[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Octal-dev] Fourier Transforms and samples
From: |
Steve Mosher |
Subject: |
Re: [Octal-dev] Fourier Transforms and samples |
Date: |
Mon, 22 May 2000 01:05:26 -0300 |
On Fri, 19 May 2000, address@hidden wrote:
> Do you mean by performance: the processing time required (most like-
> ly), or the resulting audio quality?
Performance-wise.
> But before going onto these questions, it appears that you have im-
> plemented or found an STFT implementation. If this is code/software,
> where can it be found?
I've found some nice info on STFT (www.dspdimension.com), there's
some example code there as well.
> In terms of speed, if only the generating phase (reverse Fourier
> Transform) from a predetermined Fourier description could be used,
> the forward transform phase could be avoided. The STFT method de-
> scribed (thanks to your previous web reference) on
Hai, this is what I'm talking about...
<kersnip>
> As just suggested, the forward transform process should provide a
> precise Fourier description to minimize overall processing time but
> will obtain a trade-off between processing time and precision of re-
> sult--as seen in the increase of FFTs per sample--to minimize Fouri-
> er description distortion (with respect to the original sound).
Hmm... sounds right.
> But finally, the STFT process will obtain a floor amount of distor-
> tion (some necessary portion of distortion) because of the inherent
> block nature of the FFT. This effect will be most apparent at high,
> transient frequencies (discussed in the parameter trade-offs in
> (1)).
Yeah, I'm aware of this. Not too worried, unless it becomes
unusable at the point where it can be done in real time.
> As mentioned by Davíð B. Franzson, obtaining a precise Fourier de-
> scription in something close to real-time will require a significant
> computational ability. Fourier processing is highly parallel and may
> be pipelined, such that I expect a Beowulf Cluster would approach
> the real-time result. A one megahertz Beowulf node using AMD's
> Athlon is closing in on $1,000. This kind of Fourier processing
> equipment might be suitable for recording studios where the time re-
> quired to record and then playback would minimize the processing de-
> lay issue. The computationally intensive forward transform should be
> able provide a simplified, precise Fourier description within the
> record to playback time delay and such that the reverse transform
> could be processed in real time. Or is someone already doing this?
There ought to be sound cards that do this... to boot, clusters
are impractical for home use, not so bad for studio use (good idea,
actually), and horrible for set use. It would be -sweet- to see a cluster
devoted to processing FFTs -- it could be optimized to do simply that, and
a higher load could be placed on it. It would be more useful to have it
perform all your DSP... then again, wouldn't it be more efficient (and
cheaper) to rip apart a PSX2 and use the sound syntesizer? I still want to
see Octal ported to it =). I think it would be the best platform thus far
for such a program...
Thanks for your reply, highly detailed.
--
Heuristics are bug ridden by definition. If they didn't have bugs, then
they'd be algorithms.
[Octal-dev] OCTAL and literate programming, Dave O'Toole, 2000/05/19
Re: [Octal-dev] OCTAL and literate programming, Steve Mosher, 2000/05/22