getPitchZc: Zero-crossing rate

In soundgen: Sound Synthesis and Acoustic Analysis

Zero-crossing rate

Description

A less precise, but very quick method of pitch tracking based on measuring zero-crossing rate in low-pass-filtered audio. Recommended for processing long recordings with typical pitch values well below the first formant frequency, such as speech. Calling this function is considerably faster than using the same pitch-tracking method in analyze. Note that, unlike analyze(), it returns the times of individual zero crossings (hopefully corresponding to glottal cycles) instead of pitch values at fixed time intervals.

Usage

getPitchZc(
  x,
  samplingRate = NULL,
  scale = NULL,
  from = NULL,
  to = NULL,
  pitchFloor = 50,
  pitchCeiling = 400,
  zcThres = 0.1,
  zcWin = 5,
  silence = 0.04,
  envWin = 5,
  summaryFun = c("mean", "sd"),
  reportEvery = NULL
)

Arguments

x	path to a folder, one or more wav or mp3 files c('file1.wav', 'file2.mp3'), Wave object, numeric vector, or a list of Wave objects or numeric vectors
samplingRate	sampling rate of x (only needed if x is a numeric vector)
scale	maximum possible amplitude of input used for normalization of input vector (only needed if x is a numeric vector)
from, to	if NULL (default), analyzes the whole sound, otherwise from...to (s)
pitchFloor, pitchCeiling	absolute bounds for pitch candidates (Hz)
zcThres	pitch candidates with certainty below this value are treated as noise and set to NA (0 = anything goes, 1 = pitch must be perfectly stable over zcWin)
zcWin	certainty in pitch candidates depends on how stable pitch is over zcWin glottal cycles (odd integer > 3)
silence	minimum root mean square (RMS) amplitude, below which pitch candidates are set to NA (NULL = don't consider RMS amplitude)
envWin	window length for calculating RMS envelope, ms
summaryFun	functions used to summarize each acoustic characteristic; see analyze
reportEvery	when processing multiple inputs, report estimated time left every ... iterations (NULL = default, NA = don't report)

Details

Algorithm: the audio is bandpass-filtered from pitchFloor to pitchCeiling, and the timing of all zero crossings is saved. This is not enough, however, because unvoiced sounds like white noise also have plenty of zero crossings. Accordingly, an attempt is made to detect voiced segments (or steady musical tones, etc.) by looking for stable regions, with several zero-crossings at relatively regular intervals (see parameters zcThres and zcWin). Very quiet parts of audio are also treated as not having a pitch.

Value

Returns a dataframe containing

time

time stamps of all zero crossings except the last one, after bandpass-filtering

pitch

pitch calculated from the time between consecutive zero crossings

cert

certainty in each pitch candidate calculated from local pitch stability, 0 to 1

See Also

analyze

Examples

data(sheep, package = 'seewave')
# spectrogram(sheep)
zc = getPitchZc(sheep, pitchCeiling = 250)
plot(zc$detailed[, c('time', 'pitch')], type = 'b')

# Convert to a standard pitch contour sampled at regular time intervals:
pitch = getSmoothContour(
  anchors = data.frame(time = zc$detailed$time, value = zc$detailed$pitch),
  len = 1000, NA_to_zero = FALSE, discontThres = 0)
spectrogram(sheep, extraContour = pitch, ylim = c(0, 2))

## Not run: 
# process all files in a folder
zc = getPitchZc('~/Downloads/temp')
zc$summary

## End(Not run)

soundgen documentation built on Sept. 12, 2024, 6:29 a.m.