timeStretch {soundgen}

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

See Also

shiftPitch

Examples

data(sheep, package = 'seewave')  # import a recording from seewave
# playme(sheep)
# spectrogram(sheep)
s1 = timeStretch(sheep, stretch = c(1, 3))
# playme(s1, [e-mail])
# spectrogram(s1, [e-mail])

# 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, [e-mail])
# spectrogram(s2, [e-mail])
# 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