[linux-audio-dev] Arbitrary bufsizes in plugins requiring power of 2 bufsizes, Was: jack_convolve-0.0.10, libconvolve-0.0.3 released

Florian Schmidt mista.tapas at gmx.net
Fri Jul 1 12:28:11 EDT 2005


On Wed, 29 Jun 2005 23:07:24 +0200
fons adriaensen <fons.adriaensen at skynet.be> wrote:

> > Another very useful feature would be tail extension (combine convolution 
> > with traditional reverb processing to lighten the CPU load)
> 
> I don't think this requires special support from the convolution
> engine - it's jsut an application of it.
> 
> Suppose you have the start of a reverb response:
> (imagine the y-scale is logarithmic)
> 
>    |\
>    | \
>    |  |     
>    |  |
>    |  |
> ---------------------------
> 
> and you feed back the output with the correct gain and delay,
> then the result will be a complete exponential decay.
> 
> This is too simplistic, and will probably give a 'echo' like
> character to the reverb, but that's the principle. It should
> be applied to the first part of the reverb 'tail' only, not
> the early reflections. But you only need a short convolution.

To avoid the echo like character one could do some preprocessing.  Take
a chunk of the tail and make it constant volume (if it is decaying
exponential, this should be possible).

Then fiddle some more with it to make it loop cleanly. Then use that as
response and apply gain and do the feedback delay thing. This would
allow arbitrary envelopes on the tail.

Regards,

Flo

-- 
Palimm Palimm!
http://affenbande.org/~tapas/


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