Description

This opcode attempts to extract the AM and FM signals off a quadrature signal (e.g. from a Hilbert transform).

Syntax

am, af fmanal are, aim

Performance

are -- real (cosine-phase) input signal

aim -- imaginary (sine-phase) input signal

am -- amplitude modulation envelope

af -- frequency modulation envelope

fmanal takes a signal in quadrature (real, imag) and outputs the estimate AM and FM signals. The former is the modulus of each input sample pair (|re + j*im|) and the latter the derivative of arg(re + j*im). Each sample of the output is the estimated instantaneous amplitude and frequency of the input signal.

Example

Here is an example of the fmanal opcode. It uses the file fmanal.csd.

<CsoundSynthesizer>
<CsOptions>
</CsOptions>
<CsInstruments>

sr = 44100
ksmps = 64
nchnls = 2
0dbfs = 1

instr 1

asig oscili p4, p5
a1,a2 hilbert2 asig,1024,256
am,afm fmanal a1,a2
ktrig metro 2
printf "AM=%.3f FM=%.1f\n",ktrig,k(am),k(afm)
  outs a1, a2

endin


</CsInstruments>
<CsScore>
i1 0 10 0.5 440
</CsScore>
</CsoundSynthesizer>

Credits