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Re: fftSize requirement for RealtimeAnalyserNode

From: Alistair MacDonald <al@signedon.com>
Date: Thu, 22 Mar 2012 11:28:41 -0400
Message-ID: <CAJX8r2k8UXT3JHkt9SMZQJPV_o8o-56M+vEi=5KKDz5tCwxwmw@mail.gmail.com>
To: Jussi Kalliokoski <jussi.kalliokoski@gmail.com>
Cc: "Wei, James" <james.wei@intel.com>, "public-audio@w3.org" <public-audio@w3.org>
Issue-7 created:  https://www.w3.org/2011/audio/track/issues/7

Should arbitrary FFTs sizes be possible in the RealtimeAnalyserNode?
Currently they are limited to a Power of Two. Jussi suggests we will get
better performance from the API if we changed this.




On Thu, Mar 22, 2012 at 7:07 AM, Jussi Kalliokoski <
jussi.kalliokoski@gmail.com> wrote:

> I hadn't actually even noticed this. Interesting. Why exactly should the
> value be a power of two? It seems to me like the spec shouldn't say
> something like this. Sure, power of two FFTs are easier to implement than
> others, but IIRC they are rarely the fastest. And if we aim for
> performance, the implementation should probably be using something like
> FFTW that allows for any buffer size anyway.
>
> Cheers,
> Jussi
>
>
> On Thu, Mar 22, 2012 at 11:02 AM, Wei, James <james.wei@intel.com> wrote:
>
>>  ** **
>>
>> For fftSize in RealtimeAnalyserNode in the spec, it only says the value
>> must be power of 2.****
>>
>> ** **
>>
>> But in fact in the implementation, the value must be limited in the range
>> of [128, 2048], and it will throw the exception if illegal value of fftSize
>> is set.****
>>
>> ** **
>>
>> Which should be documented in the spec. ** **
>>
>> ** **
>>
>> ** **
>>
>> Best Regards ****
>>
>> ** **
>>
>> James ****
>>
>> ** **
>>
>> ** **
>>
>
>


-- 
Alistair MacDonald
SignedOn, Inc - W3C Audio WG
Boston, MA, (707) 701-3730
al@signedon.com - http://signedon.com
Received on Thursday, 22 March 2012 15:29:15 GMT

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