Subject: Re: [linux-audio-dev] Still I cannot understand why...
From: Paul Davis (pbd_AT_Op.Net)
Date: Thu Dec 20 2001 - 03:39:06 EET
>Just curious, but could somebody explain *how* delay lines can be used
>implement EQ? I have a strong maths background, but no DSP experience if
>that helps.
i'm not a dsp programmer, but its really quite simple. if you
feedback with a delay of just 1 sample, and attenutate both the
current and previous sample by 0.5:
y[n] = (0.5 * x[n]) + (0.5 * x[n-1])
you've just averaged the two values, which effectively smooths out
"jags" in the input signal. you can vary the attenuation coefficients
and the delay length and the number of delay lines to alter the kind
of smoothing, which is of course directly equivalent to filtering
certain frequencies out of the signal.
the actual details are extremely hairy though - there is a lot of
sophisticated math that goes into really good filter design, plus a
lot of subjective, non-double blind tested "opinion" :)
--p
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