Sorry, that should have been IFFT not SFFT.
About the windowing you are doing on the residual: are you multiplying
by the *inverse*? Is this window normalized?
Rich E wrote:
Xavier,
Its starting to get clearer, but I still have a couple questions as I
am definetaly not doing the resynthesis correct yet (I am getting a
periodic pitch.. not sound).
The analysis window, which by default is a BlackmanHarris92
with a 75% overlap. You need to multiply by the
inverse of this window after the SFFT.
sorry for having to ask, but what is an SFFT? If it is the same as an
STFT or FFT, at which point do I do this? I was under the impression
from one of Serra's publications that all I had to do with
resynthesize the residual FFT, but don't have to do any more FFTing.
If this is an IFFT, my attempt is on the right track, but I am still
not getting a noise sound. I am windowing the residual IFFT by a 75%
overlap and multiplying it by the BlackmanHarris92 window, then
re-windowing the result with a 50% overlap and multiplying by a
triangle window. But my result is pitched, and this changes if I
change the overlap.
Can anyone see what I am doing wrong?
regards,
rich
And then a completely independent
triangular window with a size equal to twice
the analysis hop and overlap 50%. This is the one in charge of
getting a
smooth overlap and add process in place.
Hope it helps.
X
Rich E wrote:
> Okay, I didn't think of looking for the overlap size by checking the
> timestamps, but that seems obvious now.. thanks! I have found there
> are many things preventing the SDIF files from being used in
real-time
> (such as the 1TRC frames not containing birth and death
information).
> So I am already buffering the data in a format that can be used in
> real-time, so finding the overlap before sysnthesis-time
shouldn't be
> a problem.
>
> However, I do not see the 1WIN matrix within the SMS-produced files.
> I assumed it is a triangle window with an overlap factor of 2
(this is
> the default settings in SMSTools), but of course this can be
changed,
> in which case I would not know how to find the windowing function.
> But I tried these settings without success (in comparison to
> SMSTools-produced residual sound), so I am still looking for the
> correct ones.
> cheers,
> rich
> On Dec 14, 2007 6:30 PM, Richard Dobson
> <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>
> <mailto:[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>>> wrote:
>
> Rich E wrote:
> > Okay, sorry for getting into too much pd stuff... I
basically just
> > need to know what needs to be done to the 1STF data before
I can
> > synthesize it. Is it ready to go, or is windowing still
necessary?
> > Should the frames be overlapped?
> >
>
> It's plain real/imaginary DFT data. SO in that sense yes it is
> ready to
> go straight into the IFFT. It will almost certainly require
windowing.
> If you haven't already done so, you will neded to check the
formal
> definition of the 1STF format e.g. at:
>
> http://www.cnmat.berkeley.edu/SDIF/FrameTypes.html#1STF
>
> SDIF is famous/notorious for being particularly "loose" about
> definitions and content. In short, each frame (matrix) is
time-stamped
> (from the centre of the window, because they like doing
things that
> way), and you have to determine the overlap from that (which
means you
> have to read at least two frames before you can start rendering,
> so this
> is not a true real-time streaming format; one would assume the
> overlap
> is constant, but the format does not see the need to mandate
it);
> there
> should be a 1WIN matrix that defines the window to use. Beyond
> that, all
> I can say is "good luck"!
>
>
> Richard Dobson
>
>
>
>
>
>
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