view cnmf.py @ 17:c01fcb752221

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"""
C-NMF method for segmentation, modified from here:

Nieto, O., Jehan, T., Convex Non-negative Matrix Factorization For Automatic
Music Structure Identification. Proc. of the 38th IEEE International Conference
on Acoustics, Speech, and Signal Processing (ICASSP). Vancouver, Canada, 2013.
"""

__author__ = "Oriol Nieto"
__copyright__ = "Copyright 2014, Music and Audio Research Lab (MARL)"
__license__ = "GPL"
__version__ = "1.0"
__email__ = "[e-mail]"

import numpy as np
import pymf

# Local stuff
from utils import SegUtil

# Algorithm params
h = 8				# Size of median filter for features in C-NMF
R = 15				# Size of the median filter for the activation matrix C-NMF
rank = 4			# Rank of decomposition for the boundaries
rank_labels = 6		# Rank of decomposition for the labels
R_labels = 6		# Size of the median filter for the labels

def cnmf(S, rank, niter=500):
	"""(Convex) Non-Negative Matrix Factorization.

	Parameters
	----------
	S: np.array(p, N)
		Features matrix. p row features and N column observations.
	rank: int
		Rank of decomposition
	niter: int
		Number of iterations to be used

	Returns
	-------
	F: np.array
		Cluster matrix (decomposed matrix)
	G: np.array
		Activation matrix (decomposed matrix)
		(s.t. S ~= F * G)
	"""
	nmf_mdl = pymf.CNMF(S, num_bases=rank)
	nmf_mdl.factorize(niter=niter)
	F = np.asarray(nmf_mdl.W)
	G = np.asarray(nmf_mdl.H)
	return F, G

def nmf(S, rank, nither=500):
	nmf_mdl = pymf.NMF(S, num_bases=rank, niter=nither)
	nmf_mdl.factorize()
	F = np.asarray(nmf_mdl.W)
	G = np.asarray(nmf_mdl.H)
	return F, G
	
	
def most_frequent(x):
	"""Returns the most frequent value in x."""
	return np.argmax(np.bincount(x))


def compute_labels(X, rank, R, bound_idxs, niter=300):
	"""Computes the labels using the bounds."""

	X = X.T
	try:
		F, G = cnmf(X, rank, niter=niter)
	except:
		return [1]

	label_frames = filter_activation_matrix(G.T, R)
	label_frames = np.asarray(label_frames, dtype=int)

	# Get labels from the label frames
	labels = []
	bound_inters = zip(bound_idxs[:-1], bound_idxs[1:])
	for bound_inter in bound_inters:
		if bound_inter[1] - bound_inter[0] <= 0:
			labels.append(np.max(label_frames) + 1)
		else:
			labels.append(most_frequent(
				label_frames[bound_inter[0]:bound_inter[1]]))

	return labels


def filter_activation_matrix(G, R):
	"""Filters the activation matrix G, and returns a flattened copy."""
	idx = np.argmax(G, axis=1)
	max_idx = np.arange(G.shape[0])
	max_idx = (max_idx, idx.flatten())
	G[:, :] = 0
	G[max_idx] = idx + 1
	G = np.sum(G, axis=1)
	G = SegUtil.median_filter(G[:, np.newaxis], R)
	return G.flatten()


def segmentation(X, rank=4, R=15, h=8, niter=300, CNMF=True):
	"""
	Gets the segmentation (boundaries and labels) from the factorization
	matrices.

	Parameters
	----------
	X: np.array()
		Features matrix (e.g. chromagram)
	rank: int
		Rank of decomposition
	R: int
		Size of the median filter for activation matrix
	niter: int
		Number of iterations for k-means
	bound_idxs : list
		Use previously found boundaries (None to detect them)
	CNMF : bool
		If True, use CNMF; otherwise use NMF
		
	Returns
	-------
	bounds_idx: np.array
		Bound indeces found
	labels: np.array
		Indeces of the labels representing the similarity between segments.
	"""

	# Filter
	X = SegUtil.median_filter(X, M=h)
	X = X.T

	# Find non filtered boundaries
	bound_idxs = None
	while True:
		if bound_idxs is None:
			try:
				if CNMF: F, G = cnmf(X, rank, niter=niter)
				else: F, G = nmf(X, rank, niter=niter)
			except:
				return np.empty(0), [1]

			# Filter G
			G = filter_activation_matrix(G.T, R)
			if bound_idxs is None:
				bound_idxs = np.where(np.diff(G) != 0)[0] + 1

		if len(np.unique(bound_idxs)) <= 2:
			rank += 1
			bound_idxs = None
		else:
			break

	return G, bound_idxs