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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.

jmunsch
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Elad Maimoni
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3 Answers3

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As far as I know, openCV enumerates devices and uses the index of it as a camera index. But the way it enumerates can differ among backends. Anyway, if you can enumerate devices as OpenCV do, you can match the index of the device and its information depend on your code.

So, In Windows environment, you can use MSMF or DSHOW as a backend. If you are using MSMF as a backend, I made a simple function to list devices and match its name to its index. Here: https://github.com/pvys/CV-camera-finder.

If you are using DSHOW as a background, here's a nice article: https://www.codeproject.com/Articles/1274094/Capturing-Images-from-Camera-using-Python-and-Dire

Park
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  • CV-camera-finder (function get_MF_devices()) works great! My other approaches sometimes had the friendly name out of order with the OpenCV device numbers – slalomchip Nov 03 '20 at 13:11
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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, 'SYSTEM\CurrentControlSet\Enum\USB') 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++:

Community
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jmunsch
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    For some reason `winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, 'SYSTEM\CurrentControlSet\Enum\USB')` gives me a `SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 29-30: truncated \UXXXXXXXX escape` on Python 3.7/Windows 10. If I descend the key hierarchy one level at a time I can eventually enumerate the `USB` values but these are in the form `'VID_056A&PID_033C&MI_01'` etc, so I don't know how to relate these to the OpenCV camera index. – nekomatic Feb 25 '20 at 12:16
-1

If you can differentiate the cameras by their serial number or device and vendor id, you can loop through all video devices before opening with opencv and search for the camera device you want to open.

alex
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