pitch
Prev | Orchestra Opcodes and Operators | Next

## pitch

pitch — Tracks the pitch of a signal.

## Description

Using the same techniques as spectrum and specptrk, pitch tracks the pitch of the signal in octave point decimal form, and amplitude in dB.

## Syntax

    koct, kamp pitch asig, iupdte, ilo, ihi, idbthresh [, ifrqs] [, iconf] [, istrt] [, iocts] [, iq] [, inptls] [, irolloff] [, iskip]

## Initialization

iupdte -- length of period, in seconds, that outputs are updated

ilo, ihi -- range in which pitch is detected, expressed in octave point decimal

idbthresh -- amplitude, expressed in decibels, necessary for the pitch to be detected. Once started it continues until it is 6 dB down.

ifrqs (optional) -- number of divisons of an octave. Default is 12 and is limited to 120.

iconf (optional) -- the number of conformations needed for an octave jump. Default is 10.

istrt (optional) -- starting pitch for tracker. Default value is (ilo + ihi)/2.

iocts (optional) -- number of octave decimations in spectrum. Default is 6.

iq (optional) -- Q of analysis filters. Default is 10.

inptls (optional) -- number of harmonics, used in matching. Computation time increases with the number of harmonics. Default is 4.

irolloff (optional) -- amplitude rolloff for the set of filters expressed as fraction per octave. Values must be positive. Default is 0.6.

iskip (optional) -- if non-zero, skips initialization. Default is 0.

## Performance

koct -- The pitch output, given in the octave point decimal format.

kamp -- The amplitude output.

pitch analyzes the input signal, asig, to give a pitch/amplitude pair of outputs, for the strongest frequency in the signal. The value is updated every iupdte seconds.

The number of partials and rolloff fraction can effect the pitch tracking, so some experimentation may be necessary. Suggested values are 4 or 5 harmonics, with rolloff 0.6, up to 10 or 12 harmonics with rolloff 0.75 for complex timbres, with a weak fundamental.

## Examples

Here is an example of the pitch opcode. It uses the files pitch.orc, pitch.sco and mary.wav.

Example 272. Example of the pitch opcode.

    /* pitch.orc */
    ; Initialize the global variables.
    sr = 44100
    kr = 44100
    ksmps = 1
    nchnls = 1

    ; Instrument #1 - play an audio file without effects.
    instr 1
      asig soundin "mary.wav"
      out asig
    endin

    ; Instrument #2 - track the pitch of an audio file.
    instr 2
      iupdte = 0.01
      ilo = 7
      ihi = 9
      idbthresh = 10
      ifrqs = 12
      iconf = 10
      istrt = 8

      asig soundin "mary.wav"

      ; Follow the audio file, get its pitch and amplitude.
      koct, kamp pitch asig, iupdte, ilo, ihi, idbthresh, ifrqs, iconf, istrt

      ; Re-synthesize the audio file with a different sounding waveform.
      kamp2 = kamp * 10
      kcps = cpsoct(koct)
      a1 oscil kamp2, kcps, 1

      out a1
    endin
    /* pitch.orc */

    /* pitch.sco */
    ; Table #1: A different sounding waveform.
    f 1 0 32768 11 7 3 .7

    ; Play Instrument #1, the audio file, for three seconds.
    i 1 0 3
    ; Play Instrument #2, the "re-synthesized" waveform, for three seconds.
    i 2 3 3
    e
    /* pitch.sco */

## Credits

Author: John ffitch
University of Bath, Codemist Ltd.
Bath, UK
April 1999

Example written by Kevin Conder.

New in Csound version 3.54

Prev | Up | Next
pinkish | Home | pitchamdf