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librosa.feature.chroma_cqt

librosa.feature.chroma_cqt(*, y=None, sr=22050, C=None, hop_length=512, fmin=None, norm=inf, threshold=0.0, tuning=None, n_chroma=12, n_octaves=7, window=None, bins_per_octave=36, cqt_mode='full')

Constant-Q chromagram

Parameters:

ynp.ndarray [shape=(…, n,)]

audio time series. Multi-channel is supported.

srnumber > 0

sampling rate of y

Cnp.ndarray [shape=(…, d, t)] [Optional]

a pre-computed constant-Q spectrogram

hop_lengthint > 0

number of samples between successive chroma frames

fminfloat > 0

minimum frequency to analyze in the CQT. Default: C1 ~= 32.7 Hz

normint > 0, +-np.inf, or None

Column-wise normalization of the chromagram.

thresholdfloat

Pre-normalization energy threshold. Values below the threshold are discarded, resulting in a sparse chromagram.

tuningfloat [scalar] or None.

Deviation (in fractions of a CQT bin) from A440 tuning

n_chromaint > 0

Number of chroma bins to produce

n_octavesint > 0

Number of octaves to analyze above fmin

windowNone or np.ndarray

Optional window parameter to filters.cq_to_chroma

bins_per_octaveint > 0, optional

Number of bins per octave in the CQT. Must be an integer multiple of n_chroma. Default: 36 (3 bins per semitone) If None, it will match n_chroma.

cqt_mode[‘full’, ‘hybrid’]

Constant-Q transform mode

Returns:

chromagramnp.ndarray [shape=(…, n_chroma, t)]

The output chromagram

See also

librosa.util.normalize

librosa.cqt

librosa.hybrid_cqt

chroma_stft

Examples

Compare a long-window STFT chromagram to the CQT chromagram

>>> y, sr = librosa.load(librosa.ex('nutcracker'), duration=15)
>>> chroma_stft = librosa.feature.chroma_stft(y=y, sr=sr,
...                                           n_chroma=12, n_fft=4096)
>>> chroma_cq = librosa.feature.chroma_cqt(y=y, sr=sr)

>>> import matplotlib.pyplot as plt
>>> fig, ax = plt.subplots(nrows=2, sharex=True, sharey=True)
>>> librosa.display.specshow(chroma_stft, y_axis='chroma', x_axis='time', ax=ax[0])
>>> ax[0].set(title='chroma_stft')
>>> ax[0].label_outer()
>>> img = librosa.display.specshow(chroma_cq, y_axis='chroma', x_axis='time', ax=ax[1])
>>> ax[1].set(title='chroma_cqt')
>>> fig.colorbar(img, ax=ax)