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Re: [web-audio-api] (LinearConvolution): Linear convolution effect is defined by Wikipedia (#125)

From: Olivier Thereaux <notifications@github.com>
Date: Wed, 11 Sep 2013 07:29:48 -0700
To: WebAudio/web-audio-api <web-audio-api@noreply.github.com>
Message-ID: <WebAudio/web-audio-api/issues/125/24244374@github.com>
> [Original comment](https://www.w3.org/Bugs/Public/show_bug.cgi?id=17403#2) by Marcus Geelnard (Opera) on W3C Bugzilla. Tue, 12 Jun 2012 08:43:52 GMT

I think this mail-comment from the original issue was overlooked:

The new document [1] contains valuable information, but isn't what this  
issue was about. If linear convolution need not be defined, then the issue  
should be closed as invalid.

Not everyone reading the spec will have a background in signal processing,  
e.g. we want our QA to be able to write tests with little effort. We  
suggest to define the output y in terms of the input x and the [possibly normalized] impulse  
response g as a summation formula or pseudo-code such as:

y[n] = 0
for i in 0...N-1:
   y[n] += x[n-i] * g[i]

This leaves no room for ambiguity about the phase of the output signal.

ISSUE-70 will need to be resolved for the above formula to make sense,  
though, as the input and impulse response may have different numbers of  

[1] https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/convolution.html

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