is still passing through.

[64GTOBOY]

I haven't tried your session yet and i am on Windoze now but i have had pan and routing issues when using certain plugins.

Usually re installing and cleaning preferences fixes it, though sometimes i have had to create a new audio track and move the original audio to the new track. I don't know why that works.

In other situations i have found it was the stereo version of the plugin causing issues which was solved by changing to dual mono version(if available)

[JGuth]

Have you tried different mono to stereo plugins ?? Odds are the plugin is the culpret.

[XJENSEN]

Thanks for the tips. I was just using the stock DVerb plugin. Also tried on a completely new partition with only Mac OS and Pro Tools, and behaves exactly the same there.

I also commented earlier in some other post that there could be a problem with the Waves Tune plugin, as I was also getting phasing there. Now I'm starting to think that was also related to Pro Tools rather than the Waves plugin..

Will do some more tests. At the moment, I don't have the feeling that I can 'trust' the Pro Tools software anymore. Constantly checking if everything is behaving properly..

[XJENSEN]

Interesting observation after further testing: The DSP versions of the plugin seem to work better, in the sense that they block the signal path of the original track audio, so also the right channel.

The Native version of the plugin does not work the same and lets through the right part of the original audio.

But, even with the DSP version, the audio only passes over the left channel of the (to stereo converted) audio track in input monitoring.

Something is very wrong here.

[Darryl Ramm]

I get no problem when testing this session on 2019.9.1 on a MacBook Pro using Built-In Output.

What happens when you get rid of the Omni and use Built-in Output/MacBook Pro Speakers. Is low latency monitoring/the hardware mixer in the omni causing you issues? (I'm not following exactly how it would, but I suspect built-in output is the next logical test for you).

[Ben Jenssen]

Originally Posted by XJENSEN

- When I enable the Input Monitoring on the second audio track, I don't just hear the input track (the first audio track) but also the second audio track's audio, which should not be the case. I should only hear the input track.

I agree.
And that's what's happening here. I have your session up and it's behaving like it should. And when bypassing the Dverb, I still hear either track 1 or 2 according to input button setting on or off. No mix of the two like you describe.

[XJENSEN]

I greatly appreciate you testing, thanks! Would love to collect some more data points.

I do see we have a fairly different setup, however.

[XJENSEN]

Originally Posted by Darryl Ramm

I get no problem when testing this session on 2019.9.1 on a MacBook Pro using Built-In Output.



What happens when you get rid of the Omni and use Built-in Output/MacBook Pro Speakers. Is low latency monitoring/the hardware mixer in the omni causing you issues? (I'm not following exactly how it would, but I suspect built-in output is the next logical test for you).

Very good suggestion. I will try that ASAP.