[linux-audio-dev] Paper on dynamic range compression

[John Rigg]

On Thu, Oct 05, 2006 at 09:01:19AM -0500, Andres Cabrera wrote:
> I was assuming that RMS measruments and windowed integration act as a 
> high pass filter, is this not true?

No, a low pass filter integrates and a high pass filter differentiates.

The audio signal is rectified before it can be filtered and used for
gain control, so there is no AC signal for the filter to act on,
just a varying DC level. The time constants for the filter
(eg. charge and discharge rates on a capacitor in an analog LP filter)
determine the rate at which the control signal can increase or
decrease, and hence the attack and decay times.

John