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      1 #!/usr/bin/python
      2 
      3 # Copyright (C) 2012 The Android Open Source Project
      4 #
      5 # Licensed under the Apache License, Version 2.0 (the "License");
      6 # you may not use this file except in compliance with the License.
      7 # You may obtain a copy of the License at
      8 #
      9 #       http://www.apache.org/licenses/LICENSE-2.0
     10 #
     11 # Unless required by applicable law or agreed to in writing, software
     12 # distributed under the License is distributed on an "AS IS" BASIS,
     13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14 # See the License for the specific language governing permissions and
     15 # limitations under the License.
     16 
     17 import numpy as np
     18 import numpy.linalg
     19 import scipy as sp
     20 import scipy.fftpack
     21 import scipy.signal
     22 import math
     23 import sys
     24 from multiprocessing import Pool
     25 
     26 def convolution(data0, data1reversed, n):
     27     """calculate convolution part of data0 with data1 from pos n"""
     28     N = len(data1reversed)
     29     return np.dot(data0[n:N+n], data1reversed)
     30 
     31 
     32 def convolutionstar(args):
     33     return convolution(*args)
     34 
     35 def calc_delay(data0, data1):
     36     """Calcuate delay between two data. data0 is assumed to be recorded first,
     37        and will have longer length than data1
     38        returns delay between data0 and data1 in number of samples in data0's point of view"""
     39 
     40     len0 = len(data0)
     41     len1 = len(data1)
     42     if len1 > len0:
     43         print "data1 longer than data0"
     44         return -1
     45     searchLen = len0 - len1
     46     data1reverse = data1[::-1]
     47 
     48     # This is faster than signal.correlate as there is no need to process
     49     # full data, but still it is slow. about 18 secs for data0 of 4 secs with data1 of 1 secs
     50     print "***Caluclating delay, may take some time***"
     51     gData0 = data0
     52     gData1 = data1reverse
     53     pool = Pool(processes = 4)
     54     TASK = [(data0, data1reverse, i) for i in range(searchLen)]
     55     result = pool.map(convolutionstar, TASK)
     56 
     57     return np.argmax(result)
     58 
     59 
     60 # test code
     61 if __name__=="__main__":
     62     samplingRate = 44100
     63     durationInSec = 0.001
     64     if len(sys.argv) > 1:
     65         durationInSec = float(sys.argv[1])
     66     signalFrequency = 1000
     67     samples = float(samplingRate) * float(durationInSec)
     68     index = np.linspace(0.0, samples, num=samples, endpoint=False)
     69     time = index / samplingRate
     70     multiplier = 2.0 * np.pi * signalFrequency / float(samplingRate)
     71     data0 = np.sin(index * multiplier)
     72     DELAY = durationInSec / 2.0 * samplingRate
     73     data1 = data0[DELAY:]
     74     delay = calc_delay(data0, data1)
     75     print "calc_delay returned", delay, " while expecting ", DELAY
     76 
     77 
     78