Re: [Denemo-devel] MIDI out

[Jeremiah Benham]

On Mon, 2009-01-05 at 09:52 +0000, Richard Shann wrote:
> There has been some chat on freenode#denemo with Nils and others about
> what the MIDI out (that has so many votes in the denemo poll) actually
> means.
> For those not there and to summarize what I have understood here are
> some thoughts:
> 
> Just putting out a MIDI note to a libjack output connection in place of
> the playnotes which currently goes to the /dev/sequencer or to portaudio
> is not what is being talked about.
> 
> What is meant is (at a minimum) to be able to point to a place in the
> score and have denemo promptly start outputting MIDI to libjack. The
> MIDI events it would output would correspond to the notes from the
> pointed place onwards in the score, including the prevailing
> dynamic/crescendo, midi instrument/channel (anything else? - embedded
> MIDI commands I guess). Notes that are hanging on at the given point
> would not be sounded (so if the given point just contained notes tied
> from previous notes, nothing would be heard until a new note started).
> The tempo would be a prevailing tempo at the note concerned (so we would
> allow an embedded MIDI command that would change the tempo).
> 
> The actual jackmidi connection is trivial, of course, and someone on
> #denemo came up with a sample
> http://trac.jackaudio.org/browser/trunk/jack/example-clients/midiseq.c
> which shows how to do that.
> It is not intended that the user should be allowed to edit the score
> while it is being played. So the value of the gui->changecount variable
> is fixed for any given playback.

Would we have one output jack port for each staff or would we mash it
all into to one jack port?  If each staff is assigned a different port
(which I am assuming is what people want) when would the initialization
of that port take place? During staff creation time? It could not be
just before playback because the I assume the users would want to assign
the created jack ports to various soft synths. I guess I am just kind of
hung up here on the UI and where to implement it.

Would this feature be for this release or next? 

Jeremiah

> 
> What would require a little design is how to create the MIDI events from
> the denemo data. I think I have a good idea how to do this:
> An initialization stage would be good, partly to avoid excessive
> computation while playing & also for convenience of coding. So if this
> MIDI output system has not been initialized since the last edit to the
> score the first thing that happens is INITIALIZATION: this creates a
> list of MIDI events, with links from the notes in the score to first
> event that that note triggers. (As mentioned notes that are tied to
> earlier notes have no MIDI event).
> On requesting playback from a given note, the MIDI events are simply
> shovelled out to jackmidi.
> There are some extras that are easily incorporated - silencing staffs
> etc. but the real work is the INITIALIZATION task.
> 
> I think it can be done as follows:
>       INITIALIZATION: run a special version of exportmidi.c which instead of
> writing to a file creates a list (GList* midi_events in the DenemoScore
> structure) of MIDI events, putting a link from each note (etc) to the
> MIDI event which it causes.
> 
> To determine if INTIALIZATION is needed, we need to set a variable
> (gui->midichangecount) that is set to the gui->changecount when
> INITIALIZATION is run, so that if the comparison
> midichangecount==changecount fails when the play request is received we
> know INITIALIZATION is needed again.
> 
> As Nils noticed, exportmidi has at least one bug (dynamics) which I have
> put in the bug tracker.
> 
> I hope I have convinced someone that they could afford to devote an
> afternoon to implementing this.
> 
> Richard
> 
> 
> 
> 
> 
> 
> 
> 
> _______________________________________________
> Denemo-devel mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/denemo-devel