Hello All
Looking for tips and feedback. My goal is to understand System Usage “CPU” monitor as it relates to trouble shooting my problem. I am also trying to understand what some of the contributing factors are when I get audible dropouts, glitches and stutters working with small H/W Buffer Sizes 64/128 samples.
When I hear these audible errors I can see my CPU in system usage has spiked. I even get this while the transport is parked with ProTools in "idle" I can hear aux input sources drop and stutter. I have experienced this on both Mac and Windows hardware (using the same Native Card).
At larger H/W Buffer Sizes (512/1024) the system works well however this is not a good option for me, I need low latency. A critical part of my workflow is to input monitor then re-record external sources through the HD hardware into my Pro Tools session often against picture.
My current test conditions are :
Hardware - Windows 10 (up to date), i7 7700k, 16gig ram, SSD's, on board Intel HD Graphics 630, Intel B250 chipset. This system passes all stress tests.
Software - Pro Tools 2018.3.0, HD license on iLok2, everything is up to date. Eucon latest versions installed. Avid Dock and iPad latest versions installed.
Test Session 1 (Bare)My test session is setup like this : 8 Stereo audio tracks input from HD Hardware output to my 2.0 Monitor path with 2 Aux Input also set to my 2.0 Monitor path. There are no plugins inserted on any track. Eucon turned off in settings, HUI turned off in settings, GEN MTC off (using Video slave 3). Hardware clock set to internal HD I/O. Playback engine HD Native H/W buffer Size is 64 Samples. Ignore errors unchecked, Dynamic Plugin Processing Unchecked. Video engine disabled. Disk playback 4Gig. Delay comp is on but the tracks report 0 because there are no plugins. Unique 1min pink test file created on each track using audio suite signal gen.
Observations using this ultra bare bones session are .. well unexpected. I am seeing a jump in CPU based on if Pro Tools is the in focus application. I do not hear any audible problems.
ProTools in focus
[System Usage reported by Pro Tools]
At idle CPU shows 10%.
Playback CPU shows 10%.
Scrolling the mixer window CPU shows 30% and spikes at 50%
Windows desktop application (browser, other app etc) in focus.
[System Usage reported by Pro Tools]
At idle CPU shows 20%.
Playback CPU shows 30%.
Scrolling or resizing windows desktop app CPU shows 50% and spikes at 80%.
Clearly on my system bringing a Windows desktop app into focus causes a jump in CPU and resizing / scrolling we see massive jumps. (possibly related to the on board video Intel HD 630)
What’s confusing is when you open the windows task manager performance tab side by side with Pro Tools System Usage. In Windows you need to show more details with the view of the expanded graph for CPU. This graphs CPU performance as reported by windows.
Now if we repeat the simple tests above (idle, playback, scrolling) we can see there is a disparity between the Windows graph and the ProTools System Usage. Pro Tools reports CPU spikes that the windows performance monitor simply cannot detect. OK so we know Pro Tools and Windows CPU monitors are not “in sync”.
Test Session 2 (Full)To take this concept even further I loaded up a full session. It’s not that big 60 voices for example, avid channel strip on all tracks and “Pro” plugs on my bus masters, I was careful to look at the delay comp reported by plugins and have been able to get this session delay comp down to 40 samples even with reverbs etc. All the other settings as per Test Session 1, it simply cannot run at a H/W buffer of 64 with System Usage hitting 100%. Windows CPU monitor however never goes above 30% !! It’s with a full session where I can see a big difference between what Pro Tools and Windows report for CPU. (see screen shot attached). 
Regardless of CPU usage reported by Pro Tools, Windows never reports more than about 30% - 35% even while Pro Tools is the in focus application.
Ok let’s get this session working so we can discover some more performance issues. I have to set the H/W buffer at 256 so the session is now operable. Pro Tools is the “in focus application” because we know that if it’s not we get poorer performance.
At Idle.Pro Tools = 30%
Windows = 30%
Playback.Pro Tools = 40%
Windows = 30%
Scrolling Pro Tools mix / edit.Pro Tools = 50%
Windows = 30%
Pro Tools in focus Input monitor my SFX record tracks.Pro Tools = 70%
Windows = 30%
Recording and editing SFX switching Input as needed.Pro Tools = 70%
Windows = 30%
Let’s add back in bringing a Windows app into focus.Pro Tools = 50%
Windows = 30%
Operating at H/W Buffer 265 seems OK .. however ProTools regardless of it’s state (idle, playback, in focus, input monitor) randomly throws 100% usage. So I’ll be sitting working on something in the studio quietly listening to some music and I hear [[glitch, drop, pop, brrrrrppptt]] and Pro Tools throws an error. That is disruptive to say the least. The only fix is to set full sessions at 512 H/W Buffer with is noticeably laggy.
So now I have a few questions …
- Is the disparity between the Pro Tools CPU and Windows CPU reporting expected ?
- Is Windows clamping Pro Tools CPU use to 30%? Is it possible to unleash the other 70% of my actual CPU power or is this just misreported ?
- Why does input monitor take more CPU ? Is there some way to work around this or fix it entirely ?
- Why does changing application focus take more CPU ? Is there some way to work around this or fix it entirely ?
Sorry my signature is out of date .. please ignore