soundgen (version 2.1.0)

downsample: Downsample a vector

Description

Internal soundgen function

Usage

downsample(x, f, maxDec = 100)

Arguments

x

numeric vector of real numbers on any scale

f

decimation factor (1 = no effect, 1.1 = 10% shorter, 2 = half the original length)

maxDec

don't low-pass filter for f greater than this value, just decimate directly

Details

Takes a numeric vector and downsamples it to the required sampling rate by applying a low-pass filter and then decimating. If the new sampling rate is higher than the original, it does nothing.

Examples

# NOT RUN {
silence = rep(0, 10)
samplingRate = 1000
fr = seq(100, 300, length.out = 400)
x = c(silence, sin(cumsum(fr) * 2 * pi / samplingRate), silence)
spectrogram(x, samplingRate)
x1 = soundgen:::downsample(x, f = 2.5)
spectrogram(x1, samplingRate)  # no aliasing

# cf. simple decimation w/o low-pass filtering
x3 = x[seq(1, length(x), length.out = length(x) / 2.5)]
spectrogram(x3, samplingRate)  # major aliasing

# low-pass is not applied for extreme decimation
soundgen:::downsample(x, f = 120)
# }