A simple pitch/roll/yaw rates calculator based on DVR frames count, useful for when you cannot record blackbox logs.

rates_from_dvr.py

#! /usr/bin/env python
"""
A simple pitch/roll/yaw rates calculator based on DVR frames count, useful for when you cannot record blackbox logs.

Usage: record a DVR of your aircraft doing a few flips/rolls in each axis, and then count how many frames it took to execute the maneuver and turn back level/straight.
"""

from math import ceil
from os.path import isfile
from statistics import mean

try:
    from pymediainfo import MediaInfo
except ImportError:
    try:
        import cv2
    except ImportError:
        pass


"""
Calculate a maneuver's durations based on how many video frames it took to complete.
"""
def calc_time(avg_frames_count, video_fps):
    return avg_frames_count / video_fps


"""
Convert a maneuver's duration in degrees per seconds, rounding up to the nearest ten (ex.: 467 -> 470).
"""
def calc_dps_round_to_10th(maneuver_time):
    return ceil((360 / maneuver_time) / 10.0) * 10


"""
Get the path of the DVR recording.
"""
def get_dvr_path():
    dvr_path = ""
    while dvr_path == "" or not isfile(dvr_path):
        dvr_path = input("Specify DVR file path: ")
    return dvr_path


"""
Extract the FPS value from the DVR recording.

This will be done automatically if the needed dependencies are found, else the user will have to enter this value manually.
"""
def get_dvr_fps():
    try:
        if MediaInfo:
            media_info = MediaInfo.parse(get_dvr_path())
            for track in media_info.tracks:
                if track.track_type == 'Video':
                    return float(track.frame_rate)
    except NameError:
        pass

    try:
        if cv2:
            return cv2.VideoCapture(get_dvr_path()).get(cv2.CAP_PROP_FPS)
    except NameError:
        pass

    print("*** Pymediainfo or OpenCV not found, DVR's FPS will need to be specified manually.")
    return float(input("Specify DVR's FPS: "))


if __name__ == '__main__':
    fps = get_dvr_fps()
    print("DVR's FPS: {}".format(round(fps, 3)))

    frames = input("\nSpecify the number of frames needed to roll/flip in the desired axis (multiple data points separated by a comma): ").split(',')
    frames = list(map(float, frames))
    avg_frames = mean(frames)

    maneuver_time = calc_time(avg_frames, fps)
    maneuver_dps = calc_dps_round_to_10th(maneuver_time)
    print("\nIt takes {}s to roll/flip in this axis, corresponding to a rate of about {}°/s.".format(round(maneuver_time, 2), maneuver_dps))
    

requirements.txt

numpy==1.18.1
opencv-python-headless==4.2.0.32
pymediainfo==4.1

usage_example.txt

Specify DVR file path: /tmp/PICT0038.AVI
DVR's FPS: 25.057

Specify the number of frames needed to roll/flip in the desired axis (multiple data points separated by a comma): 18,19,18,17,24

It takes 0.77s to roll/flip in this axis, corresponding to a rate of about 470°/s.