[sdiy] what is the amplitude envelope of a signal

[john mahoney]

Harry say...
> OK then... lets make a formal definition  ;^P
Good idea.

> The ripple vs speed tradeoff is a killer. [snip]
> This is a real nightmare problem.  If I could stand
> it,  I'd think about running some delay in the signal to
> allow the circuit to 'look into the future' and
> adapt... but I fear even a millisecond is too much

Fast analog EGs have about 1 ms attack, but we can probably spare a few ms
if needed.

You have to trade reaction time (speed) for smoothing in a simple envelope
follower, but a digital device can have complex smoothing algorithms. If the
signal delta is greater than a certain amount (or percentage) then you can
change the envelope instantly. If the delta is less than a certain
threshhold then you only change the envelope a certain amount (a variable
slew rate, which can be linear, expo, etc.).

You can also maintain moving averages (pos & neg) several samples in length,
which can be compared to the instantaneous measurements. For example, if the
difference between the average and instant peaks exceeds a threshhold, then
you do one thing; if not, you do something else.

I hope that makes sense, because I'm tired!
--
john