Re: [Audacity-devel] Reassigned spectrograms

[Steve t. F. <ste...@gm...>]

Is this an experimental feature?

Steve

On 17 August 2015 at 15:18, Paul Licameli <pau...@gm...> wrote:
> As of
> https://github.com/audacity/audacity/commit/3ddbbd375d6963838b91fe2f54c91df96d90e79a
>
> Now reassignment is a third algorithm choice in spectrograms preferences and
> view settings.
>
> This is an algorithm that sharpens the results of a spectrogram.  It works
> by computing two extra FFTs using different windowing functions.  The
> contributions that the usual FFT makes to pixels on the screen, are in
> effect moved slightly using results of the other FFTs.  This can counteract
> both the "time smearing" and "frequency smearing" effects.
>
> But not only is this spectrogram about three times as costly to compute -- I
> also had to disable the caching that allows horizontal scrolling of
> spectrograms to go faster.  This sort of caching is important for
> scroll-scrub with spectrogram on.
>
> The zero padding of spectrograms that I implemented in the last version was
> meant to accompany this.
>
> Try it out with tones and chirps -- you will find just a thin bright line,
> even if your window size is small!
>
> Try it with an impulse -- you will find a bright vertical line, even if your
> window size is large!
>
> Try it with real world examples -- and it is true there are strange
> artifacts from "cross terms" if you have two or more sources of sound, or
> inharmonic sounds, which make a sort of gauzy pattern as in this article.
> https://en.wikipedia.org/wiki/Reassignment_method
>
>
> PRL
>
>
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