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
