timeStretch: Time stretch
In tatters/soundgen: Sound Synthesis and Acoustic Analysis

timeStretch

R Documentation

Time stretch

Description

Dynamically time-stretches a sound without preserving its pitch or formants, as if gradually changing playback speed. Algorithm: the audio is resampled at time-varying steps. This is about 100 times faster than time-stretching with a phase vocoder in shiftPitch, but pitch and formants cannot be preserved, and large stretch factors may cause artifacts due to aliasing.

Usage

timeStretch(
  x,
  stretch = 1,
  samplingRate = NULL,
  precision = 1000,
  play = FALSE,
  saveAudio = NULL,
  reportEvery = NULL,
  cores = 1
)

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
`stretch`	1 = no change, >1 = longer, <1 = shorter. Single value, vector, or anchor format (see `soundgen`)
`samplingRate`	sampling rate of `x` (only needed if `x` is a numeric vector)
`precision`	the number of points used for estimating the duration of output (more = better, but slower)
`play`	if TRUE, plays the synthesized sound using the default player on your system. If character, passed to `play` as the name of player to use, eg "aplay", "play", "vlc", etc. In case of errors, try setting another default player for `play`
`saveAudio`	full path to the folder in which to save audio files (one per detected syllable)
`reportEvery`	when processing multiple inputs, report estimated time left every ... iterations (NULL = default, NA = don't report)
`cores`	number of cores for parallel processing

Examples

data(sheep, package = 'seewave')  # import a recording from seewave
# playme(sheep)
# spectrogram(sheep)
s1 = timeStretch(sheep, stretch = c(1, 3))
# playme(s1, sheep@samp.rate)
# spectrogram(s1, sheep@samp.rate)

# compare to a similar effect achieved with a phase vocoder in pitchShift():
s2 = shiftPitch(
  sheep,
  timeStretch = c(1, 3),  # from 1 (original) to mult
  multPitch = c(1, 1/3),  # also drop pitch
  multFormants = c(1, 1/3)  # also drop formants (by the same proportion)
)
# playme(s2, sheep@samp.rate)
# spectrogram(s2, sheep@samp.rate)
# NB: because the two algorithms calculate transitions between stretch
# factors in different ways, the duration is not identical, even though the
# range of pitch change is the same

tatters/soundgen documentation built on Aug. 22, 2023, 4:24 p.m.