Re: [LAU] octaver (plugin) for bass

From: hermann meyer <brummer-@web.de>
Date: Fri Jun 13 2014 - 10:04:59 EEST

Am 13.06.2014 00:16, schrieb Fons Adriaensen:
> On Thu, Jun 12, 2014 at 10:41:00AM +0100, Chris Cannam wrote:
>
>> One warning, the method described in it is patented -- I had to do a
>> hasty rewrite in some early Rubber Band code. I don't know whether
>> anyone enforces the patent though.
> Indeed... I'd be surprised if the patent is actually enforced...
> There's also a collection of related patents by Fraunhofer..
>
>>> For code, maybe have a look at Rubberband which may contain
>>> interesting things (I don't know, never dared to look
>> Probably wise -- I expect it would horrify you. And of course this
>> application is an incredible time-sink simply because there's no right
>> way to do it. It's a subject that can surely drive you mad.
> It sure can. Meanwhile, since you tickled me, I did have a look.
> I've seen worse :-)
>
>> You gave a low-level example of the problem earlier (with neighbouring
>> frequency bins). Looking at it at a high level, you're basically trying
>> to synthesise a signal that corresponds to "what the same instruments
>> would have sounded like if they were playing slower" (or higher, or
>> whatever).
> There's a more fundamental problem behind this.
>
> Suppose you have a sine wave at some frequency F, modulated (i.e.
> multiplied) by say a 8 Hz sine wave. Assume we want to transpose
> an octave up. Now is this signal
>
> a) just a single frequency (F) with some amplitude modulation on it,
> or
> b) two signals, at F-8 and F+8 Hz.
>
> Mathematically, and in the analysis spectrum, these are just the
> same thing. It's a matter of interpretation. In case (a) you'd want
> a sine at 2*F with the same 8 Hz modulation on it. In case (b) the
> wanted output is two signals at 2*(F-8) and 2*(F+8) Hz. You have
> the choice of interpreting the 'detail' in either the time or
> frequency domains.
>
> For high F, our hearing would probably favour (a). But at low
> frequencies things could be different. 64 Hz and 80 Hz would
> make a nice major third...
>
>
> Ciao,
>

Thanks for your hints.

I've found a other interesting paper which seems to use the resampling
technique you've talked about in a earlier post.
   http://qmplus.qmul.ac.uk/mod/resource/view.php?id=305410
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Received on Fri Jun 13 12:15:01 2014

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