Re: [Alsa-user] Aliasing due to resampling?

[Bill U. <un...@ph...>]

On Wed, 26 Jul 2006, James Courtier-Dutton wrote:

> Alfons Adriaensen wrote:
>>
>> To summarize, aliasing is the result of the _sampled_ nature of a
>> digital signal, not of its numerical (digital) form.
>>
>>
>
> That is true for your particular example, but aliasing artifacts can be
> introduced during digital signal processing.
> Most noticeably, when using digital signal processing to resample from a
> high sample rate to a lower sample rate.

This is true. But irrelevant in this example discussed in this thread. The
"aliasing" here is due to the HIGHLY distored nature of the signal. Such
distortion introduces higher harmonics and they are being aliased by the
sampling to lower frequencies. Ie, the aliasing is not the problem, the
horrendous distortion is.

In resampling one should first introduce a sharp cutoff filter to eliminate
all frequencies in the orginal above the sampling cutoff of the lower
sampling rate.  Anyway, the orginal statement is still correct. aliasing is
the result of sampling, not digitization.

>
>
> James
>
>
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