In essence WSOLA and SOLA are only for Time Scale Modification...

WSOLA - Applies synchronization in the analysis stage of OLA, so input
frames are selected based on waveform similarity, keeping the output at a
constant rate!

SOLA - Works like WSOLA but  applies synchronization in the output, so a
input frame are selected and the synchronism occurs at the output (where
the input frame is more like the current output frame).

As far as I know, these are the differences between SOLA and WSOLA

I'd love to be right, lol.

But if I am correct I have already seen several implementations of WSOLA
running as SOLA (of course the two algorithms are very similar, they only
have distinction if they will use correlation in the input or output).



On Tue, Feb 26, 2019 at 8:54 AM Ross Bencina <>

> Hi Alex,
>  > I can't understand the difference between  SOLA, PSOLA and WSOLA.
> I'll attempt a partial answer:
> I think PSOLA and WSOLA are clearly distinct.
> PSOLA involves identifying a time varying pitch (fundamental frequency)
> track for the input, segmenting the input signal into (possibly
> overlapping) windowed grains which are synchronous to this fundamental
> frequency (e.g. grains that are centered on glottal pulses) and then
> altering the rate at which the grains are assembled in the output stream.
> WSOLA involves breaking the signal into grains using some method (e.g.
> constant duration grains), then concatenating input grains to the output
> stream with relative phase adjusted according to two criteria: (1) on
> average, the input must be consumed at a rate that maintains the
> timescaling factor; (2) the source material should be mixed (with
> windowing) into the output stream in a way that minimizes local error
> over the crossfade region (i.e. to minimize phase cancellation) -- if
> the signal is strongly periodic, and the parameters are just right, this
> will fairly nicely keep the period of the source waveform, but it lacks
> sub-sample-accurate phase alignment I think. You can add enhancements
> such as trying to avoid mixing the same transient into the output stream
> more than once.
> Not sure what SOLA is.
> Ross.
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