[Jack-Devel] How does --hwmon work?

David Kastrup dak at gnu.org
Sat May 6 20:58:30 CEST 2017

Ralf Mardorf <ralf.mardorf at alice-dsl.net> writes:

> On Sat, 06 May 2017 19:15:02 +0200, David Kastrup wrote:
>>But the cost for that at 3 bytes per note is just 1ms (more for
> No, when using external gear running status reduces it to 2 bytes, as
> long as just one MIDI channel is involved.

"at 3 bytes per note".  I know that there are situations where 2 bytes
are sufficient but you cannot depend on it.  But I'd expect chord
buttons to be able to use running status rather reliably.

> Simply use one MIDI interface, for each MIDI channel ;).

The Roland FR-1b does not even bother to use two connectors for input
and output.  They expect you to tell the Roland with a configuration
sequence when you want in- instead of output.  When you do, they
keyboard is dead (it will only accept notes via Midi then) until you
reconfigure or a SysEx dump is sent.  In the latter case, it will switch
the connector back to input, no questions asked.

I bought a single connector USB/Midi interface that will figure out
whether it is used for input/output on its own because I was not fond of
fiddling with plugs every time I want to work with SysEx.

> 1 ms as a fixed delay isn't an issue at all. I'm very sensitive to
> MIDI jitter, much more than it is expected from a "normal" human being
> :D. You should use alsa-midi-latency-test to check how much MIDI
> jitter you get. Very likely you get more than 1 ms of MIDI jitter.

So far I have not had any problems with the latency of sound production
using Aeolus.  Problem is rather when it deadlocks and keeps producing

David Kastrup

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