[PD] Combat aliasing!

[Pierre Massat]

I m not sure i understand aliasing well... So anything that's sampled and
played back without altering the pitch would not suffer from aliasing? When
exactly does aliasing occur? during the DAC conversion, or before that?
Let's say i set a karplus-strong resonator to a frequency of 30 KHz
(assuming i'm a dog and i can hear a pitch that high), at a 44.1 KHz
sampling rate, than what happens? No aliasing at all?



2010/3/31 Derek Holzer <derek at umatic.nl>

> I was thinking about this the other day.... is it possible to have aliasing
> with Karplus-Strong? Because it's a delay line, nothing is being played back
> at any higher rate than it was sampled at, so no aliasing should be
> possible. Right? Math-gurus correct me if I'm wrong.
>
> Otherwise, any signal generator needs to be bandlimited or oversampled:
>
> http://en.flossmanuals.net/PureData/Antialiasing
> http://en.flossmanuals.net/PureData/GeneratingWaveforms
>
> Frank Barknecht has some spliced-transition trick he uses as well, I'm sure
> it will come up in a reply or two on this thread as well...
>
> D.
>
>
> On 3/31/10 6:27 PM, Pierre Massat wrote:
>
>> Hi!
>>
>> I ve been reading the on-going debate about interpolation for a few
>> days, and it just occured to me that i don't how go about avoiding
>> aliasing more generally than with band-limited wavetables. If i wanted
>> to play a sample at a pitch higher than the original, or if i wanted to
>> use a karplus-strong resonator to generate notes, what would be the
>> proper way of ensuring that no aliasing occurs? Do people generally use
>> low-pass filters with a cut-off somewhere below the Nyquist frequency?
>> Or is there a trick that one can use earlier on in the signal path of a
>> patch?
>>
>
> --
> ::: derek holzer ::: http://macumbista.net :::
> ---Oblique Strategy # 139:
> "Revaluation (a warm feeling)"
>
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