Latency Tip

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Kott
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Re: Latency Tip

Post by Kott »

Try the Arch kernel too - if anyone is reading this... worked better than every other distro for audio... on several systems .. this last year... for me.
What do you mean? Could you provide a comparison?
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Toejam76
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Re: Latency Tip

Post by Toejam76 »

There is a lot of good information here. One thing that I am still wondering about is, how does the USB interface relate to DSP load. For example, one a single track with bunch of demanding plugins Carla shows high DSP load while the "Performance Meter" in Reaper shows around 15% RT load at the same time. So i was wondering if another USB interface could help with that or if the CPU is limiting.The interface is a Focusrite Solo 2nd gen and the CPU a Ryzen 5 3400g with 3200 mhz DDR4.
I've read somewhere, can't remember where, that on the Focusrite 2nd gen devices the DSP does the heavy lifting and on 3rd gen device the CPU (loosely paraphrasing here). So I was thinking about getting a better interface like an Audient44 to run more plugins at the same time, but I am just not sure if that would solve the problem of high DSP load or if I need a faster CPU like a new AMD APU (don't need a seperate graphic card). If someone has some info on that, I'd greatly appreciate it.
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Linuxmusician01
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Re: Latency Tip

Post by Linuxmusician01 »

Toejam76 wrote: Sun Nov 14, 2021 8:04 am There is a lot of good information here. One thing that I am still wondering about is, how does the USB interface relate to DSP load. For example, one a single track with bunch of demanding plugins Carla shows high DSP load while the "Performance Meter" in Reaper shows around 15% RT load at the same time. So i was wondering if another USB interface could help with that or if the CPU is limiting.The interface is a Focusrite Solo 2nd gen and the CPU a Ryzen 5 3400g with 3200 mhz DDR4.
I've read somewhere, can't remember where, that on the Focusrite 2nd gen devices the DSP does the heavy lifting and on 3rd gen device the CPU (loosely paraphrasing here). So I was thinking about getting a better interface like an Audient44 to run more plugins at the same time, but I am just not sure if that would solve the problem of high DSP load or if I need a faster CPU like a new AMD APU (don't need a seperate graphic card). If someone has some info on that, I'd greatly appreciate it.
I didn't read the whole topic, sorry.

But about (USB) audio devices. If I'n not mistaken Focusrite audio devices require a (reverse engineered?) driver in Linux. I don't think that will cause latency and/or Xruns but it might: you never know. If you want to experiment with getting less latency/xruns and audio devices you might try a "driverless" out of the box working audio device like the U-Phoria ones from Behringer (link example of one at Thomann). Most say they're not bad for the money (Midas pre-amps, whatever that may mean) and for comparison of xruns/dsp load ideal I think.
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Toejam76
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Re: Latency Tip

Post by Toejam76 »

@Linuxmusician01
I don't have problems with latency or xruns. It's just as good as on Windows or Mac, but I wanted to know if I could get better performance with a new interface or rather get a new CPU (APU), because DSP load is on the edge according to Carla with a few "big" plugins like Arturia or Kontakt stuff.
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Re: Latency Tip

Post by merlyn »

Toejam76 wrote: Sun Nov 14, 2021 8:04 am One thing that I am still wondering about is, how does the USB interface relate to DSP load.
I would have thought it doesn't. What's called an 'interface' these days is really a 'studio in a box'. I f we think what an interface is -- it has an analogue input and a digital output that a computer understands.

Guitar > A/D convertors > USB > Software

All the other features, like mic pre-amps and direct monitoring used to be separate boxes.

So really an interface is quite simple. All USB interfaces on Linux use the same driver -- snd-usb-audio -- so there shouldn't be a lot of difference between different models and brands. As with everything it has to be tested before a definitive statement can be made, and in practice there may be some variation. But as far as the idea that improved audio performance is something that can be bought by upgrading an interface -- I think that's a fiction convenient for manufacturers who want to sell interfaces to slack jawed consumers a.k.a. Windows users :) Parallax scrolling websites showing guitar playing hipsters plugged into the latest hardware sell interfaces; they might not be so good from a technical information point of view.

Other opinions, and particularly data welcome.
For example, one a single track with bunch of demanding plugins Carla shows high DSP load while the "Performance Meter" in Reaper shows around 15% RT load at the same time.
I haven't used Reaper much, so I haven't experienced that. Could it be single/multi thread? As far as I know Kontakt is single threaded, so it could use up a single core before the whole processor is maxed out. From what you say there appears to be some difference between how Reaper and Carla define DSP load.
I've read somewhere, can't remember where, that on the Focusrite 2nd gen devices the DSP does the heavy lifting and on 3rd gen device the CPU (loosely paraphrasing here).
I don't think that's the case. Take e.g. an RME card that has DSP built in -- it can only process the signals on the card. If a USB interface did do some of the DSP audio data would have to be sent back and forward between the computer and the interface, increasing latency, which I'm fairly sure is not happening. Again, anyone with evidence to the contrary please post.
The ultimate hidden truth of the world is that we make it, and could just as easily make it differently.
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Toejam76
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Re: Latency Tip

Post by Toejam76 »

If a USB interface did do some of the DSP audio data would have to be sent back and forward between the computer and the interface, increasing latency,
That's a good point and makes total sense. I was thinking that the USB DSPs are doing something similar like those internal DSP cards.
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