christopher@45: '''
christopher@45: Author: Chunyang Song
christopher@45: Institution: Centre for Digital Music, Queen Mary University of London
christopher@45: '''
christopher@45: 
christopher@45: from basic_functions import repeat, subdivide, ceiling, velocity_sequence_to_min_timespan, get_rhythm_category
christopher@45: 
christopher@45: def get_cost(sequence,nextSequence):
christopher@45: 	sequence = velocity_sequence_to_min_timespan(sequence)					# converting to the minimum time-span format
christopher@45: 	
christopher@45: 	if sequence[1:] == repeat([0],len(sequence)-1):		# null prototype
christopher@45: 		cost = 0
christopher@45: 	elif sequence == repeat([1],len(sequence)):			# filled prototype
christopher@45: 		cost = 1
christopher@45: 	elif sequence[0] == 1 and sequence[-1] == 0:			# run1 prototype
christopher@45: 		cost = 2
christopher@45: 	elif sequence[0] == 1 and (nextSequence == None or nextSequence[0] == 0):	# run2 prototype
christopher@45: 		cost = 2
christopher@45: 	elif sequence[-1] == 1 and nextSequence != None and nextSequence[0] == 1:		# upbeat prototype
christopher@45: 		cost = 3
christopher@45: 	elif sequence[0] == 0:							# syncopated prototype
christopher@45: 		cost = 5
christopher@45: 
christopher@45: 	return cost
christopher@45: 
christopher@45: # This function calculates the syncopation value (cost) for the sequence with the postbar_seq for a certain level. 
christopher@45: def syncopation_perlevel(subSequences):
christopher@45: 	#print 'subSequences', subSequences
christopher@45: 	total = 0
christopher@45: 	for l in range(len(subSequences)-1):
christopher@45: 		#print 'cost', get_cost(subSequences[l], subSequences[l+1])
christopher@45: 		total = total + get_cost(subSequences[l], subSequences[l+1])
christopher@45: 	#print 'total this level', total
christopher@45: 	normalised = float(total)/(len(subSequences)-1)
christopher@45: 	
christopher@45: 	return normalised
christopher@45: 
christopher@45: def get_syncopation(bar, parameters = None):
christopher@45: 	syncopation = None
christopher@45: 
christopher@50: 	binarySequence = velocity_sequence_to_min_timespan(bar.get_binary_sequence())
christopher@45: 	subdivisionSequence = bar.get_subdivision_sequence()
christopher@45: 
christopher@45: 	# PRS does not handle polyrhythms
christopher@45: 	if get_rhythm_category(binarySequence, subdivisionSequence) == 'poly':
christopher@45: 		print 'Warning: PRS model detects polyrhythms so returning None.'
christopher@50: 	elif bar.is_empty():
christopher@50: 		print 'Warning: PRS model detects empty bar so returning None.'
christopher@45: 	else:
christopher@45: 		syncopation = 0
christopher@45: 
christopher@45: 		# retrieve the binary sequence in the next bar
christopher@45: 		if bar.get_next_bar() != None:
christopher@45: 			nextbarBinarySequence = bar.get_next_bar().get_binary_sequence()
christopher@45: 		else:
christopher@45: 			nextbarBinarySequence = None
christopher@45: 
christopher@45: 		# numberOfSubSeqs is the number of sub-sequences at a certain metrical level, initialised to be 1 (at the bar level)
christopher@45: 		numberOfSubSeqs = 1	
christopher@45: 		for subdivisor in subdivisionSequence:
christopher@45: 			# numberOfSubSeqs is product of all the subdivisors up to the current level
christopher@45: 			numberOfSubSeqs = numberOfSubSeqs * subdivisor
christopher@45: 			
christopher@45: 			# recursion stops when the length of sub-sequence is less than 2
christopher@45: 			if len(binarySequence)/numberOfSubSeqs >= 2:		
christopher@45: 				# generate sub-sequences and append the next bar sequence
christopher@45: 				subSequences = subdivide(ceiling(binarySequence), numberOfSubSeqs)	
christopher@45: 				subSequences.append(nextbarBinarySequence)
christopher@45: 				# adding syncopation at each metrical level to the total syncopation
christopher@45: 				#print 'per level', syncopation_perlevel(subSequences)
christopher@45: 				syncopation += syncopation_perlevel(subSequences)	
christopher@45: 			else:
christopher@45: 				break
christopher@45: 
christopher@45: 	return syncopation