I25 viterbi test

tests/scripts/v27_enc.py

@@ -0,0 +1,128 @@
+'''
+Copyright (C) 2016 Swift Navigation Inc.
+Contact: Dmitry Tatarinov <[email protected]>
+
+This source is subject to the license found in the file 'LICENSE' which must
+be be distributed together with this source. All other rights reserved.
+
+THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
+EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
+
+'''
+
+'''
+The Python script performs convolutional encoding of a file for Viterbi
+decoder testing purposes.
+
+USAGE: 
+  python v27_enc.py <input_file_name> <output_file_name>
+
+OUTPUT:
+  Symbol file <output_file_name> which has encoded data, each byte is
+  represented as 0xff for '1' and 0x00 for '0' parity bits.
+'''
+
+import struct
+import os
+import sys
+
+G1 = 0171 #generator polinomial for p1
+G2 = 0133 #generator polinomial for p2
+
+def parity(st):
+  return (0x6996 >> ((st ^ (st >> 4)) & 15)) & 1
+
+state = 0
+
+if len(sys.argv) < 3:
+  print 'Not enough input data. Usage: v27_enc.py <input_file> <output_file>'
+  exit()
+else:
+  f_in_name = str(sys.argv[1])
+  f_out_name = str(sys.argv[2])
+
+f_out_hard = open(f_out_name,'wb')
+f_in = open(f_in_name,'rb')
+
+f_in_size = os.path.getsize(f_in_name)
+
+byte = 0
+
+pre =  [0,0,0,0]
+post = [0,0,0,0]
+
+# 2 bits delay to have data be byte aligned
+j = 3
+while j >= 0:
+  f_out_hard.write(chr(0))
+  j -= 1
+
+#encode prefix first
+for b in pre:
+  j = 7
+  while j >= 0:
+    state = (((b >> j) & 1) << 6) | (state >> 1)
+    p1 = parity(state & G1)
+    p2 = parity(state & G2)
+    #here is output SN-like for Viterbi decoder testing 
+    if p1 == 1:
+      f_out_hard.write(chr(0xff))
+    else:
+      f_out_hard.write(chr(0))
+
+    if p2 == 1:
+      f_out_hard.write(chr(0xff))
+    else:
+      f_out_hard.write(chr(0))
+
+    j -= 1
+
+#now encode data from file
+with open(f_in_name,'rb') as f_in:
+  while f_in_size:
+    byte = struct.unpack('B',f_in.read(1))[0] #read byte from input file
+
+    j = 7
+    while j >= 0: #for each bit in the byte
+      state = (((byte >> j) & 1) << 6) | (state >> 1)
+      p1 = parity(state & G1) #calculate parity
+      p2 = parity(state & G2)
+
+      #here is output SN-like for Viterbi decoder testing 
+      if p1 == 1:
+        f_out_hard.write(chr(0xff))
+      else:
+        f_out_hard.write(chr(0))
+
+      if p2 == 1:
+        f_out_hard.write(chr(0xff))
+      else:
+        f_out_hard.write(chr(0))
+
+      j -= 1
+
+    f_in_size -= 1;
+
+#encode postfix
+for b in post:
+  j = 7
+  while j >= 0:
+    state = (((b >> j) & 1) << 6) | (state >> 1)
+    p1 = parity(state & G1)
+    p2 = parity(state & G2)
+    #here is output SN-like for Viterbi decoder testing 
+    if p1 == 1:
+      f_out_hard.write(chr(0xff))
+    else:
+      f_out_hard.write(chr(0))
+
+    if p2 == 1:
+      f_out_hard.write(chr(0xff))
+    else:
+      f_out_hard.write(chr(0))
+
+    j -= 1
+
+f_out_hard.close()
+f_in.close()