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Instrument Control: Sensing and Control

follow


  kr      follow     asig, idt


Description

Envelope follower unit generator.

Initialization

idt – This is the period, in seconds, that the average amplitude of asig is reported. If the frequency of asig is low then idt must be large (more than half the period of asig )

Performance

asig – This is the signal from which to extract the envelope.

Example


  k1      line      0, p3, 30000    ; Make k1 a simple envelope

  a1      oscil     k1, 1000, 1     ; Make a simple signal using k1

  ak1     follow    a1, .02         ; ak1 is now like k1

  a2      oscil     ak1, 1000, 1    ; Make a simple signal using ak1

          out       a2              ; Both a1 and a2 are the same

To avoid zipper noise, by discontinuities produced from complex envelope tracking, a lowpass filter could be used, to smooth the estimated envelope.

Author

Paris Smaragdis
MIT, Cambridge
1995


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Instrument Control: Sensing and Control