Compensate Input/Output Delay with external converters – not H/W Insert delay!

[Darryl Ramm]

Originally Posted by NoBruno

Thanks for the suggestion, Darryl. I created a minimal session and measure the time delay as 2 ms. Here was my process:

• Create minimal Pro Tools session with no plug-ins except a single instrument to generate a click
• Play click track out through hardware output 8 of MOTU 896mk3
• Cable output 8 to input 8
• Record input to an audio track in Pro Tools
• Compare original click and recorded sound
• Recorded sound is 2 ms late

Attached screen shot shows:

• Original click instrument track
• Committed version of same
• Internal bounce of click (send to internal PT bus and use same as input to a new audio track -- timing is sample accurate with committed track)
• Analog signal recorded as noted above - 2ms late

That seems like way more than it should take to go DA/AD, but it is within an acceptable range and if the delays were consistent, I would go on my merry way. However, my problem is that I am experiencing different delays at different times. With the same session (all the same tracks, I/O, plug-ins, etc.) I have experienced delays between 2ms and 45 ms. Most of the time, it's 2ms, but there are times when I record an overdub and it is obviously out of time. In those cases, when I immediately run a test per the above, the delay is closer to 45ms. Since the results with the exact same session are not consistent, it is very difficult to figure out the cause. The fact that I measure 2ms with my minimal session may have nothing to do with it being minimal since most of the time more complex sessions perform just as well. It is possible that if I spent long enough in the test session recording and listening to clicks, it would eventually deviate as well, I just don't think my soul could endure that.

As all intermittent behaviors, this one is pretty difficult to troubleshoot so any further suggestions are truly appreciated.

I missed your reply before.

This absolutely does not happen for me. I get sample accurate behavior (most 6 versions of Pro Tools, most recent three major releases of macOS, three different RME interfaces). But you are skipping over some stuff about how exactly you do things, like what exact track was committed and why did you do this? Is that related to a problem you are trying to solve? If not can we focus on what is the absolute minimum test that shows the problem. Like if you just record click bussed to an audio track and click out and back into the interface

More info would probably help.

Confirm you are not using aggregate I/O

Does enabling or disabling latency compensation make any difference here?

What are your main outputs that you are monitoring though while doing all this? I want to make sure there is a separate main audio monitoring path, and it does not involve output 3.

Make sure you are not in LLM mode, or if you have been test again without. There is at least one known bug with LLM and some hardware insert and plugin combinations badly borking delay hardware insert compensation, maybe there are other problems with LLM.

Do you have another interface to test with?

Can you share a copy of your session.

You say the latency varies, I think you have to keep trying to work out what you change to get it to vary. Any chance it's sample rate? Or wether LLM is enabled? Or...

If you are willing I'll can also get you to run a test on the interface RTL and some other reported latency independent of Pro Tools. We can take that offline.