Camera starts too late in Python application: what is the reason?

Question

Can you please help me with this? I have created a Python application that records/processes video files with opencv. It worked fine with all my previous cameras.

Recently we purchased 3 models of Logitech Webcams: very good quality, FPS controllable, You can manually alter the brightness, colorfulness, distance, etc, Actually, the best cameras among all the tested ones. However, it takes too long (about 2-2.5 minutes for the Logitech cameras to start in my application).

All the other cameras, including my laptop camera, start immediately or after a few seconds. What can be the reason of such lateness? I used the code suggested in the following link for AV recording: How to capture a video (AND audio) in python, from a camera (or webcam)

Answer 1

I used that code and had the same issues. The delay to start recording was inconsistent and occasionally the threads would hang after recording and crash my program. I came up with a much simpler solution that worked well for me. I also ended up with much higher quality videos in the end. Re-encoding the openCV videos with ffmpeg would always produce some weird distortions with my video.

The solution presently only works for Windows because it uses pywinauto and the built-in Windows Camera app. The last bit of the script does some error-checking to confirm the video successfully recorded by checking the timestamp of the name of the video.

https://gist.github.com/mjdargen/956cc968864f38bfc4e20c9798c7d670

import pywinauto
import time
import subprocess
import os
import datetime

def win_record(duration):
    subprocess.run('start microsoft.windows.camera:', shell=True)  # open camera app

    # focus window by getting handle using title and class name
    # subprocess call opens camera and gets focus, but this provides alternate way
    # t, c = 'Camera', 'ApplicationFrameWindow'
    # handle = pywinauto.findwindows.find_windows(title=t, class_name=c)[0]
    # # get app and window
    # app = pywinauto.application.Application().connect(handle=handle)
    # window = app.window(handle=handle)
    # window.set_focus()  # set focus
    time.sleep(2)  # have to sleep

    # take control of camera window to take video
    desktop = pywinauto.Desktop(backend="uia")
    cam = desktop['Camera']
    # cam.print_control_identifiers()
    # make sure in video mode
    if cam.child_window(title="Switch to Video mode", auto_id="CaptureButton_1", control_type="Button").exists():
        cam.child_window(title="Switch to Video mode", auto_id="CaptureButton_1", control_type="Button").click()
    time.sleep(1)
    # start then stop video
    cam.child_window(title="Take Video", auto_id="CaptureButton_1", control_type="Button").click()
    time.sleep(duration+2)
    cam.child_window(title="Stop taking Video", auto_id="CaptureButton_1", control_type="Button").click()

    # retrieve vids from camera roll and sort
    dir = 'C:/Users/michael.dargenio/Pictures/Camera Roll'
    all_contents = list(os.listdir(dir))
    vids = [f for f in all_contents if "_Pro.mp4" in f]
    vids.sort()
    vid = vids[-1]
    # compute time difference
    vid_time = vid.replace('WIN_', '').replace('_Pro.mp4', '')
    vid_time = datetime.datetime.strptime(vid_time, '%Y%m%d_%H_%M_%S')
    now = datetime.datetime.now()
    diff = now - vid_time
    # time different greater than 2 minutes, assume something wrong & quit
    if diff.seconds > 120:
        quit()
    
    subprocess.run('Taskkill /IM WindowsCamera.exe /F', shell=True)  # close camera app
    print('Recorded successfully!')


win_record(2)