# MIT License
#
# Copyright (C) 2021. Huawei Technologies Co., Ltd. All rights reserved.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import time
[docs]class FramerateException(Exception):
"""An exception raised if frame rate has increased higher than the desired threshold."""
def __str__(self):
return "The monitor has not started yet."
[docs] @classmethod
def below_threshold(cls, desired_fps, delta):
"""Generate a frame-rate exception.
Args:
desired_fps: The intended fps.
delta: The frame time taken.
Returns:
A new frame-rate exception.
"""
return cls(
f"The frame rate decreased, lower than the desired threshold, \
desired: {desired_fps} fps, actual: {round(1000 / delta, 2)} fps."
)
[docs]class FrameMonitor:
"""A tool for requiring a minimum frame rate."""
def __init__(self, desired_fps=10):
self._desired_fps = int(desired_fps)
self._maximum_frame_time_ms = round(1 / self._desired_fps, 3) * 1000
self._start_time_ms = None
def __enter__(self):
self.start()
def __exit__(self, type, value, traceback):
self.stop()
def _time_now(self):
return int(time.time() * 1000)
[docs] def start(self):
"""Starts timing the frame."""
self._start_time_ms = self._time_now()
[docs] def stop(self):
"""Ends timing the frame. Throws an exception if the frame duration is greater than
desired fps.
"""
if self._start_time_ms is None:
print("The monitor has not started yet.")
return -1
now = self._time_now()
delta = now - self._start_time_ms
actual_fps = round(1000 / delta, 2)
if actual_fps < self._desired_fps:
raise FramerateException.below_threshold(self._desired_fps, delta)
return actual_fps