Buffer issue using Serum 2

[u/priz123]

I was playing around in Serum 2 today, so I opened a fresh project and loaded a few instances but when I opened my third I noticed cpu was spiking to 80-90% and the audio started cracking. I figured it was a cpu issue but after checking activity monitor it showed 81% idle yet ableton running at 300% cpu.. I’ve never had issues with this machine before, especially with such a small project, usually I don’t face issues like this until I have a 70-80 track project with multiple instances of Serum 1. I tried using a buffer size of 1024 and 2048 samples and increasing it didn’t help.

Can anyone explain what’s going on here and if there’s anything I can do to prevent it in the future? I’m on a 2020 iMac if that makes a difference

[u/abletonlivenoob2024]

fyi: Lives CPU meter and your OS activity monitor do not measure the same thing.

With Serum2 having the potential to be way, way, way more CPU hungry than it's predecessor it can very easily max out the single core performance of your intel processor (Live does not use multiple cores for a single track)

https://help.ableton.com/hc/en-us/articles/360019151379-Live-s-CPU-Meter

https://help.ableton.com/hc/en-us/articles/209067649-Multi-core-CPU-handling-FAQ

P.S.

To some extent Serum2 is built with future CPU performance gains in sight - maxing out the unison and spectral synthesis features can easily bring even not that old CPUs to its knees (thou as to the documentation Serum1 patches should use less CPU on Serum2...)

[u/priz123 → u/abletonlivenoob2024]

Thanks for the info! I’ve spent over 10 years on Live and never knew this. But after reading through the help posts I’m still no closer to figuring out how to prevent this

[u/stschoen → u/priz123]

It's an issue with Serum2 not Live. Other than using a different synth plug-in or downgrading back to Serum1 (if that's even possible) your only recourse is a faster CPU.

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[u/Doc_da_Seltzam]

Check out LatencyMon and run a test.

Check out the ISR routine execution time and the DPC routine execution time.

It should be lowest as possible.

Maybe there is an issue. If it is, your realtime audio processing will be affected.

[u/Winter_Money_9282]

macOS's Activity Monitor shows percentage per core used, for example if you have a 10 core CPU,  1 core maxed out would be 100%, where all 10 cores would be 1000%. It is odd, but thats how macOS displays per app usage statistics.

Ableton shows processing percentage for a single buffer. Per Ableton's website:

"Live's CPU Meter value is not the same as the percentage of overall system CPU used by Live shown in macOS Activity Monitor or Windows Task Manager. For more information, see the dedicated article Monitoring Live’s CPU usage on your computer. Here is an overview of the CPU Meter value:

• Live measures the time needed to process each audio buffer and compares it to the time it takes to play one audio buffer. For example, 50% on the CPU Meter means Live's processing of one audio buffer takes half as long as it takes to play this buffer.
• Values over 100% are possible; this means that the processing takes longer than playback, which is likely to result in audio interruptions.
• Because they may impact the processing power available to Live, other applications and computer processes can cause CPU spikes in Live's CPU meter.

As of Live 11, when Live's CPU Meter display is set to "Current," the measurement is more active compared with Live 10. This is expected, as the Meter displays peak CPU usage with this setting. The CPU Meter in Live 10 only measures average CPU, which results in less extreme fluctuations."

Serum 2 on the other-hand, Steve Duda, the developer has stated that intel performance is not up to par with the previous version, but updates should fix the issue. If I could remember the source from where I found this tidbit, I'd absolutely share it, but I do not remember where I had found this information from.

I'd expect over the next few months there to be updates for serum 2 to bring CPU usage down and general performance improvements.