On 7/18/20 8:28 PM, Iain Mott wrote:
Hi list, I have a Focusrite Scarlett 3rd Gen interface that is producing audio glitches with a Raspberry Pi 4 running a realtime kernel (or not). I had similar problems on a laptop and on a desktop. On the laptop however it now runs perfectly with the very latest Linux Mint and the standard kernel. On my desktop I get acceptable results with AV Linux although haven't tried it with the latest Mint. There are no error messages reported or overruns, just glitches which are independent of buffer sizes and sample rates.
Hi, on a rpi 4 and with a "RT-PREEMPT-FULL y" kernel you also want to change the IRQ thread priority of the xhci (usb host controller). I think it's always on the same irq line (at least it's for me on two different rpi4s). This should do the trick: schedtool -F -p 90 $(pidof irq/38-xhci_hcd) This seems to make the audio processing on my rpi4 *much* more robust to SD-card accesses. Before my daily borgbackup job at 6am caused a storm of xruns. Now none at all anymore. You mentioned no xruns reported by the software so in principle this _should_ have no effect. Possibly the software xrun reporting is broken though, so give it a shot. Also make sure that you run your audio processing threads with a realtie priority higher than 50 (the default priority for irq handler threads in the kernel). With jack I'd recommend running it with jackd -R -P 80 ... Regards, FPS -- https://fps.io _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx https://lists.linuxaudio.org/listinfo/linux-audio-user
