HI all,
At the time I had started two posts regarding 'RMS compressor' (the current post) and 'PEAK compressor':
http://www.dsprobotics.com/support/viewtopic.php?f=3&t=6274 They had received many views and comments. Some very interesting comments came from Martin Vicanek side (thanks) especially regarding the 'signal flow' of the 'side chain' (gain calculation) as well as the 'smoothing/filter' mechanism.
Side Chain Flow:Attached is another version of an RMS compressor. In this version the 'side chain' signal flow is more common (like Martin had suggested).
Ths signal (within the side chain) flow:
--> Energy Detector (RMS calculation) --> Time based smoothing (Attack and release) --> Lin2Db --> Transfer function -- Db2Lin
(see attached image).
Smoothing Filter Mechanism:The 'smoothing' mechanism is a simple first order LPF which (as discussed in this post
http://www.dsprobotics.com/support/viewtopic.php?f=3&t=6274 ) far from ideal.
I still have doubts about this issue.
For instance, in Abelton Live's compressor (and other many examples), there are three 'latency settings': 0ms, 1ms, 10ms.
For the 0ms - one can only think of an IIR smoothing mechanism running inside (1st or higher order)?
Is this correct?
I agree that if latency (look ahead) is allowed the FIR (moving average) followes and therfore 'sounds' much better.
But what is the case of ZERO latency ?