Am 10.11.2018 um 00:19 schrieb gm:
FFT size is 4096, and now I search for ways to improve it, mostly
regarding transients.
But I am not sure if that's possible with FFT cause I still have
pre-ringing, and I cant see
how to avoid that completely cause you can only shorten the windows on
the low octaves so much.
Maybe with an assymetric window?
If you do the analysis with a IIR filter bank (or wavelets) you kind
of have assymmetric windows, that is the filters
integrate in a causal way with a decaying "window" they see, but I am
not sure if this can be adapted somehow
to an FFT.
I just tried this and it works well in the analysis, pre-ringing is
reduced, everthing sounds more compact
Together with the ERB scaling now it even kind of works on bass drums.
They are not perfect, but much better.
The windows I am using for this:
if wn(t) is a Hann window and 0 <= t <= 1
then window is wn(sqrt(1-t))
The properties of the window can be found in
"Asymmetric Windows and their Application in Frequency Estimation"
It's not particularly good compared to others, sides fall off with -12
dB/octave but it's shape
is the most skewed one of the windows given in the paper with the
fastest rise
and the rightmost peak so it really makes a difference.
Downside is that now I also have to use this window for peak tracking
and frequency estimation
where a better rolloff and a more narrow peak would be desireable, but
the partials need to be in synch
with the amplitudes so I need the same window shape.
An up side is that it scales so that the peak stays in place for all sizes.
Another downside is that ERB scaling makes the high frequencies quite
hissy, they seem too
pronounced also because they ring longer than in the original when you
dont use a really
high overlap rate, like 78.
Still I am looking for window that might have better properties so any
input on that is apreciated.
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