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Re: [Denemo-devel] Denemo and Jack


From: Richard Shann
Subject: Re: [Denemo-devel] Denemo and Jack
Date: Sun, 17 May 2009 11:47:12 +0100

Now I have looked into the code - it seems that everyone using JACK with
MIDI input will be activating the code which calls portaudio output
routines to emit a (denemo synthesized) note for each MIDI key pressed.
This will happen regardless of the setting of prefs->playback
immediately.
On my machine, I actually hear these notes. There is no other code to
output single notes  - nothing has been written to output a single note
via JACK, only an entire MIDI file (used when playback is invoked).

Can anyone who is using JACK midi in say whether they hear synthesized
sine wave pitches played on entering notes (the same as are heard when
the Input->MIDI input has *not* been checked and notes are being entered
from the pckeyboard)?

It will be good to output MIDI notes via JACK rather than synthetic
ones: It seems that the fundamental bit of code looks like this

                                buffer = jack_midi_event_reserve(port_buf, i, 
3);
                                buffer[2] = 64;         /* velocity */
                                buffer[1] = note_frqs[j];
                                buffer[0] = 0x90;       /* note on */

(taken from the examples). Jeremiah - were you planning to do something
like this?

'''
> This assumes all JACK preferences are unticked
> ie 
> start denemo Edit->preferences
>       * Not Enable Jack Transport starts
>       * Not Jack Transport starts stopped 
>       * Not Enable jack at startup 
>       * exit denemo
>       * 
I should have also mentioned the once-only setup in qjackctl of setting
Setup->Midi Driver->"seq" rather than "none" which was set initially.

Richard





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