csong@0: '''
csong@0: Author: Chunyang Song
csong@0: Institution: Centre for Digital Music, Queen Mary University of London
csong@0: '''
csong@0: 
csong@1: from basic_functions import repeat, subdivide, ceiling, get_min_timeSpan
csong@1: 
csong@1: def get_cost(seq,next_seq):
csong@1: 	seq = get_min_timeSpan(seq)					# converting to the minimum time-span format
csong@1: 	
csong@1: 	if seq[1:] == repeat([0],len(seq)-1):		# null prototype
csong@1: 		cost = 0
csong@1: 	elif seq == repeat([1],len(seq)):			# filled prototype
csong@1: 		cost = 1
csong@1: 	elif seq[0] == 1 and seq[-1] == 0:			# run1 prototype
csong@1: 		cost = 2
csong@1: 	elif seq[0] == 1 and (next_seq == None or next_seq[0] == 0):	# run2 prototype
csong@1: 		cost = 2
csong@1: 	elif seq[0] == 1 and seq[-1] == 1 and next_seq != None and next_seq[0] == 1:		# upbeat prototype
csong@1: 		cost = 3
csong@1: 	elif seq[0] == 0:							# syncopated prototype
csong@1: 		cost = 5
csong@1: 
csong@1: 	return cost
csong@1: 
csong@1: # This function calculates the syncopation value (cost) for the sequence with the postbar_seq for a certain level. 
csong@1: def syncopation_perlevel(sub_seqs, num_subs):
csong@1: 	total = 0
csong@1: 	for l in range(num_subs):
csong@1: 		total = total + get_cost(sub_seqs[l], sub_seqs[l+1])
csong@1: 	normalised = float(total)/num_subs
csong@1: 	
csong@1: 	return normalised
csong@1: 
csong@1: # This function calculates the overall syncopation value for a bar of sequence..
csong@1: def get_syncopation(seq,subdivision_seq, postbar_seq, rhythm_category):
csong@1: 	syncopation = None
csong@1: 	if rhythm_category == 'poly':
csong@1: 		print 'Error: PRS model cannot deal with polyrhythms.'
csong@0: 	else:
csong@1: 		syncopation = 0
csong@0: 
csong@1: 		current_num_subs = 1	# the initial number of sub-sequences at a certain metrical level
csong@1: 		for subdivisor in subdivision_seq:
csong@1: 			# the number of sub-sequence at the current level is product of all the subdivisors up to the current level
csong@1: 			current_num_subs = current_num_subs * subdivisor
csong@1: 			# recursion stops when the length of sub-sequence is less than 2
csong@1: 			if len(seq)/current_num_subs >= 2:		
csong@1: 				# generate sub-sequences and append the next bar sequence
csong@1: 				sub_seqs = subdivide(ceiling(seq), current_num_subs)	
csong@1: 				sub_seqs.append(postbar_seq)
csong@1: 				# adding syncopation at each metrical level to the total syncopation
csong@1: 				syncopation += syncopation_perlevel(sub_seqs, current_num_subs)	
csong@1: 			else:
csong@1: 				break
csong@0: 
csong@1: 	return syncopation