annotate Syncopation models/PRS.py @ 19:9030967a05f8

Refactored parameter_setter, basic_functions. Halfway fixing parameter argument in LHL model.

'''
Author: Chunyang Song
Institution: Centre for Digital Music, Queen Mary University of London
'''

from basic_functions import repeat, subdivide, ceiling, get_min_timeSpan, get_rhythm_category

def get_cost(sequence,nextSequence):
	sequence = get_min_timeSpan(sequence)					# converting to the minimum time-span format
	
	if sequence[1:] == repeat([0],len(sequence)-1):		# null prototype
		cost = 0
	elif sequence == repeat([1],len(sequence)):			# filled prototype
		cost = 1
	elif sequence[0] == 1 and sequence[-1] == 0:			# run1 prototype
		cost = 2
	elif sequence[0] == 1 and (nextSequence == None or nenextSequencext_seq[0] == 0):	# run2 prototype
		cost = 2
	elif sequence[0] == 1 and sequence[-1] == 1 and nextSequence != None and nextSequence[0] == 1:		# upbeat prototype
		cost = 3
	elif sequence[0] == 0:							# syncopated prototype
		cost = 5

	return cost

# This function calculates the syncopation value (cost) for the sequence with the postbar_seq for a certain level. 
def syncopation_perlevel(subSequences):
	total = 0
	for l in range(len(subSequences)-1):
		total = total + get_cost(subSequences[l], subSequences[l+1])
	normalised = float(total)/(len(subSequences)-1)
	
	return normalised

#def get_syncopation(seq,subdivision_seq, postbar_seq, rhythm_category):
def get_syncopation(bar, parameters = None):
	'''
	The get_syncopation function calculates the overall syncopation value for a bar of sequence.
	'''
	syncopation = None

	binarySequence = bar.get_binary_sequence()
	subdivisionSequence = bar.get_subdivision_sequence()

	if get_rhythm_category(binarySequence, subdivisionSequence) == 'poly':
		print 'Warning: PRS model detects polyrhythms so returning None.'
	else:
		syncopation = 0

		if bar.get_next_bar() != None:
			nextbarBinarySequence = bar.get_next_bar().get_binary_sequence()
		else:
			nextbarBinarySequence = None

		# the initial number of sub-sequences at a certain metrical level
		numberOfSubSeqs = 1	
		for subdivisor in subdivisionSequence:
			# the number of sub-sequence at the current level is product of all the subdivisors up to the current level
			numberOfSubSeqs = numberOfSubSeqs * subdivisor
			# recursion stops when the length of sub-sequence is less than 2
			if len(binarySequence)/numberOfSubSeqs >= 2:		
				# generate sub-sequences and append the next bar sequence
				subSequences = subdivide(ceiling(binarySequence), numberOfSubSeqs)	
				subSequences.append(nextbarBinarySequence)
				# adding syncopation at each metrical level to the total syncopation
				syncopation += syncopation_perlevel(subSequences)	
			else:
				break

	return syncopation