🚀 go-pugleaf

lance@motcsd.csd.mot.com (lance.norskog) writes:

>Ok, now we're getting somewhere.  The SPUT sound operating system
>for DOS (shareware by Adrienne Cousins) has high-pass and low-pass
>filtration options for playing back sound samples.  SPUT is a DOS
>TSR (background program) comprising 5K of 8086 code, so we know
>it doesn't have 13,000 coefficients.

>If interpolation is being used for the low-pass operation, is it
>also being used for the high-pass problem?

I don't know this software, so I'm guessing.  It is probably not
interpolation, but a simple digital filter.  These work by taking
the last N samples, multiplying them by a bunch of constants
a[1],...,a[n] and adding the results.  You can (optionally) take
the computed output and use it in the computation on the next
sample as well.  You only need a few coefficients (maybe 10) to
get low-pass, high-pass, and bandpass responses, with responses
like analog audio equipment. The zillion coefficient case is only
when you are trying to do something tricky.

-Lou Scheffer