Copy

Analysis

Tempo and beats, spectrum, and silence.

On this page

Tempo and beats, spectrum, and silence.

audioBpm

Detect the tempo of audio and where its beats fall

audioBpm( audio, minBpm=60, maxBpm=200 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`minBpm`	double	`60`	Lowest tempo to consider. Defaults to 60.
`maxBpm`	double	`200`	Highest tempo to consider. Defaults to 200.

Returns A struct with bpm (0 if there is no clear pulse), confidence (0 to 1) and beats, the beat times in seconds.

Get the level of audio in log spaced frequency bands, in dB

audioSpectrum( audio, bands=16, minHz=40, maxHz=16000, start=0, seconds=0 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`bands`	integer	`16`	How many bands. Defaults to 16.
`minHz`	double	`40`	Lower edge of the first band. Defaults to 40.
`maxHz`	double	`16000`	Upper edge of the last band, capped at half the sample rate. Defaults to 16000.
`start`	double	`0`	Start in seconds. Defaults to 0.
`seconds`	double	`0`	Length to analyse in seconds, 0 for the rest. Defaults to 0.

Returns An array of band levels in dB, lowest frequency first. -120 means nothing.

Get the band levels of audio over time, for drawing or analysis

audioSpectrogram( audio, bands=16, frames=64, minHz=40, maxHz=16000 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`bands`	integer	`16`	How many bands. Defaults to 16.
`frames`	integer	`64`	How many time slices. Defaults to 64.
`minHz`	double	`40`	Lower edge of the first band. Defaults to 40.
`maxHz`	double	`16000`	Upper edge of the last band. Defaults to 16000.

Returns An array of frames, each an array of band levels in dB.

Get the frequency spectrum of one window of audio

audioFft( audio, size=2048, start=0 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`size`	integer	`2048`	FFT size, a power of two. Defaults to 2048.
`start`	double	`0`	Where the window starts, in seconds. Defaults to 0.

Returns A struct with frequencies (Hz) and magnitudes (1 for a full scale sine), arrays of size/2+1 values.

Find the silent stretches of audio

audioDetectSilence( audio, thresholdDb=-50, minSeconds=0.3 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`thresholdDb`	double	`-50`	Level below which audio counts as silent, in dB. Defaults to -50.
`minSeconds`	double	`0.3`	The shortest silence to report. Defaults to 0.3.

Returns An array of structs with start, end and duration in seconds.

Cut the silence off the start and the end of audio

audioTrimSilence( audio, thresholdDb=-50, pad=0 )

Argument	Type	Default
`audio`	any	required	The audio buffer.
`thresholdDb`	double	`-50`	Level below which audio counts as silent, in dB. Defaults to -50.
`pad`	double	`0`	Seconds of silence to keep on each side. Defaults to 0.

Returns A new audio buffer.