[Jack-Devel] Focusrite Scarlett USB interfaces: 48000 preferred over 44100?

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[Jack-Devel] Focusrite Scarlett USB interfaces: 48000 preferred over 44100?

Holger Marzen
Hi all,

I have several Focusrite Scarlett USB interfaces:
- Solo
- 2i2
- 2i4

They work out of the box but I noticed some flaw in either their
firmware or ALSA or jackd:

- with 48000 I can use much lower buffer sizes (down to 32) as with
  44100 (at least 96)

- with 44100 I have some slight clicks, about one per minute, sometimes
  less. Those clicks sound as if an electrical device (refrigerator,
  lights) was switched on.

- with 48000 I have no such clicks.

Has anyone made the same experiences? With Scarletts? With other
USB-Interfaces? Is jackd or ALSA optimized for multiples of 48000
instead of 44100?

Regards
Holger
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Re: Focusrite Scarlett USB interfaces: 48000 preferred over 44100?

Ralf Mardorf
Did you test all available USB ports of your computer?

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Re: Focusrite Scarlett USB interfaces: 48000 preferred over 44100?

Holger Marzen
On Sun, 23 Sep 2018, Ralf Mardorf wrote:

> Did you test all available USB ports of your computer?

Yes. And several computers with different kernels.
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Re: Focusrite Scarlett USB interfaces: 48000 preferred over 44100?

Robin Gareus
In reply to this post by Holger Marzen
On 09/23/2018 07:14 PM, Holger Marzen wrote:

> Has anyone made the same experiences? With Scarletts? With other
> USB-Interfaces? Is jackd or ALSA optimized for multiples of 48000
> instead of 44100?

This applies to all USB1/2 class-compliant devices.

USB framing itself prefers 1ms boundaries (or USB2 micro-frames
125usec). See https://www.linuxmusicians.com/viewtopic.php?t=10707

There was a good in-depth explanation about this a few years ago on
either the LAD or LAU email-lists. If I remember correctly by Clemens
Ladisch, but I can't find it just now.

Cheers!
robin

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