change webcam settings in realtime

webcam_nerverot.py

#!/usr/bin/env python3

# Do violence to the Logitech C920s webcam settings in realtime
# To annoy your Zoom-mates by constantly changing the image

from pynput.keyboard import Listener
import os, sys
import random
import time


# Find out the name of the webcam device
lines = os.popen('v4l2-ctl --list-devices').read().lower().split('\n')
for i, line in enumerate(lines):
    if 'webcam' in line:
        device = lines[i+1].strip()
        break
print(f"device = [{device}]")
#device = '/dev/video3'  # on my system.


# parse the set of available (integer) controls
prefix_cmd = 'v4l2-ctl -d ' + device + ' '
ctrls_str = os.popen(prefix_cmd + '--list-ctrls | grep -v inactive | grep  "\(int\)"').read()
ctrls = []
for line in ctrls_str.split('\n'):
    words = line.strip().split()
    if ([] == words): break
    name, minval, maxval, stepval, value = words[0], int(words[4][4:]), \
        int(words[5][4:]), int(words[6][5:]), (words[8][6:])
    ctrls.append([name, minval, maxval, stepval, value])

print("ctrls = ",ctrls)

# Now go nuts
keep_running, reset = True, False



def on_press(key):  # how to make it stop
    global keep_running, reset
    if key.char in ['q','r']:
        keep_running = False
        if 'r' == key.char: reset=True
        return False  # shutdown the listener


listener =  Listener(on_press=on_press)
listener.start()
while keep_running==True:
    s = prefix_cmd
    for c in ctrls:
        val = random.randrange(c[1], c[2], c[3])
        s += '--set-ctrl='+c[0]+'='+str(val)+' '
    print(s)
    os.system(s)
    time.sleep(.5) # wait 500 ms, because driver can't keep up


# graceful exit
if reset:  # reset is because sometimes the program hangs and you get stuck with weird webcam settings
    print("\nOkay, stopping. Restoring factory webcam settings:")
    s = f'v4l2-ctl -d {device} --set-ctrl=brightness=128 --set-ctrl=contrast=128 --set-ctrl=saturation=128 --set-ctrl=gain=255 --set-ctrl=sharpness=128 --set-ctrl=backlight_compensation=0 --set-ctrl=pan_absolute=0 --set-ctrl=tilt_absolute=0  --set-ctrl=zoom_absolute=120'
else:
    print("\nOkay, stopping. Restoring previous webcam settings:")
    s = prefix_cmd
    for c in ctrls:
        s += '--set-ctrl='+c[0]+'='+str(c[4])+' '

print(s)
os.system(s)