H/W Buffer setting not really affecting CPU Load?

[tmuzik]

No noticeable change in CPU load - with buffer settings from 128 to 2048.
Really super odd.

Check any session of yours - look at the CPU Load in the system meter with a 128 or 256 buffer then with a 1028 or 2048 buffer - was there a significant drop in cpu load?

There should be a significant difference in CPU load - I am not seeing a big difference anymore.

A session at 50-60% load with a 128 buffer, switching to a 1024 or 2048 buffer would normally give me a nice reduction of CPU load.

I cleared prefs -
I removed every single plugin (completely empty plugin folder on start) -
Tried all combinations of the tick boxes on the playback engine optimization page.


Please advise
Thanks

PT 2021.12
OSX Catalina
iMac i7
64GB
Focusrite 18i20

[weezul]

If nothing is record enabled then why would CPU usage change? Anything not record enabled is at 1024 buffer anyway? Record-enable some tracks and you will see the CPU usage increase.

[Ben Jenssen]

Tracks record enabled or not, I've never seen, in over twenty years w/PT, that the playback buffer size has any fundamental influence on CPU usage. The only relationship I see between the two is that as you reduce the buffer size toward the limit of what the computer can handle, the cpu usage indicator bars will become more and more unstable, more spikes, and eventually produce errors. You don't get a more capable cpu if you increase the buffer size. That's not how it works.

[tmuzik]

Originally Posted by weezul

If nothing is record enabled then why would CPU usage change? Anything not record enabled is at 1024 buffer anyway?

Thanks for responding.
CPU usage will change with the track count and plugin usage. Increased track counts and increased plugins demand more and more CPU cycles.

Your buffer is not always 1024. Your buffer should be set manually with your Playback Engine settings, depending what you are doing. - Traditional DAW usage scenario being lowest buffer your computer can handle for recording and highest buffer you can tolerate for mixing.

We are talking native system limitations here - not Carbon or HDX.

From the PT manual
The Hardware Buffer Size (H/W Buffer Size) controls the size of the buffer used to handle host based processing tasks such as processing with Native plug-ins.

Higher Hardware Buffer Size settings are useful when playing back and mixing sessions that use Native plug-ins.

It is a weird thing - on a 50%-ish CPU load session - not much of change on my system between 128 and 1024 - but if I drop to 64 buffer... BOOM instant redline overload.

The buffer change is happening and very much working - you can test with an instrument plugged in - It is just that the CPU is no longer taking advantage of the extra time it is allowed to process.

[DontLetMeDrown]

YES the buffer absolutely influences CPU since the DAW is working harder provide low-latency monitoring and playback, and this even affects the play button when no tracks are record armed. This is especially apparent when running a large session with lots of plugins on an older system- try playing it back at a 32 buffer.

I can see posters 2 and 3 are both using very fast systems, so that is likely why they may not be perceiving a difference, but Ben's last two sentences are objectively incorrect. You absolutely get a more capable system at a higher buffer. That's why most people have their buffer set low during tracking, then crank it high when they're ready to mix and add a ton of plugins.

OP, not sure what's the story in your case since its not clear to me how old your DAW is based on the OS.

[weezul]

Originally Posted by tmuzik

Thanks for responding.
CPU usage will change with the track count and plugin usage.

Of course, but it reads like you're expecting a difference between two identical set ups at different buffer settings with no record enabled tracks. Since PT11 there has been a separate playback buffer at 1024 at up to 48khz, it's listed in the PT11 user manual IIRC. That's all I was suggesting

[Ben Jenssen]

My point is quite simple; whatever the buffer size, the calculations being made are exactly the same, except with a larger buffer, the cpu has a little more time to do them. Hence the processor can 'relax' a little more, and fewer errors will occur. The number of calculations made are the same.

[tmuzik]

Originally Posted by DontLetMeDrown

OP, not sure what's the story in your case since its not clear to me how old your DAW is based on the OS.

Hi, agreed and thank you very much for your response
My system age doesn't really get to the heart of the issue (I will post full specs below) - I work within my limitations - it seems buffer calculations have changed.

I came across this b/c I have been compiling a list of plugins for a year or so and how resource heavy they are. In doing so. Each test must be as identical as possible.
I would always use the same session with the same buffer settings. Placing plug-ins across the same number of tracks or inserts and documenting the results via CPU system usage. (I know, not scientific and room for subjective error) It does not give exact numbers and cpu usage may bounce a bit, but I can get a ballpark as to which plugins are efficient which are heavy and which are absolute hogs.

It gives me a good idea of what I can reach for when recording vs mixing and what to expect from each plugin.

Basic Example:
88.2 256 Buffer - One stereo track (aux send) - 10 stereo aux - 1% CPU at play baseline no plugins active

Vallhalla VintageVerb x10 - 7-8%
ReLab SonSig A x10 - 22-26%
ReLab LX480 Complete x10 - 23-24%
BabyAudio Spaced Out x10 - 72-87%
Abbey Road Chamber x10 88-100%

I noticed this new buffer oddity because I created a more real world example of a session. I wanted to see worst case scenario (low buffer) vs mixing scenario (high buffer).
88.2 session - buffer = various - 32 stereo audio tracks (with my preferred base plugin chain) + 32 mono audio tracks (with plugin chain) + 10 active aux's of the same (whatever) plugin.
I get the same CPU usage with playback at 64 buffer as I do at 2048 - it was not like that before the last update.
If I arm a track with 64 buffer setting I get 100% spikes (expected) - But I shouldn't be able to do that with my system, why can I do that? It used to choke on 88.2 session with 64 buffer. Now it's good?

I am just curious at this point.

Avid is doing buffer magic or something is wildly wrong with my setup.

Am I possessed?

PT 2021.12
Model Name: iMac
Model Identifier: iMac18,3
Processor Name: Quad-Core Intel Core i7
Processor Speed: 4.2 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 8 MB
Hyper-Threading Technology: Enabled
Memory: 64 GB
Boot ROM Version: 429.140.8.0.0
SMC Version (system): 2.41f2

SOFTWARE
System Version: macOS 10.15.7 (19H1419)
Kernel Version: Darwin 19.6.0

HARDWARE
Focusrite 18i20

[LDS]

All modern DAWs run a dual sample buffer. One for recording as defined by the sample buffer option, and one for playback. There is nothing really to gain from running your playback tracks at lower than 1024 sample buffers. How effective Pro Tools has been at running dual sample buffers in the past, I don't know. But 2021.12 does it very well.

[tmuzik]

Originally Posted by LDS

All modern DAWs run a dual sample buffer. One for recording as defined by the sample buffer option, and one for playback. There is nothing really to gain from running your playback tracks at lower than 1024 sample buffers. How effective Pro Tools has been at running dual sample buffers in the past, I don't know. But 2021.12 does it very well.

Dual buffer? I did not know - I will need to investigate that. I have only ever had one buffer setting. Makes total sense, to separate playback/record.

What is odd is I can now record tons of inputs at 64 buffer @88.1 - I made a video showing how changing my buffer from 2048 to 64 does not change the cpu load what-so-ever, by the end I was recording 32 mono + 32 stereo w/ 64 sample buffer - it is crazy.

https://youtu.be/rUMzFY0AHz4

I also opened an old 44.1 session and I now have the option to go as low as 32 samples, I did not have that option in the past. I had always assumed it was because of my old audio interface and it's drivers.

I don't think my aging system is capable of that low of a buffer with that many tracks and plugins.