SuperCollider CLASSES (extension)

KeyClarity
ExtensionExtension

Running score of maximum correlation of chromagram with key profiles
Inherits from: UGen : AbstractFunction : Object

Description

A (12TET major/minor) key tracker based on a pitch class profile of energy across FFT bins and matching this to templates for major and minor scales in all transpositions. It assumes a 440 Hz concert A reference. Output is the strength of the match to scales, e.g. maximal correlation with key profiles. Provides a measure of the level of key clarity, e.g. unambiguous key.

Class Methods

*kr (chain, keydecay: 2, chromaleak: 0.5)

Arguments:

chain

[fft] Audio input to track. This must have been pre-analysed by a 4096 size FFT. No other FFT sizes are valid except as noted below.

// With standard hop of half FFT size = 2048 samples
b = Buffer.alloc(s,4096,1); // for sampling rates 44100 and 48000
//b = Buffer.alloc(s,8192,1); // for sampling rates 88200 and 96000
keydecay

[sk] Number of seconds for the influence of a window on the final key decision to decay by 40dB (to 0.01 its original value).

chromaleak

[sk] Each frame, the chroma values are set to the previous value multiplied by the chromadecay. 0.0 will start each frame afresh with no memory.

Inherited class methods

Instance Methods

Inherited instance methods

Examples

d = Buffer.read(s, "/data/audio/mirdata/pixiesivebeentired.wav")

d = Buffer.read(s,"/data/audio/mirdata/Beethoven8mvt4.wav")

b = Buffer.alloc(s, 4096, 1); // for sampling rates 44100 and 48000

(
{
var in, fft, resample;
var key, transientdetection;

in = PlayBuf.ar(1, d, BufRateScale.kr(d), 1, 0, 1);

fft = FFT(b, in);

key=KeyClarity.kr(fft, 2.0, 0.5);

key.poll;

Out.ar(0,Pan2.ar(in));
}.play
)