Glossary
========
.. glossary::
time series
Typically an audio signal, denoted by `y`, and represented as a
one-dimensional *numpy.ndarray* of floating-point values. `y[t]`
corresponds to amplitude of the waveform at sample `t`.
sampling rate
The (positive integer) number of samples per second of a time series.
This is denoted by an integer variable `sr`.
frame
A short slice of a :term:`time series` used for analysis purposes. This
usually corresponds to a single column of a spectrogram matrix.
window
A vector or function used to weight samples within a frame when computing
a spectrogram.
frame length
The (positive integer) number of samples in an analysis window (or
:term:`frame`).
This is denoted by an integer variable `n_fft`.
hop length
The number of samples between successive frames, e.g., the columns
of a spectrogram. This is denoted as a positive integer `hop_length`.
window length
The length (width) of the window function (e.g., Hann window). Note that this
can be smaller than the :term:`frame length` used in a short-time Fourier
transform. Typically denoted as a positive integer variable `win_length`.
spectrogram
A matrix `S` where the rows index frequency bins, and the columns index
frames (time). Spectrograms can be either real-valued or complex-valued. By
convention, real-valued spectrograms are denoted as *numpy.ndarray*\ s `S`,
while complex-valued STFT matrices are denoted as `D`.
onset (strength) envelope
An onset envelope `onset_env[t]` measures the strength of note onsets at
frame `t`. Typically stored as a one-dimensional *numpy.ndarray* of
floating-point values `onset_envelope`.
chroma
Also known as pitch class profile (PCP). Chroma representations measure the
amount of relative energy in each pitch class (e.g., the 12 notes in the
chromatic scale) at a given frame/time.