soundgen (version 2.7.2)

flatEnv: 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,
  ...
)

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.

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.

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

if (FALSE) {
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/temp',
             method = 'peak', compression = .5,
             saveAudio = '~/Downloads/temp/compressed',
             savePlots = '~/Downloads/temp/compressed',
             col = 'green', lwd = 5)
osc(s4[[1]])
}