(CircularRouting): Undefined behavior for circular graphs

[olivierthereaux]

Originally reported on W3C Bugzilla ISSUE-17326 Tue, 05 Jun 2012 11:18:29 GMT
Reported by Philip Jägenstedt
Assigned to

Audio-ISSUE-24 (CircularRouting): Undefined behavior for circular graphs [Web Audio API]

http://www.w3.org/2011/audio/track/issues/24

Raised by: Philip Jägenstedt
On product: Web Audio API

The spec does not define whether or not circular connections are allowed. Whichever is the case, the behavior needs to be defined.

[olivierthereaux]

Original comment by Olivier Thereaux on W3C Bugzilla. Thu, 07 Jun 2012 16:07:25 GMT

Proposed changeset, 25 May 2012
https://dvcs.w3.org/hg/audio/rev/74bd0f9f2fb6

Resolution per http://www.w3.org/2012/05/30-audio-minutes.html#item02
«it is OK to have a circular graph so long as there is a delay. The minimum delay should be 128 samples»

Discussion thread on the list:
http://lists.w3.org/Archives/Public/public-audio/2012AprJun/thread.html#msg461

[olivierthereaux]

Original comment by Olivier Thereaux on W3C Bugzilla. Mon, 09 Jul 2012 13:31:03 GMT

The discussion continues on the mailing-list:
http://lists.w3.org/Archives/Public/public-audio/2012JulSep/thread.html#msg1

And Robert raised a related issue about the lookahead in the DynamicsCompressorNode:
http://lists.w3.org/Archives/Public/public-audio/2012JulSep/0019.html

[olivierthereaux]

Original comment by Olivier Thereaux on W3C Bugzilla. Thu, 13 Sep 2012 09:48:49 GMT

This was discussed at the 12th Sept 2012 teleconference.

Suggested resolution: circular connections are allowed if there is a delay node present. If the delay is too small, the implementation should clamp it to a minimum, on a per-node basis.

There were two suggested resolutions for the minimum delay:

• one to specify the minimum as a block of 128 samples (which would make things sound differently on platforms with different sample sizes, but that was deemed acceptable in the same way as graphics look different on platforms with different frame rates and power).
• The other was to not specify it and let implementations choose (and, I assume, expose?) their minimum delay.

[olivierthereaux]

Original comment by Matthew Paradis on W3C Bugzilla. Tue, 18 Sep 2012 11:07:38 GMT

If circular connections (without delay) are allowed it may be worth considering raising an exception when they are detected. Software such as Pure Data and Max/Msp do this as well as zeroing the output.
Without the exception it may make the debugging process longer.

[olivierthereaux]

Original comment by paul@paul.cx on W3C Bugzilla. Fri, 06 Sep 2013 14:36:25 GMT

Duping against the most recent bug with the latest developments.

*** This bug has been marked as a duplicate of bug 23037 ***