SOX-COMPAND

[GENERIC-FUNCTION]


OM-SoX
Function Reference
ARGUMENTS:
  - attack attack-time (secs) [default = 0.3]
  - release release-time (secs) [default = 0.8]
&key
 
  - transferfunction transferfunction describing changes from input to output levels over dynamic range of audio (bpf)  
  - softknee softknee (in dB) [default = 6]
  - makeup-gain makeup-gain (in dB) [default = -5]
  - minvolume an initial level for when companding starts [default = -90]
  - lookahead A delay in seconds. Allows the compander to effectively operate in a 'predictive' rather than a reactive mode [default = 0.02]
  - sox-append Append sox-effects/statistics to the processing chain.  

Description:

Compand (compress and/or expand) the dynamic range of the audio.

<attack> and <release> determine the time over which the instantaneous level of the input signal is averaged to determine its volume; <attack> refers to increases in volume and <release> refers to decreases. For most situations, <attack> should be smaller than <release> because the human ear is more sensitive to sudden increases rather than decreases in audio levels. Typical values are 0.3,0.8 seconds.

<transferfunction> is a breakpoint function describing compression/expansion over the dynamic range of the input signal.

<softknee> will round the points at where adjacent line segments on the transfer function meet by the specified amount.

<makeup-gain> is an additional gain in dB to be applied at all points on the transfer function which allows easy adjustment of the overall gain.

<minvolume> permits the user to supply a nominal level initially, so that, for example, a very large gain is not applied to initial signal levels before the companding action has begun to operate: it is quite probable that in such an event, the output would be severely clipped while the compander gain properly adjusts itself.

<lookahead> is a delay in seconds. The input signal is analysed immediately to control the compander, but it is delayed before being fed to the volume adjuster. Specifying a delay approximately equal to the attack/release times allows the compander to effectively operate in a 'predictive' rather than a reactive mode.



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