[gst-devel] Re: potential for midi support in GStreamer

[Jonas Birmé]

mån 2002-06-17 klockan 16.10 skrev Baker, Steve:
> I've thought a bit about how to add midi support to GStreamer. I'm just
> going to do a brain dump of my ideas since I doubt I'll be coding any of
> this any time soon.
> 
> Midi could be thought of in terms of dataflow as a sparse non-constant flow
> of bytes. GStreamer works best with near-constant data flow so a midi stream
> would probably have to consist mostly of filler events, sent at a constant
> tick-rate.
> 
> I think the following 3 elements would be most useful initially:
> - midifileparse
> takes midi file format data on sink pad, and produces timestamped midi data
> on output. A property will specify what the tick rate would be (default to
> 96 ticks per beat or something). If no data exists for a given tick, it can
> just send a filler event. Timestamp would be derived from the bpm property,
> and the time deltas of the midi file data.
> 
I think I will begin with this. A 96 PPQN as default sound good, what
about multitrack midifiles? (type > 0)
Should it be a pad for each track?
Maybe multiple pipelines, one for each track?
Sounds like a neat thing to do? Splitting it up in several sequences,
the word dynamic come to my mind.
But maybe at first, limit myself to SMF0 (Midi Format 0), i.e. only one
track.
Anyone has any midi files of that format?

> - ossmidisink
> could be added to the existing oss plugin dir, sends midi data to oss midi
> sequencer. Makes extensive use of GstClock to only send out data when the
> buffer/event timestamp says it should.
> 
> - alsamidisink
> guess what this does. don't know whether alsa's sequencer interface would be
> better than its raw midi one. My money is on raw midi.
> 
> - ossmidisrc, alsamidisrc
> real time midi input.
> 
> It would be nice to be able to transform midi to audio which can be further
> processed in a gstreamer pipeline. Timidity might be the best hope for this,
> but I don't think they have any intention of libifying it, so any timidity
> plugin would have to communicate with Timidity in some out-of-process way.
> Hadess claims that there is a librarified version of Timidity out there, but
> I have never looked for it.
> 
> Once we have midi streams, we can start doing fun things like writing a
> midi2dparams element which would map midi data to control the dynamic
> parameters of other elements, but lets not get ahead of ourselves.
> 
> cheers
-- 
Jonas Birmé (jonas at birme.se)           ICQ: 12030785
http://home.birme.se/~birme/           IRC: birme at GIMPNET
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