[CLAM] synthesizing SMS models in Pd
xavier at amatriain.net
Fri Dec 14 14:21:18 PST 2007
As Richard said the 1SFT data is ready to go into the IFFT. A different
story is what you need to do afterwards to
get a smooth synthesized sound. I am not sure what *window* you are
talking about because there are two involved in the
process. 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. 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.
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.
> On Dec 14, 2007 6:30 PM, Richard Dobson
> <richarddobson at blueyonder.co.uk
> <mailto:richarddobson at blueyonder.co.uk>> 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:
> 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
> is constant, but the format does not see the need to mandate it);
> 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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> CLAM at iua.upf.es <mailto:CLAM at iua.upf.es>
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