17 Oct
2006
17 Oct
'06
8:49 p.m.
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