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Hi there,
I was drawn to arch because of this page here https://wiki.archlinux.org/index.php/Pr … E_Babyface which promises quite low latency (which I need for Jack software monitoring), but only if "Latencies of 5ms down to even as low as 1ms can be achieved with good hardware and proper configuration."
Since I already have experiences with PREEMPT kernel and Jack setup http://jackaudio.org/faq/linux_rt_config.html, my questions are:
- is there some more "proper" configuration to achieve the low latency which am I maybe missing?
- what is meant by "good hardware"? (given that I already have the audio interface, are there any recommendation for the rest?)
Best regards,
Marek
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To answer my own question, for future readers...
From https://forum.rme-audio.de/viewtopic.ph … 76#p203276:
I'm running the original Babyface (USB ID 0424:3fb7 ) for around 9+ years in CC mode under Linux (either Debian or Ubuntu) with a low-latency kernel (currently 6.2.0-1003-lowlatency ) through a Renesas uPD720201 controller PCIe expansion card (into which I do not connect any other devices), with its original USB cable (yes, the cable matters), no JACK just ALSA, and am getting 3,85 ms RTL measured in Ardour at 48 kHz, 32 samples / 3 periods, without sound artifacts like cracks, pops, buzzes, etc.
To supplement the above:
More about sample rate, sample buffer size and buffer period setting here https://wiki.linuxaudio.org/wiki/list_o … _interface
Relevant lspci excerpt:
03:00.0 USB controller: Renesas Technology Corp. uPD720201 USB 3.0 Host Controller (rev 03)
User running Ardour with ALSA audio system, or JACK has to be in group "audio",
for JACK set in /etc/security/limits.d/audio.conf
@audio - rtprio 95
@audio - memlock unlimited
More on this at https://jackaudio.org/faq/linux_rt_config.html, but using JACK is not a requirement.
Tested in Ubuntu 23.04, further suggestions to achieve lowest possible round-trip-latency:
- USB controller does matter a lot, I've tested with Renesas uPD720201, but uPD720202 may work similarly
- if the latency is not low enough one may experiment with PCIe card placement, as the actual slot may matter (that is through MB's chipset or not)
- don't use USB hubs or repeaters, quality extension cables may be okay
- if using bus-powered interface like RME Babyface or Babyface Pro (FS), provide the audio interface additional power using a DC power supply
Last edited by cupakm (2023-06-04 05:32:57)
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This setup generally does help with any other USB audio interface, I've tried also some low-cost ones like ESI U24XL, which performed around 7 ms RTL with same settings.
Last edited by cupakm (2023-06-04 05:38:14)
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