W3C home > Mailing lists > Public > public-audio@w3.org > April to June 2016

Re: two questions about FFT/IFFT

From: Matt Diamond <mdiamond@jhu.edu>
Date: Tue, 12 Apr 2016 20:04:58 -0400
Message-ID: <CADdpXtuMhUvtOVob7kTmZL5MGMfT5fTybY+Dri_zfbOFd4gg8A@mail.gmail.com>
To: Raymond Toy <rtoy@google.com>
Cc: "public-audio@w3.org" <public-audio@w3.org>
Thanks for the reply. This might be a silly question, but is there an
equation I can use to reliably calculate the actual frequency range of each
bin returned by the analyser? I get an array of decibel values but I don't
know exactly what frequencies they correspond to.

Matt

On Tue, Apr 12, 2016 at 7:32 PM, Raymond Toy <rtoy@google.com> wrote:

>
>
> On Tue, Apr 12, 2016 at 2:24 PM, Matt Diamond <mdiamond@jhu.edu> wrote:
>
>> 1) Is it possible to do a non-realtime spectral analysis of a
>> BufferSource using an AnalyserNode with an OfflineAudioContext?
>>
>
> Yes, but you probably need to use suspend/resume to get correct timing.
>
>>
>> 2) Is it possible for me to use a PeriodicWave to convert an array of
>> frequency data from the Analyser Node back into a time-domain waveform? It
>> seems like this isn't possible.
>>
>
> Right.  The analyser loses the phase information so you can't get the
> original back.
>
>>
>> Basically I'd like to come up with a web-based version of the spectral
>> averaging technique that R Luke DuBois employed on Timelapse... averaging
>> the spectral content of an entire buffer and then reproducing that content
>> as a sustained drone. Is that possible yet with the Web Audio API as it
>> currently exists?
>>
>> Thanks,
>> Matt Diamond
>>
>
>
Received on Wednesday, 13 April 2016 00:05:28 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 13 April 2016 00:05:29 UTC