USB latency, measurements, effect of HUB

[mprinz]

Hi freaks,

I pulled this doc up from a Google search.

Since I plugged more and more MIDI controller into the hub where my edrumins are connected to ... actually with second hub, I was again asking myself...What about the stupid latency?

And I found this work from german university students:

https://epub.uni-regensburg.de/40182/1/ ... ersion.pdf

For me the important info is below 6.3:
The hub has no effect on latency.
But they only plugged in a single device.
Anyway, see, only the gamepads and controllers have a low latency.

With regard to the section 6.2 Forced 1000 Hz polling rate I would like to ask Rob, what rate is desired by the edrumin devices.
Oh may I check that in the windows device manager?

It would be interesting to see those measurements from USB MIDI devices like drum modules, controllers etc.

With regard to computer audio and USB MIDI latency, I would like to recommend this video again:

https://youtu.be/7QtTfR9VSa8

I think, we can be sure not having USB latency issues.
I mean, the Xtalk cancelation is working via USB. So,
the data from the ext. device has to be there and processed, before a note is generated or not.

Greetings

Manuel

[Rob]

I don't have much to say on the matter except that xtalk cancellation works with external MIDI devices because the speed of USB MIDI packets far exceeds the speed of mechanical vibrations that cause xtalk issues.

Hub, routers, switches and like are sharing information at close to the speed of light. Think about how many different pieces of hardware internet traffic has to pass though, yet I can video chat with a person on the other side of the planet with no perceived latency.

[mprinz]

Hi Rob, basically I agree with that.
But you know it better than me. The problems may occur due to the digital processing or protocols or as I mentioned - polling rates.

In this article... when they set the polling rate higher than the default values, some devices revealed a lower latency.

I was thinking... hmmm...if every hub may add a 1 ms due to the polling rate of 1000 Hz or lower ...

I am not a USB geek, I guess it's per cycle on the whole bus.
Anyway, as you said, now I would state, latency issues are NOT due to USB connections.

Mainly scan time + audio buffer of the interface.

Greetings

Manuel

[mprinz]

Do the eDrumIns use USB 2.0 or 3.0...

[mprinz]

Ok, if anyone is still interested in:

I copied a few GByte back and forth over the following
USB wiring:

PC root hub ---> active 5m extension ---> 7 port (2x eDRUMin4, 1x eDRUMin10, sample pad, MIDI foot controller) ---> another hub (3x Korg nanoKONTROL2 and the SDcard reader. All components are labeled to be USB 3.0 conform.

There was no noticeable longer latency when playing the edrums during the file copy processes.