New rtc dump analyzing tool in Python

tools/py_event_log_analyzer/misc.py

+#  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+#
+#  Use of this source code is governed by a BSD-style license
+#  that can be found in the LICENSE file in the root of the source
+#  tree. An additional intellectual property rights grant can be found
+#  in the file PATENTS.  All contributing project authors may
+#  be found in the AUTHORS file in the root of the source tree.
+
+"""Utility functions for calculating statistics.
+"""
+
+from __future__ import division
+import collections
+import sys
+
+
+def count_reordered(sequence_numbers):
+  """Returns number of indices `i` for which
+  sequence_numbers[i] >= sequence_numbers[i+1]
+  """
+  return sum(1 for (s1, s2) in zip(sequence_numbers,
+                                   sequence_numbers[1:]) if
+             s1 >= s2)
+
+
+def ssrc_normalized_size_table(data_points):
+  """Returns mapping from a SSRC to its relative occurance proportion in
+  the data.
+  """
+  d = collections.defaultdict(int)
+  for pt in data_points:
+    d[pt.ssrc] += pt.size
+  return normalize_counter(d)
+
+
+def normalize_counter(counter):
+  """Returns a normalized (i.e. divided by total to sum up to 1) version
+  of the input dictionary `counter`. Does not modify `counter`.
+
+  """
+  total = sum(counter.values())
+  return {key: counter[key] / total for key in counter}
+
+
+def unwrap(data, mod):
+  """Returns `data` unwrapped modulo `mod`. Does not modify data.
+
+  Adds integer multiples of mod to all elements of data except the
+  first, such that all pairs of consecutive elements (a, b) satisfy
+  -mod / 2 <= b - a < mod / 2.
+
+  E.g. unwrap([0, 1, 2, 0, 1, 2, 7, 8], 3) -> [0, 1, 2, 3,
+  4, 5, 4, 5]
+
+  """
+  lst = data[:]
+  for i in range(1, len(data)):
+    lst[i] = lst[i - 1] + (lst[i] - lst[i - 1] +
+                           mod // 2) % mod - (mod // 2)
+  return lst

[kwiberg-webrtc, 2016/05/31 12:30:53]

return [data[0]] + [a + (b - a + mod // 2) % mod - mod // 2
                    for (a, b) in zip(data, data[1:])]

I think. Hopefully your unit test can check it...

[aleloi, 2016/05/31 12:40:32]

No, wont work, because 'a' comes from the original list. 'a' needs to come from
the result.

[kwiberg-webrtc, 2016/05/31 12:53:59]

Ah, right. Then it's not possible to write as just a list comprehension, since
we can't look at previous elements. Something like

  return itertools.accumulate([data[0]] + [(b - a + mod // 2) % mod - mod // 2
                                           for x in zip(data, data[1:])],
                              operator.add)

would work, if itertools.accumulate had existed in Python 2.

But let's use your version. ;-)

+
+# Python 2/3-compatible input function
+if sys.version_info[0] <= 2:
+  get_input = raw_input
+else:
+  get_input = input