Delay compensation bug after Pro Tools update.

[quadraphonics]

All,

I updated one of our Pro Tools systems here from 10.13.6 and PT 2020.12 to 10.14.6 and PT 2021.12 (The last officially supported PT for that OS). We cannot go up to 10.15+ because there is a bug that changes the color space on Pro Res videos bounced out of Pro Tools(up to current). This is a big part of our workflow here.

I have noticed an odd playback bug. After bouncing a 5.1 program, I attempted to phase cancel against the mix session. The mix phase cancelled completely against the source EXCEPT the dialogue stem. In this case, the dialogue stem is the stem showing the greatest delay compensation (1500-ish samples).

When zooming in, the 5.1 printed in sync with the dialogue in the stem, down to the zero-crossing points.

This was with the Hybrid engine on.

With the hybrid engine off, the music and effects still cancel out, but there is now an audible slap between the dialogue from the mix session and the printed 5.1

What is going on and does anyone have any tips to solve this?

This does not happen in 2020.12. The printed 5.1 phase cancels 100% against the mix session.

Thanks,
Randall

[Reckless Erik]

Sounds like you have exceeded the delay comp on your DX stem. Are any tracks showing red in the delay comp values?

[quadraphonics]

Erik,

Thank you for responding. There are no tracks with red delay compensation values.

This session is really basic. It is 3 5.1 stems (DME), which all feed individual sub busses.

Only one of the sub busses is showing any delay compensation (DX at 1536(green)).

Randall

Originally Posted by Reckless Erik

Sounds like you have exceeded the delay comp on your DX stem. Are any tracks showing red in the delay comp values?

[its2loud]

I noticed a similar experiencing yesterday on a 5.1 session. I’m going to conduct more testing with a previous version of PT. No obvious delay comp exceeded and it was only happening on the PM and none of the stems.

[quadraphonics]

Which version of PT are you running?

Originally Posted by its2loud

I noticed a similar experiencing yesterday on a 5.1 session. I’m going to conduct more testing with a previous version of PT. No obvious delay comp exceeded and it was only happening on the PM and none of the stems.

[its2loud]

2022.12. I misread or original post of 2021.12 as 2022.12 so my issue may or may not be similar.

[quadraphonics]

It sounds like the same issue. Also, it kind of confirms that my upgrading to 2022.12 would most likely not solve my issue.

Randall

Originally Posted by its2loud

2022.12. I misread or original post of 2021.12 as 2022.12 so my issue may or may not be similar.

[its2loud]

I don't think the issues are related. Mine was a delay compensation overload that I wasn't seeing when arming all 20 tracks for printing stems. When I did an offline bounce everything synced up fine.

[LDS]

This has been my experience ever since the introduction of the Hybrid engine.

[Darryl Ramm]

Originally Posted by quadraphonics

All,

I updated one of our Pro Tools systems here from 10.13.6 and PT 2020.12 to 10.14.6 and PT 2021.12 (The last officially supported PT for that OS). We cannot go up to 10.15+ because there is a bug that changes the color space on Pro Res videos bounced out of Pro Tools(up to current). This is a big part of our workflow here.

I have noticed an odd playback bug. After bouncing a 5.1 program, I attempted to phase cancel against the mix session. The mix phase cancelled completely against the source EXCEPT the dialogue stem. In this case, the dialogue stem is the stem showing the greatest delay compensation (1500-ish samples).

When zooming in, the 5.1 printed in sync with the dialogue in the stem, down to the zero-crossing points.

This was with the Hybrid engine on.

With the hybrid engine off, the music and effects still cancel out, but there is now an audible slap between the dialogue from the mix session and the printed 5.1

What is going on and does anyone have any tips to solve this?

This does not happen in 2020.12. The printed 5.1 phase cancels 100% against the mix session.

Thanks,
Randall

There seems a few ways Pro Tools can mess up with large delay compensation errors: where an incorrect delay compensation equal to the disk playback buffer (not H/W buffer) is applied (so 1024 or 2048 samples depending on sample rate). These issues might all trace back to the same root cause. If you pull off other plugins in that track's delay comp chain I suspect you may see exactly 1024 samples latency (and I assume you are at 44.1 kHz or 48 kHz? so a 1024 sample disk I/O buffer). It may be worth making a copy of your session that you can hack up to do that and more to play here.

These problems may have been introduced when Avid added "Allow Sends to persist during LLM" but IIRC that was in 2018.7 so the same bug might have been in 2020.12, but maybe you had different preference settings and were not seeing the bug. I have also not gone looking back at behaviors in past Pro Tools releases. The problem other folks have seen are manifest in one case where you have a H/W insert following a plugin, have "Allow Sends to persist during LLM" enabled and have LLM on. Disabling LLM or "Allow Sends to persist during LLM" in that case avoids the problem. This is Pro Tools bug PT-293686 been reported to Avid for months now, with trivial way to reproduce. There are other ways a similar delay comp error can occur.

I'm a complete idiot when it comes to hybrid engine, have never used it, etc. (please send me some HDX cards and a MTRX and I'll explore this bug for ya all ). But for the heck of it you could try disabling "Allow Sends to persist during LLM" and LLM if they are even options (makes sense they could/should be but I am not sure) and see if this changes the behavior.

Of course there may be other issues, plugins with broken delay comp, yet some other Pro Tools delay comp issue, some weird issue with routing, etc. but it would be great just to see if what you are seeing might be related to these other known problems.