General latency questions

hi. if im not using a realtime kernel, ie with raspberry pi os, is it possible that latency could shift around, introducing tempo drift? or does it generally stay at the same latency once its set?

im definitely willing to install patchbox to test but if theres someone with this knowledge can you please set my mind at ease before i do that? im trying to identify the source of my tempo drift.


Do you mean you are experiencing tempo drift with your current system? With the fact that I’m just a hobbyist, I don’t think I have ever experienced any drifting latencies with windows/macos (non-real time) systems. it stayed 20ms, 8ms, or whatever depending on configuration but without changing preferences I felt no changes.
I think latency fluctuation occurs in non realtime OS is in few CPU cycle range -which is few microseconds- and non-perceptible for human

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yeah my rpi4b and 5 running audio apps seem to have latency that either jumps around or drifts. this is without patchbox.

when i say tempo drift that characterization is inaccurate. im not sending midi clock to my rpi5, im only sending midi note commands. i am sending midi clock to a polyend tracker and this contrasted with audio from the rpi5 make it sound like there is drift related to midi clock when its actually the latency of the rpi5 moving around.

and it works on the raspberry pi 5! nice!

so i still seem to be getting 30ms latency with the kernel that boots by default… is this the realtime kernel, or will i need to switch to it to get the lowest latency? is there something that describes this? thanks

See the Kernel section here: [Beta] Patchbox OS Bookworm ARM64 2024-04-04

What latency are you measuring?

without switching to the rt kernel, 30ms seems to be my latency. ill post again after trying the rt

where is this menu: patchboxkernel

i cant seem to find it

Run the command patchbox in a terminal, it should be there, if not, send us a screenshot.

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i thought i did that but maybe i messed it up somehow. ill be back with the results later. thanks

typo i guess. so this is awesome! does the setting stick once you set it?

edit: noo it seems to not like the rt kernel. it doesnt seem to boot. black screen. Pi4B 4GB, sandisk usb 3.2 boot drive, hifimediy sabre sound device

Try using the regular booting method from the SD card directly.

so dont use the faster usb 3.2 drive to boot from? ok ill use the sd to see if it works better.