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: 
christopher@45: from basic_functions import get_H, velocity_sequence_to_min_timespan, get_rhythm_category, upsample_velocity_sequence
christopher@45: from parameter_setter import are_parameters_valid
christopher@45: 
christopher@45: def get_syncopation(bar, parameters = None):
christopher@45: 	syncopation = None
christopher@45: 	velocitySequence = bar.get_velocity_sequence()
christopher@45: 	subdivisionSequence = bar.get_subdivision_sequence()
christopher@45: 
christopher@45: 	if get_rhythm_category(velocitySequence, subdivisionSequence) == 'poly':
christopher@45: 		print 'Warning: SG model detects polyrhythms so returning None.'
christopher@45: 	else:
christopher@45: 		#velocitySequence = velocity_sequence_to_min_timespan(velocitySequence)	# converting to the minimum time-span format
christopher@45: 
christopher@45: 		# set the defaults
christopher@45: 		Lmax  = 5
christopher@45: 		weightSequence = range(Lmax+1) # i.e. [0,1,2,3,4,5]
christopher@45: 		if parameters!= None:
christopher@45: 			if 'Lmax' in parameters:
christopher@45: 				Lmax = parameters['Lmax']				
christopher@45: 			if 'W' in parameters:
christopher@45: 				weightSequence = parameters['W']
christopher@45: 
christopher@45: 		if not are_parameters_valid(Lmax, weightSequence, subdivisionSequence):
christopher@45: 			print 'Error: the given parameters are not valid.'
christopher@45: 		else:
christopher@45: 			# generate the metrical weights of level Lmax, and upsample(stretch) the velocity sequence to match the length of H
christopher@45: 			H = get_H(weightSequence,subdivisionSequence, Lmax)
christopher@45: 			
christopher@45: 			velocitySequence = upsample_velocity_sequence(velocitySequence, len(H))
christopher@45: 
christopher@45: 			# The ave_dif_neighbours function calculates the (weighted) average of the difference between the note at a certain index and its neighbours in a certain metrical level
christopher@45: 			def ave_dif_neighbours(index, level):
christopher@45: 
christopher@45: 				averages = []
christopher@45: 				parameterGarma = 0.8
christopher@45: 				
christopher@45: 				# The findPre function is to calculate the index of the previous neighbour at a certain metrical level.
christopher@45: 				def find_pre(index, level):
christopher@45: 					preIndex = (index - 1)%len(H)	# using % is to restrict the index varies within range(0, len(H))
christopher@45: 					while(H[preIndex] > level):
christopher@45: 						preIndex = (preIndex - 1)%len(H)
christopher@45: 					#print 'preIndex', preIndex
christopher@45: 					return preIndex
christopher@45: 
christopher@45: 				# The findPost function is to calculate the index of the next neighbour at a certain metrical level.
christopher@45: 				def find_post(index, level):
christopher@45: 					postIndex = (index + 1)%len(H)
christopher@45: 					while(H[postIndex] > level):
christopher@45: 						postIndex = (postIndex + 1)%len(H)
christopher@45: 					#print 'postIndex', postIndex
christopher@45: 					return postIndex
christopher@45: 				
christopher@45: 				# The dif function is to calculate a difference level factor between two notes (at note position index1 and index 2) in velocity sequence
christopher@45: 				def dif(index1,index2):
christopher@45: 					parameterBeta = 0.5
christopher@45: 					dif_v = velocitySequence[index1]-velocitySequence[index2]
christopher@45: 					dif_h = abs(H[index1]-H[index2])
christopher@45: 					dif = dif_v*(parameterBeta*dif_h/4+1-parameterBeta)
christopher@45: 					#print 'dif', dif
christopher@45: 					return dif
christopher@45: 
christopher@45: 				# From the highest to the lowest metrical levels where the current note resides, calculate the difference between the note and its neighbours at that level
christopher@45: 				for l in range(level, max(H)+1):
christopher@45: 					ave = (parameterGarma*dif(index,find_pre(index,l))+dif(index,find_post(index,l)) )/(1+parameterGarma)
christopher@45: 					averages.append(ave)
christopher@45: 				#print 'averages', averages
christopher@45: 				return averages
christopher@45: 
christopher@45: 			# if the upsampling was successfully done
christopher@45: 			if velocitySequence != None:
christopher@45: 				syncopation = 0			
christopher@45: 				# Calculate the syncopation value for each note
christopher@45: 				for index in range(len(velocitySequence)):
christopher@45: 					if velocitySequence[index] != 0: # Onset detected
christopher@45: 						h = H[index] 
christopher@45: 						# Syncopation potential according to its metrical level, which is equal to the metrical weight
christopher@45: 						potential = 1 - pow(0.5,h)
christopher@45: 						level = h 		# Metrical weight is equal to its metrical level
christopher@45: 						syncopation += min(ave_dif_neighbours(index, level))*potential
christopher@45: 			else:
christopher@45: 				print 'Try giving a bigger Lmax so that the rhythm sequence can be measured by the matching metrical weights sequence (H).'
christopher@45: 	return syncopation