aseg1

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This function implements a simple automatic signal segmentation based on the energy (rms) track of the signal.


Usage 1
aseg1(x, 0, n, m, xmin, omax)
x
data vector (usally rms track in dB)
n
minimum length of a signal segment in frames; 0 < n < nrow(x)
m
smoothing length; 0 <= m; if m is greater than zero, the segmentation is performed on a smoothed data vector xs.
xs[i] = avr(x[i-m], .., x[i+m])
xmin
segment threshhold
omax
offset for segment center; 0 < omax
Description
  1. A segment is a continuous range of x, where all values are greater than xmin
  2. The center of a segment is a continuous range of values inside a segment, where all values are greater than xmax-omax (with: xmax is the maximum value inside the segment).


Result 1
The next (nearest) possible signal window length.

Usage 2
fft(x)
x
signal vector or matrix; if x is a matrix a spectrum of each column is computed
Result 2
A matrix y with ncol(x) columns and L+2 rows, where each column y[*,j] contains the complex spectrum of the column (channel) x[*,j]. The transformation length L is set to npow2(nrow(x)).

Usage 3
fft(x, n {, ytype, poffset, prange, aref})
x
signal vector or matrix; if x is a matrix a spectrum of each column is computed
n
desired length of analysis window;
  • If n < nrow(x), the analysis window length L is set to nrow(x), otherwise L is set to n.
  • If the analysis window length L is a power of 2 (L=2^M), the fft algorithm is used, otherwise the dft is used.
  • If L is greater than nrow(x), zero padding is applied to the signal.
ytype
select the type and format of the computed spectrum (default=0) -> see Result 3
poffset
offset in samples to the signal begin or the selected zero phase position (default=0)
poffset=0 -> phase[i] = atan2(im[i], re[i])
otherwise -> phase[i] = (atan2(im[i], re[i]) - 2*pi*i/L * poffset) % (2 * pi)
prange
selects the range of phase values (default=0)
prange=0 -> 0 <= phase[i] < 2*pi
otherwise -> -pi <= phase[i] < pi
aref
reference amplitude if the log. spectrum (ytype=4) is requested (default=1)
Result 3
A matrix y with ncol(x) columns, where each column y[*,j] contains the spectrum of the column (channel) x[*,j]. The type and the length of the spectra is selected by the argument ytype.
ytype description content of y[*,j] nrow(y)
0 complex spectrum in cartesian format { re0, im0, re1, im1, ... } L+2
1 complex spectrum in polar format { amp0, phase0, amp1, phase1, ... }
with: ampi=sqrt(rei2 + imi2),
phasei see poffset
L+2
2 amplitude spectrum { amp0, amp1, ... } L+1
3 power spectrum { amp02, amp12, ... } L+1
4 logarithmic amplitude spectrum { lev0, lev1, ... }
with: levi=20*log10(ampi/aref)
L+1

See also
ifft, dft, dct, cepstrum, lpc, complex arithmetic

<function list>




aseg1

Automatically segment a signal. Apply automatic segmentation to the vector x.

Usage:

aseg1(x, xmin, omin, omax, nmin, navr)

Parameters:
x
A data vector (e.g. an rms function).
xmin
The pause threshold.
omin
The offset for segment detection. E.g. x[i] > xmin+omin.
omax
The offset for the segment center detection. E.g. x[i] > max("segment")-omax.
nmin
The minimum segment duration in frames. A segment is assigned if the segment condition is true for at least nmin frames.
navr
The averaging length. If navr is greater than 0 then all elements x[i] are replaced by avr(x[i-navr .. i+navr]).
Result:

A matrix (or vector) y with 4 rows and one column for each detected segment. Note that all values of y are frame indices.

y[0,i] = The beginning of the segment i.

y[1,i] = The beginning of the center of the segment i.

y[2,i] = The end of the center of the segment i.

y[3,i] = The end of the segment i.

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