follow — Envelope follower unit generator.
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 )
Here is an example of the follow opcode. Play follow.csd, and beats.wav
Example 366. Example of the follow opcode.
See the sections Real-time Audio and Command Line Flags for more information on using command line flags.
<CsoundSynthesizer> <CsOptions> ; Select audio/midi flags here according to platform -odac ;;;realtime audio out ;-iadc ;;;uncomment -iadc if realtime audio input is needed too ; For Non-realtime ouput leave only the line below: ; -o follow.wav -W ;;; for file output any platform </CsOptions> <CsInstruments> sr = 44100 ksmps = 32 nchnls = 2 0dbfs = 1 instr 1 asig soundin "beats.wav" outs asig, asig endin instr 2 ;envelope follower as soundin "beats.wav" as = as*.7 ;reduce volume a bit at tone as, 500 ;smooth estimated envelope af follow at, p4 asin poscil3 .5, 440, 1 ; "beats.wav" provides amplitude for poscil asig balance asin, af outs asig, asig endin </CsInstruments> <CsScore> ;sine wave. f 1 0 32768 10 1 i 1 0 2 i 2 2 2 0.001 ;follow quickly i 2 5 3 0.2 ;follow slowly e </CsScore> </CsoundSynthesizer>
To avoid zipper noise, by discontinuities produced from complex envelope tracking, a lowpass filter could be used, to smooth the estimated envelope.