Crackling input on rpi 4

[comaticscale]

Dear All,

I´m running Reaper on a raspberry pi 4 with hifiberry digi+ i/o under raspbian buster. The configuration is pretty simple: I have linux sampler running with a piano sound and an instance of Reaverberate. Sample size is set to 64 which is as low as I have to go in order to achieve decent latency (which I believe is more than what´s reported by Reaper), and I do get a pop and crackle now and then which however does not bother me too much.
My big issue is when I open up for the input on the hifiberry card on a new track. The signal crackles like crazy, without me doing nothing but having reaper open, and not even playing on my keyboard through linux sampler.
So I was wondering if anybody know any tricks to get rid of this problem, without touching the latency buffer settings. In my opinion, there shouldn´t be much cpu overhead involved in simply forwarding input to output here, but of course I may be wrong.
The goal is to have another raspberry (with a hifiberry digi+) output its audio signal, which contains the sounds coming from youtube, spotify etc. and then hear it through the pi with Reaper on it, so that I can both do my normal stuff, and always be able to play on my keyboard through linux sampler without having to fiddle with things first.
I hope I´ve made myself clear, if not let me know.

Thanks in advance!

[Glennbo]

What if you add one more period, but keep the 64 sample buffer?

The other thing you might look at is the performance guide for Raspberry Pi and Pianoteq. This is for a Pi3 but the performance tweaks towards the end should still be valid if you have a Pi4.

https://www.pianoteq.com/download?fi...yPi3_v3.pdf%20

[timothys_monster]

Have you tried turning up the RT priority in the audio device settings? What driver are you using? ALSA?

Does it still crackle on 128 samples? Where are you sending the signal to anyway? The Hifiberry that you are using only has digital outputs as far as I recall.

[comaticscale]

Thanks guys, it actually helped increasing the periods to 5 while still on a buffersize of 64. The output goes to another raspberry with kodi/libreelec, that´s got a hifiberry DSP board in it. This one´s connected to my main amplifier, ensuring that everything is always playing what I want without changing the input on the amplifier, and there are times where it´s cool playing along on my midi keyboard to something playing on the "desktop" pi. I could have purchased a mixer for the same, but I doubt it´d be cheap when the requirement is 3 optical inputs.
I´m using ALSA and RT is set to 99. I´ll check the pianoteq guide, should I need further tweaks.

[Jack Winter]

FWIW, you probably shouldn't use a priority of 99 as that's normally reserved for a few house keeping threads, 98 should be ok though.

[comaticscale]

Originally Posted by Jack Winter

FWIW, you probably shouldn't use a priority of 99 as that's normally reserved for a few house keeping threads, 98 should be ok though.

Thank you Jack, will change it!