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      1 # Copyright 2013 The Chromium Authors. All rights reserved.
      2 # Use of this source code is governed by a BSD-style license that can be
      3 # found in the LICENSE file.
      4 import logging
      5 import os
      6 
      7 from metrics import Metric
      8 
      9 class MediaMetric(Metric):
     10   """MediaMetric class injects and calls JS responsible for recording metrics.
     11 
     12   Default media metrics are collected for every media element in the page,
     13   such as decoded_frame_count, dropped_frame_count, decoded_video_bytes, and
     14   decoded_audio_bytes.
     15   """
     16   def __init__(self, tab):
     17     super(MediaMetric, self).__init__()
     18     with open(os.path.join(os.path.dirname(__file__), 'media.js')) as f:
     19       js = f.read()
     20       tab.ExecuteJavaScript(js)
     21     self._results = None
     22 
     23   def Start(self, page, tab):
     24     """Create the media metrics for all media elements in the document."""
     25     tab.ExecuteJavaScript('window.__createMediaMetricsForDocument()')
     26 
     27   def Stop(self, page, tab):
     28     self._results = tab.EvaluateJavaScript('window.__getAllMetrics()')
     29 
     30   def AddResults(self, tab, results):
     31     """Reports all recorded metrics as Telemetry perf results."""
     32     assert self._results
     33     for media_metric in self._results:
     34       self._AddResultsForMediaElement(media_metric, results)
     35 
     36   def _AddResultsForMediaElement(self, media_metric, results):
     37     """Reports metrics for one media element.
     38 
     39     Media metrics contain an ID identifying the media element and values:
     40     media_metric = {
     41       'id': 'video_1',
     42       'metrics': {
     43           'time_to_play': 120,
     44           'decoded_bytes': 13233,
     45           ...
     46       }
     47     }
     48     """
     49     def AddOneResult(metric, unit):
     50       metrics = media_metric['metrics']
     51       for m in metrics:
     52         if m.startswith(metric):
     53           special_label = m[len(metric):]
     54           results.Add(trace + special_label, unit, str(metrics[m]),
     55                       chart_name=metric, data_type='default')
     56 
     57     trace = media_metric['id']
     58     if not trace:
     59       logging.error('Metrics ID is missing in results.')
     60       return
     61     AddOneResult('decoded_audio_bytes', 'bytes')
     62     AddOneResult('decoded_video_bytes', 'bytes')
     63     AddOneResult('decoded_frame_count', 'frames')
     64     AddOneResult('dropped_frame_count', 'frames')
     65     AddOneResult('playback_time', 'sec')
     66     AddOneResult('seek', 'sec')
     67     AddOneResult('time_to_play', 'sec')
     68 
     69