[webkit-dev] FFT normalization in RealtimeAnalyser

Simon Fraser simon.fraser at apple.com
Fri Aug 15 08:38:26 PDT 2014

Please file a bug at bugs.webkit.org.


On Aug 15, 2014, at 1:56 AM, Info <info at wothke.ch> wrote:

> This seems to be a bug... that has been fixed in Chromium: see chromium\src\third_party\WebKit\Source\modules\webaudio
> Zitat von Info <info at wothke.ch>:
>> In order to understand the idiotic differences between the data ranges of the AnalyzerNode's getFloatFrequencyData() and getByteFrequencyData() APIs I finally found myself analyzing the WebKit sources: https://github.com/WebKit/webkit/blob/master/Source/WebCore/Modules/webaudio/RealtimeAnalyser.cpp
>> What surprises me there is the:
>>    const double magnitudeScale = 1.0 / DefaultFFTSize;
>> which is used to normalize the FFT results (see RealtimeAnalyser::doFFTAnalysis()).
>> Should the correct scaling factor not rather be: 2/actualFftSize?

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