Hm, the audio latency doesn't fluctuate so it's not like the testing conditions affect the measurement. The audio latency is a fixed quantity that depends completely on the number of storage elements in the data path which isn't variable.

Perhaps the better thing to focus on is the frequency of underruns (or "xruns" as they say on Linux, which also covers overruns) for a specific sample rate and buffer size setting. The histograms on my page (which should be animated BTW) show real time processing latency measurements while running the audio all the way through Bitwig with a moderate DSP load (multiple instances of Pianoteq, samplers, live MIDI input). On my system (details at the bottom of my page), I can do this at 48 kHz and 64 sample buffers with zero underruns. If I drop down to 32 samples per buffer, I do start getting underruns.

All I can do from the hardware side is try to minimize the processing latency of a typical cycle so that there is head room to absorb jitter. The vast majority of the jitter comes from the Linux host. It's up to the end user to tune the system for low jitter. This is usually the case for audio on Linux, and the rabbit hole can go pretty deep on system tuning.

Just curious though, since I don’t work at these sample rates. Is resampling not good enough? Or maybe I don’t understand the mastering flow.

One way audio latency is about 3.6 ms divided by two = 1.8 ms. This type of latency is audible.

Processing latency is just the amount of time it takes to complete all processing for each audio cycle. From the histograms, the typical processing latency is about 625 us and of course there is some jitter (almost all of the jitter comes from the Linux host BTW). Processing latency is not audible. However if the processing latency exceeds the deadline on a given audio cycle, there will be an underrun which will cause an audible glitch.

https://interfacinglinux.com/linux-compatible-audio-interfac...

AFAIK the best one is RME AIO Pro PCIe card. ETH-68 matches the round trip audio latency of this card at 48 kHz and surpasses it be 0.33 ms at 96 kHz.

I have my eye on some other codecs for the next project.