Dropouts from less than 100% load on CPU meter?

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zihlmannsven
Posts: 2
Joined: Fri Sep 01, 2017 12:48 am

Dropouts from less than 100% load on CPU meter?

Post by zihlmannsven » Thu Aug 09, 2018 12:38 pm

Hi!

I get nasty audio dropouts when Live shows only around 50-60% CPU while playing instruments through midi. If i increase the load it gets worse and when i reach around 80% it sounds like complete garbage. The most stable playback i can get is between 128 and 512 samples buffer size. I found really interesting that with 1024 and 2048 dependent on the playing it got worse than on the lower buffer sizes.

To eliminate the factor of midi interrupts i tried to load the CPU with an audio clip and a heavy chain of plugins until i heard dropouts. They were less present and i could definitively load the CPU a bit more without it sounding like complete garbage but i just don`t get it.

How is it possible that i am not able to max out Live`s CPU meter until the 100% mark before getting dropouts? How can i determine the source of the interrupts? I have a clean OS install on this machine with nothing but Chrome, Ableton and the soundcard`s drivers and mixing software installed. So i only used the stock instruments and plugins.

Hardware:
Macbook Pro 15 inch (Mid 2014, 2.5 GHz i7 4/8, 16GB RAM, GeForce GT 750M, 512GB PCIe SSD)
Fireface UCX (via USB)

Software:
macOS High Sierra (10.13.6)
Ableton Live 10 Suite (10.0.2)
Totalmix FX (1.50) / Firmware 46 / Driver 3.08

Any suggestions what i can do? To my understanding this shouldnt be a problem at all since it doesnt even use all the available resources for realtime processing.

Thanks!

doghouse
Posts: 1352
Joined: Fri Aug 29, 2008 5:30 pm

Re: Dropouts from less than 100% load on CPU meter?

Post by doghouse » Thu Aug 09, 2018 1:13 pm

That's normal with all DAWs. The CPU has more stuff to do than run Live. It's doing background tasks all the time, like monitoring the keyboard and mouse for input, disk I/O, audio and video drivers, network connections, etc. Both Windows and Mac OS have utilities that let you monitor what processes are running at any given time and how much CPU, memory and disk they are using. To get the highest performance turn off everything not needed...disconnect from the network, turn off wi-fi, see what startup tasks aren't needed, etc.

Stromkraft
Posts: 7055
Joined: Wed Jun 25, 2014 11:34 am

Re: Dropouts from less than 100% load on CPU meter?

Post by Stromkraft » Thu Aug 09, 2018 5:49 pm

zihlmannsven wrote:Hi!

I get nasty audio dropouts when Live shows only around 50-60% CPU while playing instruments through midi. If i increase the load it gets worse and when i reach around 80% it sounds like complete garbage.

How is it possible that i am not able to max out Live`s CPU meter until the 100% mark before getting dropouts? How can i determine the source of the interrupts?

Hardware:
Macbook Pro 15 inch (Mid 2014, 2.5 GHz i7 4/8, 16GB RAM, GeForce GT 750M, 512GB PCIe SSD)
Fireface UCX (via USB)

Software:
macOS High Sierra (10.13.6)
Ableton Live 10 Suite (10.0.2)
Totalmix FX (1.50) / Firmware 46 / Driver 3.08

Any suggestions what i can do?
There seems to be a Flash Update Tool for Firmware 47 of 11th of July.

With Live 9 dropouts in my experience may come already at 70% audio engine load, in Live 10 it's more like 90% for me but it depends on the instrument. I have some demanding plug-ins.

How many channels do you have active in the UCX? That draws CPU, used or not. Have you talked to RME? They often have great suggestions.

If you don't use an external monitor, or a Push 2, you may want to look into using the internal graphics only.

Personally, I don't trust High Sierra. You formatted like APFS or kept HFS+?
Make some music!

fishmonkey
Posts: 4023
Joined: Wed Oct 24, 2007 4:50 am

Re: Dropouts from less than 100% load on CPU meter?

Post by fishmonkey » Fri Aug 10, 2018 10:57 am

zihlmannsven wrote: I get nasty audio dropouts when Live shows only around 50-60% CPU while playing instruments through midi. If i increase the load it gets worse and when i reach around 80% it sounds like complete garbage. The most stable playback i can get is between 128 and 512 samples buffer size. I found really interesting that with 1024 and 2048 dependent on the playing it got worse than on the lower buffer sizes.

To eliminate the factor of midi interrupts i tried to load the CPU with an audio clip and a heavy chain of plugins until i heard dropouts. They were less present and i could definitively load the CPU a bit more without it sounding like complete garbage but i just don`t get it.

How is it possible that i am not able to max out Live`s CPU meter until the 100% mark before getting dropouts? How can i determine the source of the interrupts? I have a clean OS install on this machine with nothing but Chrome, Ableton and the soundcard`s drivers and mixing software installed. So i only used the stock instruments and plugins.
firstly, the Live "CPU" meter isn't really a CPU meter at all. i think it would cause a lot less confusion if Ableton called it something else:

https://help.ableton.com/hc/en-us/artic ... sk-Manager

secondly, the amount of CPU power being used doesn't always correlate with actual audio processing performance. that is because glitch-free audio first and foremost requires solid, uninterrupted audio processing to occur. audio can even glitch on a computer that shows very low CPU usage—i.e. there is plenty of power, but it cannot be harnessed smoothly enough because other processes are stalling audio processing for too long. the problem is that audio processing requires real-time performance, and Mac OS X and Windows are not real-time operating systems (a proper real-time operating system can guarantee processing time to specific processes).

it makes sense that you can load the "CPU" meter higher with an audio clip, since the amount of audio processing power required is more stable. if you are playing a virtual instrument via MIDI, then the amount of processing power required can vary greatly depending on the instrument you are using, and how many notes you are playing concurrently—this is probably why it seems more unpredictable to you.

this Ableton help page covers most of the things you can do in Live to reduce CPU load:

https://help.ableton.com/hc/en-us/artic ... e-CPU-load

there are some helpful tips on that page, however there is not a lot of detail about other Mac OS X processes that can cause glitches. this guide covers most of those:

https://figure53.com/docs/qlab/v3/gener ... -your-mac/
smutek wrote:For an ever lasting sound ... turn sustain, decay and release all the way up and lay a brick on your keyboard. You also want to leave your computer on for this. Don't move the brick.

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