One issue I find with 2N is that if you downshift by more than one octave
you get gaps between the grains. In such case I'm thinking you may use
something like 3N or 4N or 5N so that the output grains also have ample
coverage on the time axis. For example if you choose the smallest kN larger
than 2M, you'll safeguard at least 50% overlap rate in the output.
Xue
-----Original Message-----
From: robert bristow-johnson
Sent: Tuesday, October 22, 2013 12:13 AM
To: A discussion list for music-related DSP
Subject: Re: [music-dsp] PSOLA pitch shifting - resample or not?
hey, thanks for picking this up, Rob. i am still a little bleary-eyed
from the AES convention that ended yesterday.
On 10/21/13 3:56 AM, Robert Bielik wrote:
Hi again Xue,
Robert Bielik skrev 2013-10-19 16:14:
No. The formant is preserved just by NOT resampling the original signal.
The pitch of the signal is only dependent on the periodicity
of each wave "granule", which is pretty much a windowed snapshot of the
original signal with length 2*N where N is the original periodicity.
Further to the point, the windowed granule size should be 2*min(N,M) where
N is original periodicity and M is target periodicity.
this is interesting, but i am not so sure i agree with it. i've always
been going under the assumption that the grain size is 2N, twice the
length of the input period (and overlapping complementary windows so
that at a shift of 0 cents, there is perfect reconstruction of the
original). but i always thought that if upshift, there would be more
than 2 overlapping grains. for a maximum of 1 octave up, i've used a
maximum of 4 overlapping grains.
but i am *very* interested to find out if/that my previous M.O. is wrong.
--
r b-j r...@audioimagination.com
"Imagination is more important than knowledge."
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