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.
Samping 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 time series used for analysis purposes. This usually corresponds to a single column of a spectrum matrix.
Window
A vector of 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 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. 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 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.ndarrays 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-dimentional 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(音高) class(e.g., the 12 notes(音符) in the chromatic scale) at given frame/time.