Typical latency with USB interfaces?

I’m using a Focusrite Scarlett 6i6 (1st Gen) on a Thinkpad X250 Laptop. What latency do you achieve when using similar hardware with Linux?

I measured my latency as 16ms (using jack_iodelay, connecting in1 to out1 on the audio interface). However, only 5.33ms come from “inside” jack as it seems (48 KHz/128 Samples/2 Buffers = 5.33ms). Is this result plausible?

Yes it’s plausible. It’s the roundtrip latency, your converters need a bit of time to process the incoming and outcoming audio. It means that your interface needs roughly 5 ms to DA and 5 ms to AD and jackd adds 5 ms to it. It’s a bit on the high side but it’s plausible. And no, you can’t lower your hardware latency (well maybe with a firmware update), just jackd latency.

Thanks for your reply. Are these also typical latencies when using windows?

Hi, Focusrite Scarlett 18i20 (1st Gen) user here. I get more or less the same results than you. However, I usually run it with 3 buffers. With a proper system configuration, you could go to 48kHz/64/3, if not using lots of synths, but only some EQ and compression.

As @Upacesky has said, there are other stuff involved in the roundtrip latency. However, AD/DA converts aren’t so slower. I mean, they do not take 5 ms. I recently discovered that Linux kernel adds an internal buffer(s) when using USB devices, so that’s why roundtrip latency is bigger. There is a good explanation and diagram here about what’s going on with roundtrip latency:

If you use JACK 2 (1.9.xx) with default async mode (no --sync option), there is one cycle extra latency: The nominal round-trip latency is 128 * (2 + 1) / 48 kHz = 8.0 ms

Either way a total of 16ms is not unrealistic.

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