[music-dsp] 2nd order biquad for envelope detector?
mdsp at smartelectronix.com
Fri May 21 07:31:38 EDT 2004
> // the very easy hard knee 1:N compressor
> double gain = 1.0;
> if (env > threshold)
> gain = gain - (env - threshold) * slope;
I think you want to have a linear slope *in dB*
this is what I do:
gain = 1.0f;
gain = (float)pow(env/thres, - cSlope); //compression
cSlope = 1.0 - 1.0/ratio; // ratio is in [1:40]
thres = pow(10.0,threshold/20.0); //threshold is in dB
this is equivalent to
- converting the enveloppe in dB
- applying the transfer function
- and converting it back to linear.
there's a chapter about that in the DAFX book.
More information about the music-dsp