Generic UVC camera preview and FPS measure

uvc_test.py

#!/usr/bin/env python3

# Key controls:
# q - quit
# c - capture

import cv2
import numpy as np
import time

# Configurable flags. Note: to get an accurate FPS measurement, disable 'show_frame'
calc_fps = True
show_frame = True

# TODO: change device number here
cam = cv2.VideoCapture(0)

time_start = time.monotonic()
fps_interval = 1
counter = 0

while True:
    ret, frame = cam.read()

    if calc_fps:
        time_now = time.monotonic()
        time_diff = time_now - time_start
        counter += 1
        if time_diff > fps_interval:
            print("FPS: ", counter / time_diff)
            counter = 0
            time_start = time_now

    if show_frame:
        cv2.imshow("camera", frame)

    key = cv2.waitKey(1)
    if key == ord('q'):
        break
    elif key == ord('c'):
        name = 'cap-' +  time.strftime("%H:%M:%S", time.localtime()) + '.png'
        cv2.imwrite(name, frame)
        print("Saved to:", name)