How to schedule?

[cristianvogel]

Hello!

Many thanks for maintaining this excellent library. It is clear, well documented and easy to use.
I am working to add a midi out feature to an app written by someone else which originally sequences sample based audio buffers with a complicated promise based system.

I am trying to inject WebMidi in there.

I have succeeded more or less, but wondered if I would get tighter MIDI events, by scheduling them in a similar way to the original code does with audio. I think the original code uses a scheduling list, which I believe WebMidi is capable of for notes.

But I don't really understand how to do this when my relative reference is another timer, not WebMidi.time

WebMidi.outputs[0].channels[1].playNote("C3", {time: WebMidi.time + 3000}); WebMidi.outputs[0].channels[1].playNote("C3", {time: "+2000"});

The code base I am working on his here Twotone
and I try to inject the WebMidi note out here

The original author of this program has retired from this project and is unavailable, so I'm trying my best to understand how to add a Midi Out feature into a complicated system of callbacks

[djipco]

I'm not quite clear on what you are asking. One thing that is for sure is that WEBMIDI.js can connect to existing input and output ports but cannot create new ports.

By the way, WebMidi.time is simply an alias to performance.now().

[cristianvogel]

Thanks for your answer. Focussing on the WebMidi.time question. In the codebase I am working with, it seems that a performance timer starts when the user presses play, like as if performance.now() could be rest to 0? I guess I am asking how I can make relative scheduling of WebMidi notes against a different highres timer than performance.now which I think is not resettable? Or is it?

[djipco]

You cannot reset performance.now(). However, what you can do is save the offset between the moment you press "play" in your system and WebMidi.time. Then, whenever you want to schedule a note, you just have to add this offset.

This got me thinking though... perhaps this could be added to the library. It wouldn't be hard to implement what I wrote above into the lib so that WebMidi.time can be reset. I'll add that to my list of things to evaluate.

[cristianvogel]

I think thats a good idea. I found this guide by @haszari which might make this feature addition straightforward for you.

https://github.com/haszari/sync-web-audio-web-midi

[djipco]

Awesome! Thanks for the link. It makes total sense to find a sensible way to sync WebMidi.time with an external source (such as Web Audio or others).

[haszari]

Coolness! 🙌