25% CPU usage increase on input monitoring

[wonder6oy]

Ok - I tried that out (substituting Aux tracks for Audio tracks with input monitoring engaged) and ended up getting the exact same results. So it's not exclusive to Aux tracks! Interesting.

clancychris, I think this would help explain the similar behavior regarding your situation.

[clancychris]

Originally Posted by wonder6oy

Yesterday I sent another test session to a friend of mine who mixes on a Mac (I'm on PC). The session allows you to check the difference in the number of plugs you can run on individual audio tracks vs how many you can run on a series of busses. The difference on both our systems was both similar and staggering. On his (a 2015 iMac), he can run over 400 Pitch II instances on just the audio tracks and maintain total stability during playback, but when he moves the plugs from the audio tracks to the aux busses, that number drops to a remarkably low 80 instances. On my machine the results are similar: on audio tracks, I can get to 340 instances running smooth vs only 77 on the aux tracks. In both our cases, that's over a 400% increase in CPU usage on the Aux busses! He was as stunned about this as I initially was, and began to recognize in retrospect where he had faced work-halting issues in the past that might easily be explained by this phenomenon.

Is it a bug? Bad code? A feature "restriction" gone unmentioned by Avid? I don't know.

But I do know what it's NOT.

-It's NOT poorly coded 3rd party plugins (and yes - I even tried moving them out of the plugins folder)
-It's NOT a lack of power
-It's NOT a lack of memory
-It's NOT a hard drive issue
-It's NOT a neglect to follow optimization procedures from Avid or anyone else
-It's NOT a denormalization issue
-It's NOT a licensing check issue
-It's NOT a Dynamic Plug-in Processing issue; the problem persists with or without it
-It's NOT a Delay Compensation issue (I can get the same disastrous results with only 8 (yes 8) instances of Scheps Parallel Particles and a grand total of roughly 595 samples of PDC going on.
-It's NOT an unreasonable choice of workflow

And, given the reproducible symptoms across both Mac and PC platforms:

-It's UNLIKELY a driver issue
-It's UNLIKELY due to faulty hardware
-It's UNLIKELY the fault of the OS

So what is it?

Here's that session btw...
https://www.dropbox.com/s/9zrf9qm8py...test1.ptx?dl=0

Results for this:

On a 2010 8 Core Mac Pro 2.4 with 32 gig ram:

Test 1: I can run one instance of signal gen and 6 instances of Pitch II on each audio track before hitting instability. (total of 420 Pitch II's and 68 Signal Gen)

Test 2: I can run one instance of signal gen on each of the 68 audio tracks, and then 39 instances of Pitch II and then it goes nuts. - note: i enabled them in rows.

So that's a fair difference and explains why I'm having issues

[dankin]

I think your issues are related to the dual buffer. I can't think of any other reason there would be such a big difference in CPU between running plugins on a track vs a aux. I'm wondering if this is also part of what causes the infamous 9173s that we've been plagued with since 11 was introduced?

[clancychris]

Originally Posted by dankin

I think your issues are related to the dual buffer. I can't think of any other reason there would be such a big difference in CPU between running plugins on a track vs a aux. I'm wondering if this is also part of what causes the infamous 9173s that we've been plagued with since 11 was introduced?

I totally agree. Can anyone open this test session up in PT10?

[wonder6oy]

Originally Posted by dankin

I think your issues are related to the dual buffer. I can't think of any other reason there would be such a big difference in CPU between running plugins on a track vs a aux. I'm wondering if this is also part of what causes the infamous 9173s that we've been plagued with since 11 was introduced?

Did a little looking into the dual buffer feature. I agree that it's possible that it could be tied to this issue somehow, but it baffles me why on earth you'd want the lowest possible latency (coupled with the highest CPU usage) to occur on anything - audio track, aux track or otherwise - that isn't being fed a live input.

Then again if we're looking at this to be the cause, it would only moderately increase the amount of power needed from the CPU, which doesn't really explain the unstable spiking behavior.

[clancychris]

Originally Posted by wonder6oy

Did a little looking into the dual buffer feature. I agree that it's possible that it could be tied to this issue somehow, but it baffles me why on earth you'd want the lowest possible latency (coupled with the highest CPU usage) to occur on anything - audio track, aux track or otherwise - that isn't being fed a live input.

Then again if we're looking at this to be the cause, it would only moderately increase the amount of power needed from the CPU, which doesn't really explain the unstable spiking behavior.

Check this out for a weird thing. A friend just asked me to try it.

Open a session and take note of your CPU usage. Then put a hardware insert on the Master Bus. Anything will do, if you don't have hardware just make it anyway and try it.

My CPU usage falls by 20%+ instantly. Just by putting the insert there

[wonder6oy]

Originally Posted by clancychris

Check this out for a weird thing. A friend just asked me to try it.

Open a session and take note of your CPU usage. Then put a hardware insert on the Master Bus. Anything will do, if you don't have hardware just make it anyway and try it.

My CPU usage falls by 20%+ instantly. Just by putting the insert there

I used to encounter this using Pro Tools 10 years ago, but my current interface is limited to 2 channels so I am unable to try this again atm. But that's something I can change if need be. Can you try this on the session I uploaded and let me know if it makes a difference?

[wonder6oy]

I found a way to try that here with another interface (insert at the end of the chain). Results still remain unchanged though. I had high hopes for that idea too, given my past experience.

[[email protected]]

Originally Posted by wonder6oy

I found a way to try that here with another interface (insert at the end of the chain). Results still remain unchanged though. I had high hopes for that idea too, given my past experience.

I'm in the same boat over here. My mix sessions are set to 1024 buffer and when my print track is in input, session jumps about 25%-30%. Sometimes cripples the whole session.

[clancychris]

Yeah also tried it. In this situation it makes no difference to it