Talk:Compressor
Steve, is this correct?
Compressor settings:
- Threshold -12 dB
- Ratio 4:1
- Noise Floor -42 dB
- Blue graph is IO characteristic for "compress based on peaks" OFF and "make-up gain" OFF
- Red graph is IO characteristic for "compress based on peaks" ON and "make-up gain" OFF or ON
- Green graph is IO characteristic for "compress based on peaks" OFF and "make-up gain" ON
-- Bill
The characteristics when "Make up gain" is on cannot really be shown on this type of diagram.
Unlike (most) hardware compressors, the "make-up" gain is not a fixed amount to compensate for the lower output, but is a Normailize function. The amount of gain depends on the peak level of the audio after compressing. The solid red line is approximately the effect of normalizing (make-up gain to 0dB) if the uncompressed signal had a peak of 0dB.
In the diagram below there are several alternative "post-make-up gain" plots drawn. The lower the peak amplitude after compression, the more make up gain is applied. The make-up gain would be described better as "Normalize to 0dB after compression".
This also applies to "Make-up gain for 0 dB after compressing" when using "Compress based on Peaks".
When Compress based on Peaks is selected, the threshold will appear to be at a different level, because it is working with peak values rather than RMS values. It's a bit tricky to show in this kind of diagram because we're mixing peak and rms measurements.
When compression is based on RMS, a threshold setting of -12dB will begin compression at an RMS value of -12dB (roughly -9dB peak). When compression is based on Peak, a threhold setting of -12dB will begin compression at a PEAK value of -12dB.
I'll add some better diagrams for upward vs. downward compression shortly.--Steve the Fiddle 17:18, 20 November 2009 (UTC)
