sdk/platform-tools/systrace/catapult/telemetry/telemetry/internal/image_processing/frame_generator.py

   1 # Copyright 2014 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
   5 import abc
   6
   7
   8 class FrameReadError(Exception):
   9   pass
  10
  11
  12 class FrameGenerator(object):
  13   """ Defines an interface for reading input frames.
  14
  15   Attributes:
  16     _generator: A reference to the created generator.
  17   """
  18   __metaclass__ = abc.ABCMeta
  19
  20   def __init__(self):
  21     """ Initializes the FrameGenerator object. """
  22     self._generator = self._CreateGenerator()
  23
  24   @abc.abstractmethod
  25   def _CreateGenerator(self):
  26     """ Creates a new generator.
  27
  28     Implemented in derived classes.
  29
  30     Raises:
  31       FrameReadError: A error occurred in reading the frame.
  32     """
  33     raise NotImplementedError
  34
  35   @property
  36   def Generator(self):
  37     """ Returns:
  38           A reference to the created generator.
  39     """
  40     return self._generator
  41
  42   @abc.abstractproperty
  43   def CurrentTimestamp(self):
  44     """ Returns:
  45           float, The timestamp of the current frame in milliseconds.
  46     """
  47     raise NotImplementedError
  48
  49   @abc.abstractproperty
  50   def CurrentFrameNumber(self):
  51     """ Returns:
  52           int, The frame index of the current frame.
  53     """
  54     raise NotImplementedError
  55
  56   @abc.abstractproperty
  57   def Dimensions(self):
  58     """ Returns:
  59           The dimensions of the frame sequence as a tuple int (width, height).
  60           This value should be constant across frames.
  61     """
  62     raise NotImplementedError