comparison Syncopation models/synpy/PRS.py @ 45:6e9154fc58df

moving the code files to the synpy package directory

+'''
+Author: Chunyang Song
+Institution: Centre for Digital Music, Queen Mary University of London
+'''
+
+from basic_functions import repeat, subdivide, ceiling, velocity_sequence_to_min_timespan, get_rhythm_category
+
+def get_cost(sequence,nextSequence):
+	sequence = velocity_sequence_to_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 nextSequence[0] == 0):	# run2 prototype
+		cost = 2
+	elif 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):
+	#print 'subSequences', subSequences
+	total = 0
+	for l in range(len(subSequences)-1):
+		#print 'cost', get_cost(subSequences[l], subSequences[l+1])
+		total = total + get_cost(subSequences[l], subSequences[l+1])
+	#print 'total this level', total
+	normalised = float(total)/(len(subSequences)-1)
+	
+	return normalised
+
+def get_syncopation(bar, parameters = None):
+	syncopation = None
+
+	binarySequence = bar.get_binary_sequence()
+	subdivisionSequence = bar.get_subdivision_sequence()
+
+	# PRS does not handle polyrhythms
+	if get_rhythm_category(binarySequence, subdivisionSequence) == 'poly':
+		print 'Warning: PRS model detects polyrhythms so returning None.'
+	else:
+		syncopation = 0
+
+		# retrieve the binary sequence in the next bar
+		if bar.get_next_bar() != None:
+			nextbarBinarySequence = bar.get_next_bar().get_binary_sequence()
+		else:
+			nextbarBinarySequence = None
+
+		# numberOfSubSeqs is the number of sub-sequences at a certain metrical level, initialised to be 1 (at the bar level)
+		numberOfSubSeqs = 1	
+		for subdivisor in subdivisionSequence:
+			# numberOfSubSeqs 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
+				#print 'per level', syncopation_perlevel(subSequences)
+				syncopation += syncopation_perlevel(subSequences)	
+			else:
+				break
+
+	return syncopation