Arch Linux

kokoko3k

Member

Registered: 2008-11-14

Posts: 2,461

Scarlett 2i2 1st gen weird latency issues, only at low samplerates.

Hi there,
I discovered that i have weird latency issues with that card.

By measuring it via jack_delay and a loopback cable, i noticed that the latency, for the same buffer size, is not always the same if i switch to another buffer size and back to it.

For example:
* Start jack
* set buffer size to 32 --> roundtrip latency: aroung 7ms.
* change the buffersize to 64 --> roundtrip latency around 13ms.
* change the latency back to 32 and, unexpected --> roundtrip around 10ms, not 7.

Going back and forward between 64 and 32 (or even other higher buffer sizes) dont give me consistent and expected results; the latency always fluctuates.

This problem seems to raise only for lower sample rates (44khz and 48khz); if i go up to 88khz or 96khz, the results I get are consistent and expected.
That said, i'd like to avoid higher sample rates because I don't really feel the need of that quality and I would like to keep the cpu load lower.

Right now, i'm supposing this is has something to do with the usb driver driving the card, because i tried to make a virtual loopback by connecting the output of jack_delay to his input (so bypassing any physical input/output ) and the latencies are consistent for every sample rate.

I've tried to play with snd-usb-audio "lowlatency" and "autoclock" parameters to no avail and i wonder if there is something i could try next.
There were a project named snd-usb-audio-lowlatency-dkms in the aur in the past with a lot of twekable parameters in the past, but now is gone.

Somebody has a suggestion?

Thank you.

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