flatEnv: Flat envelope / compressor

In tatters/soundgen: Sound Synthesis and Acoustic Analysis

Flat envelope / compressor

Description

Applies a compressor - that is, flattens the amplitude envelope of a waveform, reducing the difference in amplitude between loud and quiet sections. This is achieved by dividing the waveform by some function of its smoothed amplitude envelope (Hilbert, peak or root mean square).

Usage

flatEnv(
  x,
  samplingRate = NULL,
  scale = NULL,
  compression = 1,
  method = c("hil", "rms", "peak")[1],
  windowLength = 50,
  windowLength_points = NULL,
  killDC = FALSE,
  dynamicRange = 40,
  reportEvery = NULL,
  cores = 1,
  saveAudio = NULL,
  plot = FALSE,
  savePlots = NULL,
  col = "blue",
  width = 900,
  height = 500,
  units = "px",
  res = NA,
  ...
)

compressor(
  x,
  samplingRate = NULL,
  scale = NULL,
  compression = 1,
  method = c("hil", "rms", "peak")[1],
  windowLength = 50,
  windowLength_points = NULL,
  killDC = FALSE,
  dynamicRange = 40,
  reportEvery = NULL,
  cores = 1,
  saveAudio = NULL,
  plot = FALSE,
  savePlots = NULL,
  col = "blue",
  width = 900,
  height = 500,
  units = "px",
  res = NA,
  ...
)

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)
compression	the amount of compression to apply: 0 = none, 1 = maximum
method	hil = Hilbert envelope, rms = root mean square amplitude, peak = peak amplitude per window
windowLength	the length of smoothing window, ms
windowLength_points	the length of smoothing window, points. If specified, overrides windowLength
killDC	if TRUE, dynamically removes DC offset or similar deviations of average waveform from zero (see examples)
dynamicRange	parts of sound quieter than -dynamicRange dB will not be amplified
reportEvery	when processing multiple inputs, report estimated time left every ... iterations (NULL = default, NA = don't report)
cores	number of cores for parallel processing
saveAudio	full path to the folder in which to save the compressed sound(s)
plot	if TRUE, plots the original sound, the smoothed envelope, and the compressed sound
savePlots	full path to the folder in which to save the plots (NULL = don't save, ” = same folder as audio)
col	the color of amplitude contours
width, height, units, res	graphical parameters for saving plots passed to png
...	other graphical parameters passed to points() that control the appearance of amplitude contours, eg lwd, lty, etc.

Value

If the input is a single audio (file, Wave, or numeric vector), returns the compressed waveform as a numeric vector with the original sampling rate and scale. If the input is a folder with several audio files, returns a list of compressed waveforms, one for each file.

Examples

a = rnorm(500) * seq(1, 0, length.out = 500)
b = flatEnv(a, 1000, plot = TRUE, windowLength_points = 5)    # too short
c = flatEnv(a, 1000, plot = TRUE, windowLength_points = 450)  # too long
d = flatEnv(a, 1000, plot = TRUE, windowLength_points = 100)  # about right

## Not run: 
s = soundgen(sylLen = 1000, ampl = c(0, -40, 0), plot = TRUE)
# playme(s)
s_flat1 = flatEnv(s, 16000, dynamicRange = 60, plot = TRUE,
                  windowLength = 50, method = 'hil')
s_flat2 = flatEnv(s, 16000, dynamicRange = 60, plot = TRUE,
                  windowLength = 10, method = 'rms')
s_flat3 = flatEnv(s, 16000, dynamicRange = 60, plot = TRUE,
                  windowLength = 10, method = 'peak')
# playme(s_flat2)

# Remove DC offset
s1 = c(rep(0, 50), runif(1000, -1, 1), rep(0, 50)) +
     seq(.3, 1, length.out = 1100)
s2 = flatEnv(s1, 16000, plot = TRUE, windowLength_points = 50, killDC = FALSE)
s3 = flatEnv(s1, 16000, plot = TRUE, windowLength_points = 50, killDC = TRUE)

# Compress and save all audio files in a folder
s4 = flatEnv('~/Downloads/temp2',
             method = 'peak', compression = .5,
             saveAudio = '~/Downloads/temp2/compressed',
             savePlots = '~/Downloads/temp2/compressed',
             col = 'green', lwd = 5)
osc(s4[[1]])

## End(Not run)

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