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Re: MIDI Tracks and Sequences

From: Chris Wilson <cwilso@google.com>
Date: Mon, 10 Sep 2012 15:48:54 -0700
Message-ID: <CAJK2wqUR3TBOg00c9M+ptAhLaJxNoCO==H0B1eaBGNn8X_t7sA@mail.gmail.com>
To: James Ingram <j.ingram@netcologne.de>
Cc: Jussi Kalliokoski <jussi.kalliokoski@gmail.com>, public-audio@w3.org
Hey James -

A while ago, I poked at implementing Standard MIDI File reading in
Javascript (https://github.com/cwilso/Standard-MIDI-File-reader), and my
conclusion was basically that it would be best provided as a library and/or
as baked into the standard <audio> player engine in the browser, rather
than centering the MIDI API on it.  There are a lot of challenges with
doing rewinding, for example, and seeking.  There is also a lot of dynamic
control hooking in to tempo changes, live information exposure of events,
etc., that any "serious" sequencer would probably want to have.  Even in
that relatively naive reader, there are a bunch of different types of data
- it has more exposure than the MIDI API does by itself.  Once we've got
the MIDI API locked down and implemented, I'll probably go back and flesh
out my SMF reader as a library for reading and playing SMFs, and we can
talk about if it's a useful v2 standard library.


On Mon, Sep 10, 2012 at 5:06 AM, James Ingram <j.ingram@netcologne.de>wrote:

>  Hi Jussi,
> I think support for Sequences would be useful (and easy to provide), even
> if we are not talking about file output.
> Loading sequences from files is very common in MIDI programs, and I see no
> reason why that should not be done on the web. So it would be nice to have
> a standard Sequence definition with which to work. I'm not saying that
> Sequences necessarily have to be loaded from SMFs, but if the Sequence
> definition existed, it could obviously be given a loadFromSMF(url) member
> function.
> Also, if we had a Sequence object, it would wrap the output device, and
> play(), stop(), rewind() etc. functions could be provided quite cheaply out
> of the box. That might make Web MIDI even more attractive. :-)
> But maybe I'm too close to the problem. Is there anyone else out there who
> needs to send a Sequence to the output device?
> best,
> James
>  Hi James,
> A side note: the current spec has the notion of MIDIEvent as a DOM event
> that occurs when MIDIMessage(s) are received.
> The toolkit you're referring to deals both with MIDI files (SMF) and MIDI
> devices. Our API is designed to work with just devices, and MIDI devices
> are just I/O, there's no notion of high level concepts such as tracks
> (although there's channels, but that's already in the spec) or sequences,
> unlike SMF does. It would seem a bit weird to me to complicate the spec
> with such high-level concepts as we don't even support reading / writing
> SMF files, nor do I think we should as the intent of the device is
> explicitly to allow communication with MIDI devices.
> Cheers,
> Jussi
> On Mon, Sep 10, 2012 at 12:32 PM, James Ingram <j.ingram@netcologne.de>wrote:
>> Hi Chris, all,
>> Chris Wilson said (apropos Bug 18764)
>>> I'd like to explicitly ask for MORE feedback from developers
>>> using MIDI today on this issue.
>> I'm following the Bug 18764 debate very closely, but don't have the
>> in-depth knowledge of MIDI's finer points to contribute much to the
>> subject.  All I want as a future user of this API is that it is going to be
>> succinct, work as efficiently as possible and be clearly documented.
>> Whether functions are overloaded or not is not really crucial. If I want to
>> use the Web MIDI API, then I'm going to have to learn it one way or the
>> other.
>> But I'd like to open another can of worms: :-)
>> The current version of the API [1] supports MIDIMessages and MIDIEvents.
>> Would it be possible for it to provide Sequence and Track objects as well?
>> I've written my own versions of these for my current project (in
>> Javascript), but think there must be people out there who know much better
>> how to write them than I do. They are prime targets for optimization. We
>> should not all have to re-invent the wheel.
>> Interestingly, there are versions of these objects in Leslie Sanford's
>> popular C# MIDI Toolkit [2]., so he also seems to have thought that they
>> were worth providing.
>> Any thoughts?
>> Best,
>> James
>> [1]
>> https://dvcs.w3.org/hg/audio/raw-file/tip/midi/specification.html#callback-navigatormidiaccesssuccesscallback-parameters
>> [2] http://www.codeproject.com/Articles/6228/C-MIDI-Toolkit
> -- www.james-ingram-act-two.de
Received on Monday, 10 September 2012 22:49:24 UTC

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