Spectrogram

Namespace: UTILSLIB  ·  Library: Utilities Library  ·  Source: dsp/spectrogram.h

#include <utils/spectrogram.h>

class UTILSLIB::Spectrogram

Computes time-frequency spectrograms via short-time Fourier transform with configurable window and overlap.

src/examples/ex_dsp_spectral/main.cpp

const MatrixXd spectrogram = Spectrogram::makeSpectrogram(signal.transpose(), 64); // frequency bins x samples

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Static Methods

makeSpectrogram(signal, windowSize)

Calculates the spectrogram (tf-representation) of a given signal.

Parameters:

• signal : Eigen::VectorXd input-signal to calculate spectrogram of.

• windowSize : qint32 width of the Gaussian window in samples (trades time against frequency resolution).

Returns:

• Eigen::MatrixXd — Power |STFT|^2, N/2 x N for a signal of N samples: row k is the FFT bin at k * sfreq / N Hz, column j the window centred on sample j.

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Example

• Start here: ex_dsp_spectral — Spectral and filtering tools of the dsp library on signals with known content.
• Full source: src/examples/ex_dsp_spectral/main.cpp
• Build target: ex_dsp_spectral (runs under CTest)

Used in examples

ex_disp

Disp library widgets: image map, line plot and time-frequency plot of raw data.

src/examples/ex_disp/main.cpp, line 230

//tf plot example: spectrogram of the same channel
MatrixXd dataSpectrum = Spectrogram::makeSpectrogram(dataCol, raw.info.sfreq * 0.2);
TFplot tfplot(dataSpectrum, raw.info.sfreq, 0, 100, ColorMaps::Jet, times(0, 0));

ex_tf_plot

Spectrogram of one evoked channel shown as a time-frequency plot.

src/examples/ex_tf_plot/main.cpp, line 79

//tf plot
VectorXd dataCol = p_FiffEvoked.data.row(83).transpose();
MatrixXd dataSpectrum = Spectrogram::makeSpectrogram(dataCol, p_FiffEvoked.info.sfreq * 0.1);

Authors of this file

• Christoph Dinh <christoph.dinh@mne-cpp.org>