Live performance - 24bit vs 16bit in Cubase?

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Live performance - 24bit vs 16bit in Cubase?

Post by c_h_music »

Hi all, my performance setup is built on Cubase, which handles some midi, automation, prerecorded tracks and realtime VST instruments, as well as input channels that go through VST effects and then back out again. It's setup as 24bit/44khz and very occasionally I'll get glitches as it hits peak CPU, esp on tracks where I'm using all of the above, so I'm looking for ways to reduce CPU load.

I've done a lot of optimising, e.g. reducing VST instrument voices, but it also occurred to me perhaps if I changed the setup to 16bit that might help.

But given the sporadic and random nature of the glitches it's hard to tell if it actually does help (average CPU level doesn't seem to be that different) and the fact that I didn't seem to get a glitch in the 16bit setup doesn't mean I wouldn't later – anyone know if it would actually make it any easier on the CPU, and therefore theoretically rarer glitches?

Also, anyone have an opinion on whether 16vs24 makes any practical difference in terms of sound output *specifically for live performance* of course.

Thanks!
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by Wonks »

Have you first done the normal checks like run a latency monitor to make sure there are no background tasks hogging the processor, no power saving schemes running, laptop (I'm assuming it is one) is sitting where it can be cooled properly and the CPU isn't slowing down because it's getting too hot through lack of ventilation paths and it's full of fluff inside?

Cubase will convert everything to 32-bit (or maybe 64 bit depending on the version) floating within Cubase itself, so the only real advantage of 16-bit comes from the latency side for getting information in and out of the audio interface, where obviously the data load is 2/3 of 24 bit. As the buffer will take longer to fill up, then the time between it being emptied (inputs)or filled up (outputs) will increase by 50%, which eases the load on the CPU, but it does increase the latency by 50% as well, if that is important to you for when playing software instruments.

Output sound wise, as long as the levels are reasonable, then you won't hear any difference at all through a PA, though you need to be a lot more careful on any audio input levels with 16-bits to avoid overloading. Maybe this is only vocals with your rig, so adding a compressor/limiter on those on the way in to avoid peaks might be sensible.

Are you using many reverbs, as they can be CPU intensive? You could try changing your reverb plug to see if you can find a more basic one that uses less CPU resource but still sounds OK for live use.
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by merlyn »

Wonks wrote: Fri Jan 28, 2022 1:19 pm Cubase will convert everything to 32-bit (or maybe 64 bit depending on the version) floating within Cubase itself, so the only real advantage of 16-bit comes from the latency side for getting information in and out of the audio interface, where obviously the data load is 2/3 of 24 bit. As the buffer will take longer to fill up, then the time between it being emptied (inputs)or filled up (outputs) will increase by 50%, which eases the load on the CPU, but it does increase the latency by 50% as well, if that is important to you for when playing software instruments.

16 bit doesn't affect latency. Try it. "As the buffer will take longer to fill up" -- how so? 16 bit reduces the bandwidth, but bandwidth is not a problem with audio. 2 channels of 44.1kHz 24 bit audio is a low amount of data as computers go.

Think about a buffer as say 64 slots that are filled with samples. At 44.1kHz there is 64/44100 = ~1.5ms available to calculate 64 sample values. If the computer manages that in the time available all is good, if it doesn't there is an xrun (glitch).
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by Wonks »

Yes, you are 100% right. My failing memory confused samples with bytes (or vice versa). I should have checked first.

So no latency effect.
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by BigRedX »

Try rendering all the VSTs that don't need to be manipulated by you in real time as audio tracks. That includes anything that is manipulated/automated by the computer as it plays.

Then do the same with any audio tracks that are being processed plug-ins that aren't actually being controlled by you in real time.
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by The Elf »

Using Cubase for a live performance is like taking an F1 car down to the corner shop for a carton of milk - sure, you can do it but...

I'd instead look to some performance software, which will make better use of your computer's resources and be more suited to the task. I use Cantabile, but there are others, depending on what platform you are on.
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by c_h_music »

Thanks for the suggestions everyone. Yes I've tried all the straightforward things like freezing VSTi's etc. reducing background processes, and changed reverbs only to be low CPU ones, and even increased buffer as far as I can and still be playable (about 20ms is almost ok). The 16bit thing was really just a last resort, but thanks Merlyn seems it's not worth pursuing.

Anyone know whether ASIO guard level, audio boost and disk preload settings in the Studio Setup box would make any difference *for performance*?

Elf, totally get your point about Cubase, and it's not really made for performance; but it's amazing when it comes to realtime routing changes, complex midi conversion, etc. and I haven't found a bit of performance software where I wouldn't have to spend absolutely ages recreating all the automation and modulation settings from scratch because they don't import correctly. One thing I love about Cubase is that I can go directly from a complex 100-track composition to a performance version of the same through a pretty straightforward process, and even easily undoing/redoing VSTi freezes later if I change my mind about what I want to perform live, or what I later feel needs to be improvised or what I want to control at performance time. Most performance software I've tried (I'm on a mac, so haven't tried Cantabile) would mean making too many hard decisions early on at export/import stage....

It actually works really well, it's just once every 20 or 30 songs it glitches. If my set is only 10 songs long I could easily do several sets in a row and never have an issue! But that one time it does is...... painful!
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Re: Live performance - 24bit vs 16bit in Cubase?

Post by BobTheDog »

I have found on a Mac anyway that buffer size has a huge impact on Cubase, could you go up a buffer size?
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