💾 Archived View for lofi.haiku-os.org › docs › develop › midi › midi1.gmi captured on 2024-03-21 at 15:02:07. Gemini links have been rewritten to link to archived content

-=-=-=-=-=-=-

How libmidi1 works

Midi1 is implemented on top of midi2, which means that libmidi.so depends on libmidi2.so to do the real work. BeOS versions earlier than R5 did not include a midi_server, because midi1 itself did not need it. (A server is only really useful if data must be shared between teams, something that midi1 did not allow.)

Midi2 is backwards compatible with midi1: The old libmidi.so still exists so that applications using the old API will run (providing binary compatibility). The old "BMidiPort" object is now a wrapper that uses the new "BMidiRoster" to allow connections to any published MIDI producer or consumer. Published MIDI objects are presented to the old MIDI apps as if they were physical MIDI ports.

Here is a very nice picture of how "BMidiPort" works:

[image: image0]

The softsynth

The General MIDI synthesizer is implemented in "BSoftSynth". This is a private class (not usable outside the API). It is not a real "BMidiEndpoint", so you will not see it appear on Patchbay. I did this for simplicity’s sake, for backwards compatibility (this is how the R5 synth worked too), and because we will have to give the Midi Kit a complete makeover for R2 anyway.

The "BMidiSynth" and "BSynth" classes delegate most of the work to "BSoftSynth". Not all of their methods are implemented, since some of them are very obscure. It would be a lot of work to figure out what they do, while it is likely that no applications use them anyway. However, "BMidiSynth" and "BSynth" should perform most common tasks without problems.

"BSamples" doesn’t do anything; its functions are mostly empty. In other words, with the OpenBeOS Midi Kit you cannot push waveform data into the output of the softsynth.

For simplicity’s sake, "BMidiSynthFile" is implemented using "BMidiStore", since the latter already knows how to parse Standard MIDI Files. Duplicating that functionality elsewhere would be pointless. However, this makes the behavior of our "BMidiSynthFile" a little different from what the BeBook says — as long as your applications are written properly, you shouldn’t notice any differences.