[net.audio] Digital filter

jlg@lanl.ARPA (12/01/84)

> ( line eater, line eater, eat me a line. Oh, while your at it, one for me too)
>
> " A digital transversal filter is used for the filtering after
> oversampling.  To understand the operation of the filter, we can
> think of it as consisting of 96 elements, while the delay in each
> element is (176.4 * 1000) ** -1s, i.e. a quarter of the sampling
> period or 1/4 Ts.  Four times in each period the filter takes up new
> data.  At three of these four times, the content of this data is
> zero, since the oversampling is done by the introduction of
> intermediate samples of value zero.  This means that only 24 of the
> 96 elements are filled at any one time.  The contents of each
> element are multiplied by a coefficient c.  The filter provides data
> at a rate of 176.4 kHz; each number is the sum of 24 non-zero
> multiplications.  In this way the filter always calculates three new
> sample values at the locations of the zero samples."

In other words, it's a 96 element discrete convolution integral implemented
in hardware.  Just what you'd expect a digital filter to look like.