Refactor all video related processing to its own class

tools/telemetry/telemetry/core/platform/android_platform_backend.py

Index: tools/telemetry/telemetry/core/platform/android_platform_backend.py
diff --git a/tools/telemetry/telemetry/core/platform/android_platform_backend.py b/tools/telemetry/telemetry/core/platform/android_platform_backend.py
index d5c985aba87e9307dc86f07fc376afaeea104493..9a1ec607fa9599c41f4b866acb86ddd46c50a9df 100644
--- a/tools/telemetry/telemetry/core/platform/android_platform_backend.py
+++ b/tools/telemetry/telemetry/core/platform/android_platform_backend.py
@@ -3,14 +3,13 @@
 # found in the LICENSE file.
 
 import logging
-import subprocess
 import tempfile
 
 from telemetry import decorators
-from telemetry.core import bitmap
 from telemetry.core import exceptions
 from telemetry.core import platform
 from telemetry.core import util
+from telemetry.core import video
 from telemetry.core.platform import proc_supporting_platform_backend
 from telemetry.core.platform.power_monitor import android_ds2784_power_monitor
 from telemetry.core.platform.power_monitor import android_dumpsys_power_monitor
@@ -219,6 +218,7 @@ class AndroidPlatformBackend(
     return self.GetOSVersionName() >= 'K'
 
   def StartVideoCapture(self, min_bitrate_mbps):
+    """Starts the video capture at specified bitrate."""
     min_bitrate_mbps = max(min_bitrate_mbps, 0.1)
     if min_bitrate_mbps > 100:
       raise ValueError('Android video capture cannot capture at %dmbps. '
@@ -238,10 +238,10 @@ class AndroidPlatformBackend(
   def StopVideoCapture(self):
     assert self.is_video_capture_running, 'Must start video capture first'
     self._video_recorder.Stop()
-    self._video_output = self._video_recorder.Pull()
+    self._video_recorder.Pull()
     self._video_recorder = None
-    for frame in self._FramesFromMp4(self._video_output):
-      yield frame
+
+    return video.Video(self, self._video_output)
 
   def CanMonitorPower(self):
     return self._powermonitor.CanMonitorPower()
@@ -252,60 +252,6 @@ class AndroidPlatformBackend(
   def StopMonitoringPower(self):
     return self._powermonitor.StopMonitoringPower()
 
-  def _FramesFromMp4(self, mp4_file):
-    if not self.CanLaunchApplication('avconv'):
-      self.InstallApplication('avconv')
-
-    def GetDimensions(video):
-      proc = subprocess.Popen(['avconv', '-i', video], stderr=subprocess.PIPE)
-      dimensions = None
-      output = ''
-      for line in proc.stderr.readlines():
-        output += line
-        if 'Video:' in line:
-          dimensions = line.split(',')[2]
-          dimensions = map(int, dimensions.split()[0].split('x'))
-          break
-      proc.communicate()
-      assert dimensions, ('Failed to determine video dimensions. output=%s' %
-                          output)
-      return dimensions
-
-    def GetFrameTimestampMs(stderr):
-      """Returns the frame timestamp in integer milliseconds from the dump log.
-
-      The expected line format is:
-      '  dts=1.715  pts=1.715\n'
-
-      We have to be careful to only read a single timestamp per call to avoid
-      deadlock because avconv interleaves its writes to stdout and stderr.
-      """
-      while True:
-        line = ''
-        next_char = ''
-        while next_char != '\n':
-          next_char = stderr.read(1)
-          line += next_char
-        if 'pts=' in line:
-          return int(1000 * float(line.split('=')[-1]))
-
-    dimensions = GetDimensions(mp4_file)
-    frame_length = dimensions[0] * dimensions[1] * 3
-    frame_data = bytearray(frame_length)
-
-    # Use rawvideo so that we don't need any external library to parse frames.
-    proc = subprocess.Popen(['avconv', '-i', mp4_file, '-vcodec',
-                             'rawvideo', '-pix_fmt', 'rgb24', '-dump',
-                             '-loglevel', 'debug', '-f', 'rawvideo', '-'],
-                            stderr=subprocess.PIPE, stdout=subprocess.PIPE)
-    while True:
-      num_read = proc.stdout.readinto(frame_data)
-      if not num_read:
-        raise StopIteration
-      assert num_read == len(frame_data), 'Unexpected frame size: %d' % num_read
-      yield (GetFrameTimestampMs(proc.stderr),
-             bitmap.Bitmap(3, dimensions[0], dimensions[1], frame_data))
-
   def _GetFileContents(self, fname):
     if not self._can_access_protected_file_contents:
       logging.warning('%s cannot be retrieved on non-rooted device.' % fname)