[music-dsp] AMDF shortcuts for SOLA time stretching?
rossb-lists at audiomulch.com
Tue Apr 22 04:53:15 EDT 2008
> Well, who would compute an ACF in the time domain anyway? ;)
Well.. if your synthesis buffer size (ie hardware buffer size) is on the
order of 64 samples, may not be a multiple of your FFT frame rate, and may
vary (eg if you're a plugin) then doing longish FFTs without CPU
spikes/irregularities is obviously a non-trivial matter. Either I'm ignorant
of something you can tell me, or you have a nice FFT implementation that
gives constant CPU load ;-)
>> I'm wondering though, when you talk about "workload" are you including
>> both the analysis and resynthesis workloads? I notice your web pages talk
>> about optionally pre-computing the analysis step..
> For the PSOLA-type stretching, you can separate the pitch mark computation
> from the synthesis and run the synthesis alone with very insignificant
> workload. But for a phase-vocoder, we don't separate analysis and
> synthesis - it's only one processing step. When I compared workload, I was
> referring to both algorithms doing analysis and synthesis at "the same
>> ----- Original Message ----- From: "alexander lerch" <lerch at zplane.de>
>> To: "A discussion list for music-related DSP"
>> <music-dsp at music.columbia.edu>
>> Sent: Tuesday, April 22, 2008 12:44 AM
>> Subject: Re: [music-dsp] AMDF shortcuts for SOLA time stretching?
>>> Hi Ross,
>>> Ross Bencina wrote:
>>>> My extremely vague impression is that a good spectral-peak-processing
>>>> time stretcher (such as the one published by Jordi Bonada in 2001 I
>>>> think) consumes about 50% of a current generation IA32 CPU -- that's
>>>> extrapolating from how it was performing in 2001.
>>> That's not necessarily true I would say, but heavily depends on how you
>>> optimize it (algorithmically and CPU-wise). As for our time-stretching
>>> engines, our PSOLA based approach (élastique SOLOIST) roughly takes as
>>> much workload as our phase vocoder based engine (élastique efficient) in
>>> a "real-time" situation, and you can run far more than two instances at
>>> once for both of them.
> dipl. ing.
> alexander lerch
> d-10965 berlin
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