W3C home > Mailing lists > Public > public-audio@w3.org > July to September 2012

Re: MIDI Tracks and Sequences

From: James Ingram <j.ingram@netcologne.de>
Date: Mon, 17 Sep 2012 10:50:34 +0200
Message-ID: <5056E45A.9020409@netcologne.de>
To: Chris Wilson <cwilso@google.com>
CC: public-audio@w3.org, Jussi Kalliokoski <jussi.kalliokoski@gmail.com>, Joseph Berkovitz <joe@noteflight.com>
Hi Chris,

You said:
>  when delays are implemented you should be setting the msg.timestamp 
> in each message to += domhrtTimeAtStartOfPerformance.
immediately before the output.sendMIDIMessage(msg) call.

and -= domhrtTimeAtStartOfPerformance immediately afterwards (before the 
msgIndex++), otherwise the sequence gets corrupted for the next performance.

I've uploaded the correction as Test 8 [1] so that it doesn't get lost.

I've run test 8 twice.
Run 1: crashed after about 2 minutes with a deviation of 1563ms (!).
Run 2: ran to completion (timestamp 349800), exhibiting the same erratic 
behaviour as in test 7, and ending with the same repeating pattern. The 
last 4 deviations were 305, 255, 205, 155. Maximum deviation for the 
whole run was 313ms (at timestamp 345450).

>         Things like this is why we need native implementations of the
>         MIDI API.
>     Any chance of that happening in the near future?
> Well, obviously that's why I'm pushing this API along.  But I don't 
> have any announcement there; still looking for a webkit implementer.

Best of luck! :-)


[1] http://james-ingram.de/tests/JazzMIDIBridge/ji-known-sequence8.html

Received on Monday, 17 September 2012 08:51:21 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 19:03:11 UTC