On Tue, Oct 17, 2006 at 10:04:20PM +0100, Dan Mills wrote:
> but at 44.1, there just is not the bandwidth in either
> the control or AUDIO channels to alllow fast gain
> changes. Therefore we need to upsample both the audio
> and the control data (albiet that the control
> upsampler can get away with a lot less bandwidth then
> the audio one).
If the control signal is derived from the upsampled input
to the compressor, that is taken care of.
> ...
> With both the audio and control bandlimited to 0.25 *
> FS, we can safely multiply them, any more then that
> (split any way you like) and it all falls apart.
Yes; that more or less makes 2x upsampling essential.
> With respect to viewing the attack and decay logic as
> a LPF, this is only the case if the same timeconstant
> applies to both (seldom the case), as otherwise there
> is a discontinuity in the rate of change at the
> transition which will itself generate HF splatter.
Isn't there always a discontinuity here anyway? When it changes from
attack to decay the rate of gain change switches suddenly from
negative to positive. A bandwidth limit on the control signal
should take care of that, as long as the cutoff is steep enough.
John
Received on Wed Oct 18 04:15:03 2006
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