The camera index isn't match with the real devices

[Sleepy-11]

I tried to build and installed on my laptop. And it seems that the listed camera isn't match the real devices, or at least the index which opencv uses. Below is the output:

Before inserting the USB camera:
❯ python .\test.py
OpenCV version: 4.5.5
0: HP HD Camera [(640, 480), (320, 180), (320, 240), (424, 240), (640, 360), (640, 480), (320, 180), (320, 240), (424, 240), (640, 360), (848, 480), (960, 540), (1280, 720)]
Select a camera (0 to 0): 0
Default width: 640.0, height: 480.0
[ WARN:0@16.323] global D:\a\opencv-python\opencv-python\opencv\modules\videoio\src\cap_msmf.cpp (539) `anonymous-namespace'::SourceReaderCB::~SourceReaderCB terminating async callback

After inserting the USB camera:

❯ python .\test.py
OpenCV version: 4.5.5
0: USB Camera [(1280, 720), (800, 600), (640, 480), (352, 288), (320, 240), (176, 144), (160, 120), (1280, 720), (800, 600), (640, 480), (352, 288), (320, 240), (176, 144), (160, 120), (1280, 720), (800, 600), (640, 480), (352, 288), (320, 240), (176, 144), (160, 120), (1280, 720), (800, 600), (640, 480), (352, 288), (320, 240), (176, 144), (160, 120)]
1: HP HD Camera [(640, 480), (320, 180), (320, 240), (424, 240), (640, 360), (640, 480), (320, 180), (320, 240), (424, 240), (640, 360), (848, 480), (960, 540), (1280, 720)]
Select a camera (0 to 1): 0
Default width: 640.0, height: 480.0
[ WARN:0@25.521] global D:\a\opencv-python\opencv-python\opencv\modules\videoio\src\cap_msmf.cpp (539) `anonymous-namespace'::SourceReaderCB::~SourceReaderCB terminating async callback

the test.py is the sample code in the repo README file.
After inserting the USB Camera, it seems the second webcam took the "0" index, and the integrated one became "1". But actually, the programs calls the integrated cam(i.e. HP HD Camera) when I input "0", and calls USB Camera when i input "1".

python version is 3.10.4, windows-capture-device-list is 1.1.0 and OS is windows 10.

Is there any idea how I can fix it?

[yushulx]

@Sleepy-11 I've never tested the API on a laptop. Probably the built-in camera always takes the 0 position. If you have two USB cameras, you can check whether USB cameras are listed in order. If you only have one USB camera, you can just reverse their order. Note: the index is determined by the camera list returned by DirectShow API. It may not be 100% equal to the index used by OpenCV.

[Sleepy-11]

@yushulx Thanks for the reply.
From my laptop view, the built-in camera could be placed on index "1" after the USB camera is inserted. And the DirectShow and OpenCV use different webcam sequence. :(

[Avasam]

@Sleepy-11 Consider upvoting and commenting on issues like opencv/opencv#4269 for OpenCV to expose their device sequence.