[LAU] MIDI over USB

[Robin Gareus]

On 06/01/2018 11:45 PM, Will Godfrey wrote:
> On Fri, 1 Jun 2018 22:50:50 +0200
> Robin Gareus <robin at gareus.org> wrote:
> 
>> On 06/01/2018 09:00 PM, Will Godfrey wrote:
>>> Something just occurred to me.
>>>
>>> Does anyone know if this is transmitted any faster if going computer to computer
>>> rather than between hardware devices. So do you get lower latency?  
>>
>> You have more bandwidth but not usually lower latency.
>>
>>> Also what about keyboards that work entirely as MIDI over USB connecting to a
>>> computer?  
>>
>> Depends on the keyboard.
>>
>> It seems that may chipsets still use the 31.25kbaud (probably because
>> you can get USB to physical MIDI ASIC cheap off the shelf).
>>
>> You can check with jack_midi_dump (or similar). Elbow press/release
>> 30-40 notes on a keyboard and check if most individual note events are
>> spaced less than 1ms apart. If they are, then the interface is faster
>> than physical MIDI.
>>
>> ciao,
>> robin
> 
> Now why didn't I think of that?
> Thanks Robin :)
> 

I just tested with a M-Audio Oxygen 49 (which only has USB MIDI)

I've used an A4-book to press/release 14 white keys, recorded it with
Ardour. The 14 note-off events span 220 samples (@48kHz, ~4.5ms).

So the device has a higher bandwidth than physical MIDI (approx 3
times). I can't say anything about the latency though.

All other devices that I have here do have an physical MIDI port (5pin
DIN) and are only 31.25 kbaud have ~2.0ms round-trip latency.

Cheers!
robin

PS. note-on events are spread out further because I didn't manage to
press the book (or elbow) down accurately enough.