Re: Logarithmic Interpolation


Michel Rouzic skrev:
Martin Eisenberg wrote:
Michel Rouzic wrote:

I didn't wanna talk about this too much, because I rather
realize by myself if it's a dumb idea than be told, but my plan
is to *try* using that to perform pitch shift/time stretch.

my basic idea is, get the FFT of the signal you want to shift,
interpolate the FFT logarithmically, shift the contents towards
the left or the right depending on what you want to obtain,
interpolate back to linear form, IFFT. of course, i'm definitly
not sure and quite sceptical about the odds of obtaining the
wanted result, but I think it's worth trying.

Since adding to log frequency is the same as multiplying linear
frequency you can get the same thing with just one interpolator,
used to resample the scaled spectrum.

oh yeah, that's right, but, if I do that, wouldn't the result be just
like interpolating the signal in the time-domain?

Nope. Interpolation (i.e. sampling the spectrum on a denser grid)
corresponds to elongating the duration in time domain.

You indicate above that this is an academic exercise, and as such
it makes perfect sense. However, I think you are doing things
a bit too complicated. Why not check the properties of spectrum
interpolation etc in linear scale first, and switch to logarithmic
after you've got some more experience?

Somehow, I think there is a bit confusion about what effects are
caused interpolating the spectrum, and what effects are caused
by working in logarithmic scale.

Divide and conquer.

Rune

.

Relevant Pages

  • Re: Logarithmic Interpolation
    ... interpolate back to linear form, ... Interpolation (i.e. sampling the spectrum on a denser grid) ... corresponds to elongating the duration in time domain. ... If you (in linear scale) interpolate to find new spectrum coefficients ...
    (comp.dsp)
  • Re: DSP - General Question (this is not too awful far OT)
    ... Suppose one has a good FFt program, and took the FFt of 5 real data ... and then interpolate using a sinc kernel (and maybe scale with 5/8 or ... May have to also either reflect or replicate the spectrum ... same result as the odd case even if N is even. ...
    (comp.dsp)
  • Re: zero-padding and normalization for fft
    ... analysis resolution at all in frequency domain. ... so yield a better look of the spectrum. ... It doesn't increase the resolution in terms of being able ... interpolate accurately enough to often allow the measurement ...
    (comp.dsp)
  • RE: Linear Interpolation in excel
    ... Assuming your data is linear, ... Value to interpolate in C1. ... Dim y0Num, y1Num, vlpos As Integer ... Dim foundFlag As Boolean ...
    (microsoft.public.excel.programming)
  • Re: Interpolation Problem
    ... Interpolate how? ... This is simple coordinate-wide linear interpolation. ... on a tessellation of your domain space. ... successive calls to griddata3. ...
    (comp.soft-sys.matlab)