[LAU] How to get a persistent midi instrument source port? ( lightweight )

Len Ovens len at ovenwerks.net
Sun Mar 24 15:55:41 CET 2019

On Sun, 24 Mar 2019, hgn wrote:

> In case the JACK devs are reading:

Not a jack dev ... but

> AFAIK Jack works under the assumption that audio System out 1 and 2 are 
> the main abstracted stereo outputs and are available on any system. This 
> leads to great portability across all systems.

I think you will find that rather than jack assuming anything, it is the 
various jack clients that assume system 1 and 2 are stereo left and right. 
As this is not always the case, allowing the user to not auto connect is a 
good idea. Concider many devices have different outputs for line and 
headphones and aes3/spdif ports are almost never 1 and 2. However, for 
most users, 1 and 2 are a good guess.

> I consider midi data entry with a single instrument an equally typical 
> use case and would like to propose to add a single midi thru port to 
> JACK directly. No more, no less, nothing to configure, nothing to check 
> for as user or developer.

If you are using jack MIDI with ALSA then you would normally be using 
a2amidid (at least in jack2) which already shows the default alsa MIDI 
through set of ports. As jack1 comes with a2jmidid included, I would 
assume the right commandline parameters would import the system through 
port there as well. On my system, the MIDI portion of jack_lsp shows:
a2j:Midi Through [14] (capture): Midi Through Port-0
a2j:Midi Through [14] (playback): Midi Through Port-0
a2j:Ensoniq AudioPCI [16] (capture): ES1370
a2j:Ensoniq AudioPCI [16] (playback): ES1370

Len Ovens

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