2 files changed, 76 insertions, 3 deletions
diff --git a/build/android/pylib/perf/surface_stats_collector.py b/build/android/pylib/perf/surface_stats_collector.py
index c38b1b4..9d92b43 100644
--- a/build/android/pylib/perf/surface_stats_collector.py
+++ b/build/android/pylib/perf/surface_stats_collector.py
@@ -13,6 +13,8 @@ import threading
 _SURFACE_TEXTURE_TIMESTAMPS_MESSAGE = 'SurfaceTexture update timestamps'
 _SURFACE_TEXTURE_TIMESTAMP_RE = '\d+'
 
+_MIN_NORMALIZED_FRAME_LENGTH = 0.5
+
 
 class SurfaceStatsCollector(object):
   """Collects surface stats for a SurfaceView from the output of SurfaceFlinger.
@@ -79,8 +81,11 @@ class SurfaceStatsCollector(object):
     ]
 
   @staticmethod
-  def _GetNormalizedDeltas(data, refresh_period):
+  def _GetNormalizedDeltas(data, refresh_period, min_normalized_delta=None):
     deltas = [t2 - t1 for t1, t2 in zip(data, data[1:])]
+    if min_normalized_delta != None:
+      deltas = filter(lambda d: d / refresh_period >= min_normalized_delta,
+                      deltas)
     return (deltas, [delta / refresh_period for delta in deltas])
 
   @staticmethod
@@ -90,7 +95,13 @@ class SurfaceStatsCollector(object):
     seconds = timestamps[-1] - timestamps[0]
 
     frame_lengths, normalized_frame_lengths = \
-        SurfaceStatsCollector._GetNormalizedDeltas(timestamps, refresh_period)
+        SurfaceStatsCollector._GetNormalizedDeltas(
+            timestamps, refresh_period, _MIN_NORMALIZED_FRAME_LENGTH)
+    if len(frame_lengths) < frame_count - 1:
+      logging.warning('Skipping frame lengths that are too short.')
+      frame_count = len(frame_lengths) + 1
+    if len(frame_lengths) == 0:
+      raise Exception('No valid frames lengths found.')
     length_changes, normalized_changes = \
         SurfaceStatsCollector._GetNormalizedDeltas(
             frame_lengths, refresh_period)
@@ -101,7 +112,7 @@ class SurfaceStatsCollector(object):
     return [
         SurfaceStatsCollector.Result(
             'avg_surface_fps' + result_suffix,
-            int(round(frame_count / seconds)), 'fps'),
+            int(round((frame_count - 1) / seconds)), 'fps'),
         SurfaceStatsCollector.Result(
             'jank_count' + result_suffix, jank_count, 'janks'),
         SurfaceStatsCollector.Result(
diff --git a/build/android/pylib/perf/surface_stats_collector_unittest.py b/build/android/pylib/perf/surface_stats_collector_unittest.py
new file mode 100644
index 0000000..982b55d
--- /dev/null
+++ b/build/android/pylib/perf/surface_stats_collector_unittest.py
@@ -0,0 +1,62 @@
+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Unittests for SurfaceStatsCollector."""
+
+import unittest
+
+from surface_stats_collector import SurfaceStatsCollector
+
+class TestSurfaceStatsCollector(unittest.TestCase):
+  @staticmethod
+  def _CreateUniformTimestamps(base, num, delta):
+    return [base + i * delta for i in range(1, num + 1)]
+
+  @staticmethod
+  def _CreateDictionaryFromResults(results):
+    dictionary = {}
+    for result in results:
+      dictionary[result.name] = result
+    return dictionary
+
+  def setUp(self):
+    self.refresh_period = 0.1
+
+  def testOneFrameDelta(self):
+    timestamps = self._CreateUniformTimestamps(0, 10, self.refresh_period)
+    results = self._CreateDictionaryFromResults(
+                  SurfaceStatsCollector._CalculateResults(
+                      self.refresh_period, timestamps, ''))
+
+    self.assertEquals(results['avg_surface_fps'].value,
+                      int(round(1 / self.refresh_period)))
+    self.assertEquals(results['jank_count'].value, 0)
+    self.assertEquals(results['max_frame_delay'].value, 1)
+    self.assertEquals(len(results['frame_lengths'].value), len(timestamps) - 1)
+
+  def testAllFramesTooShort(self):
+    timestamps = self._CreateUniformTimestamps(0, 10, self.refresh_period / 100)
+    self.assertRaises(Exception,
+                      SurfaceStatsCollector._CalculateResults,
+                      [self.refresh_period, timestamps, ''])
+
+  def testSomeFramesTooShort(self):
+    timestamps = self._CreateUniformTimestamps(0, 5, self.refresh_period)
+    # The following timestamps should be skipped.
+    timestamps += self._CreateUniformTimestamps(timestamps[4],
+                                                5,
+                                                self.refresh_period / 100)
+    timestamps += self._CreateUniformTimestamps(timestamps[4],
+                                                5,
+                                                self.refresh_period)
+
+    results = self._CreateDictionaryFromResults(
+                  SurfaceStatsCollector._CalculateResults(
+                      self.refresh_period, timestamps, ''))
+
+    self.assertEquals(len(results['frame_lengths'].value), 9)
+
+
+if __name__ == '__main__':
+  unittest.main()