python - OpenCV VideoCapture device index / device number

Question

I have a python environment (on Windows 10) that uses OpenCV VideoCapture class to connect to multiple usb cameras.

As far as I know, there is no way to identify a specific camera in OpenCV other than the device parameter in the VideoCapture class constructor / open method.

The problem is that the device parameter changes depending on how many cameras are actually connected and to which usb ports.

I want to be able to identify a specific camera and find its "device index" or "camera index" no matter how many cameras are connected and to which usb ports.

Can somebody please suggest a way to achieve that functionality? python code is preferable but C++ will also do.

Answer 1

Preface, I do not use windows, and this hasn't been tested, but is a combination of answers and source found from online, with some modifications.

Walk the USB registry keys and parse the sub_key strings:

import _winreg
usb_devices=[]
index = 0
with _winreg.OpenKey(_winreg.HKEY_LOCAL_MACHINE, 'SYSTEMCurrentControlSetEnumUSB') as root_usb:
    while True:
        try:
            subkey = _winreg.EnumKey(root_usb, index)
            usb_devices.append(subkey)
            index += 1
        except WindowError as e:
            if e[0] == 259: # No more data is available
                break
            elif e[0] == 234: # more data is available
                index += 1
                continue
            raise e
print('parse these', usb_devices)

Or possibly Popen a wmic subprocess and parse the stdout:

from subprocess import Popen, PIPE
results1 = Popen(['wmic', 'path', 'win32_pnpentity', 'get', 'caption' '/format:list'], stdout=PIPE)
results2 = Popen(['wmic','path','Win32_SerialPort','get','DeviceID^,Caption^,Description^,Name^,ProviderType','/format:list'], stdout=PIPE)
print('parse these', results1.stdout.read())
print('parse these', results2.stdout.read())

Related, linux, mac, and windows c++:

• https://superuser.com/questions/902012/how-to-identify-usb-webcam-by-serial-number-from-the-linux-command-line
• https://superuser.com/questions/883053/mac-os-x-equivalent-of-udevadm-info-a-n-dev-ttyacm0
• get serial com port description in windows batch
• Detecting USB Insertion / Removal Events in Windows using C++
• windows - How to enumerate all connected USB devices' device path?
• https://msdn.microsoft.com/en-us/library/aa394413(v=vs.85).aspx
• http://www.velleman.eu/images/tmp/usbfind.c
• http://www.bitpim.org/pyxr/c/projects/bitpim/src/comscan.py.html