Re: [Audacity-devel] Reassigned spectrograms

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

I'm just wondering why we are seeing so many new features introduced
for the 2.1.2 release. I thought that this release was about updating
to Wx3. My concern with so many changes in this release is that either
quality suffers or the release is seriously delayed. Perhaps James can
comment and reassure us that it is all in hand?

Steve

On 17 August 2015 at 15:40, Paul Licameli <pau...@gm...> wrote:
> I don't think it's "experimental" any more, I think I got all the math right
> now.
>
> There are opportunities for more efficiency.  It is true that caching of
> results leaves something to be desired for some changes of view, but that is
> already true of spectrograms generally.  There is no caching of any
> spectrograms for changes of zoom level.  There is some caching only for
> scrolling left and right without changing the zoom, and that much won't work
> now with reassignment.
>
> I consider any such effort for performance a future project.
>
> PRL
>
>
> On Mon, Aug 17, 2015 at 10:28 AM, Steve the Fiddle
> <ste...@gm...> wrote:
>>
>> 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
>> >
>> >
>> >
>> > ------------------------------------------------------------------------------
>> >
>> > _______________________________________________
>> > audacity-devel mailing list
>> > aud...@li...
>> > https://lists.sourceforge.net/lists/listinfo/audacity-devel
>> >
>>
>>
>> ------------------------------------------------------------------------------
>> _______________________________________________
>> audacity-devel mailing list
>> aud...@li...
>> https://lists.sourceforge.net/lists/listinfo/audacity-devel
>
>
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> audacity-devel mailing list
> aud...@li...
> https://lists.sourceforge.net/lists/listinfo/audacity-devel
>