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Python: How to get image from USB Webcam?

I am very new in programming with python :)
My Setup:
Windows 11 Pro
Python 3.7
OpenCV 4.7
Webcam: HD Pro Webcam C920 from logitech
I want to access the camera image in Python. Everything works with my integrated camera.
When I want to access the USB camera, nothing works. I do not get video from my USB webcam.
I try the following code to see, if there is a camera.
import cv2
cap = cv2.VideoCapture(0)
print(cap.isOpened())
It works with my integrated Webcam. I get a True
With cap = cv2.VideoCapture(2) i get False
But if i try this with cap = cv2.VideoCapture(1) i get nothing back and there is no error. The program just keeps running. My conclusion: Somehow the USB camera has to work. Otherwise I would also expect a False for cap = VideoCapture(1).
I have already found and tried many things on the Internet. Unfortunately, nothing has helped.
I have also tried pygame, but that does not seem to run under windows.
How do I get video from my USB camera?
Thanks for your help :)

opencv python camera permission issue on Windows 10

While running a simple opencv video capture script, i am getting False as the result. I suspect it is due to some security setting in Windows 10 which is not allowing camera access. I checked Privacy > Camera settings, but there was no option to allow a script to access the camera. I can see that the camera is not turned on when running the following opencv based test script.
import cv2
cap = cv2.VideoCapture(0)
while(True):
ret, frame = cap.read()
print(ret)

The Key to the answer is "Give time for Microsoft Windows to initalize WebCAM"
import time
capWebcam = cv2.VideoCapture(0)
time.sleep(1.000) # Make sure, you need to give time
# for MS Windows to initialize Camera

It's called "Allow access to classic application" or "Desktop applications" something like this in the bottom of the setting page, under Windows Store type applications.
This gain camera access to all EXE and DLL standalone applications.
One setting for all of them.
More info on exceptions here https://support.microsoft.com/en-us/help/4468234/windows-10-desktop-apps-and-privacy
Works for me in
'cv2.__version__ 4.2.0'

just installed latest opencv and python8 on latest windows10.
As suggested in previous helpful answers, after checking windows camera security setting, adding time delay, and running windows camera app, the program works fine.

Open CV cannot read frames from USB camera on Raspberry Pi

I have a Logitech c270 usb webcam connected to my Raspberry Pi 3, running on a Jessie image. I have tried to capture frames with this simple tutorial code on
http://www.pyimagesearch.com/2016/02/22/writing-to-video-with-opencv/
Whenever I try to read frames in the while loop, it gives out this error:
NoneType object has no attribute 'shape'
I have printed out the vs.read() function and it also returns None object.
What can I do to resolve this problem?
NOTE: When I executed cmake to build the binaries for Open CV 3.1 on Raspberry Pi, I havent specified OpenCV to use V4L. Could this be a problem?
Thanks in advance.

It's Because your video stream object does not get attached with the camera. Hence no image is displayed.
If you are using Pi Camera, then make sure to type --picamera 1 as an argument while running the script.
else your camera is not connected to your Pi correctly.

grab frame NTSCtoUSB dongle, opencv2, python wrapper

Context:
I have been playing around with python's wrapper for opencv2.
I wanted to play with a few ideas and use a wide angle camera similar to 'rear view' cameras in cars.
I got one from a scrapped crash car (its got 4 wires) I took an educated guess from the wires color codding, connect it up so that I power the power and ground line from a usb type A and feed the NTSC composite+ composite- from an RCA connector.
I bought a NTSC to usb converter like this one.
It came with drivers and some off the shelf VHStoDVD software.
the problem:
I used the run of the mill examples online to trial test it like this:
import numpy as np
import cv2
cam_index=0
cap=cv2.VideoCapture(cam_index)
print cap.isOpened()
ret, frame=cap.read()
#print frame.shape[0]
#print frame.shape[1]
while (cap.isOpened()):
ret, frame=cap.read()
#gray=cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
cv2.imshow('frame', frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
#release and close
cap.release()
cv2.destroyAllWindows()
this is the output from shell:
True
Traceback (most recent call last):
File "C:/../cam_capture_.py", line 19, in <module>
cv2.imshow('frame', frame)
error: ..\..\..\..\opencv\modules\highgui\src\window.cpp:261: error: (-215) size.width>0 && size.height>0 in function cv::imshow
>>>
key Observations:
SCREENSHOTS
in control panel the usb dongle is shown as 'OEM capture' in Sound Video & Game controllers . So it's not seen as a simple plug and play Webcam in 'Imaging devices'
If I open the VHStoDVD software I need to configure 2 aspects:
set as Composite
set enconding as NTSC
then the camera feed from the analog camera is shown OK within the VHStoDVD application
When I open the device video channel in FLV (device capture). The device stream is just a black screen but IF i open the VHStoDVD software WHILE flv is streaming I get the camera's feed to stream on FLV and a black screen is shown on the VHStoDVD feed. Another important difference is that there is huge latency of aprox 0.5sec when the feed is in FLV as opposed to running in VHStoDVD.
When running "cam_capture.py" as per the sample code above at some put during runtime i will eventually get a stop error code 0x0000008e:
detail:
stop: 0x0000008E (0xC0000005, 0xB8B5F417, 0X9DC979F4, 0X00000000 )
ks.sys - Address B8B5F417 base at B8B5900, Datestamp...
beg mem dump
phy mem dump complete
5.if i try to print frame.shape[0] or frame.shape[1] I get a type error say I cannot print type None
6.if try other cam_index the result is always false
TLDR:
In 'control panel' the camera device is under 'sound video & game controllers' not under 'imaging devices';
The cam_index==zero;
The capture.isOpened()=True;
The frame size is None;
If VHStoDVD is running with composite NTSC configured the camera works , obviously you cant see the image with printscreen in attachment but trust me ! ;)
Is there any form of initialisation of the start of communication with the dongle that could fix this i.e. emulate VHStoDVD settings (composite+NTSC)? I thought I could buspirate the start of comms between VHStoDVD and the dongle but it feels like I am going above and beyond to do something I thought was a key turn solution.
Any constructive insights, suggestion , corrections are most welcome!
Thanks
Cheers

Ok , so after deeper investigation the initial suspicion was confirmed i.e. because the NTSC dongle is not handled as an imaging device (it's seen as a Video Controller , so similar to an emulation of a TV Tuner card ) it means that although we are able to call cv2.VideoCapture with cam_index=0 the video channel itself is not transmitting because we are required to define a bunch of parameters
encoding
frame size
fps rate etc
The problem is because the device is not supported as an imaging device calling cv2.VideoCapture.set(parameter, value) doesn't seem to change anything on the original video feed.
I didn't find a solution but I found a work around. There seems to be quite a few options online. Search for keywords DV to webcam or camcorder as a webcam.
I used DVdriver (http://www.trackerpod.com/TCamWeb/download.htm) (i used the trial because I am cheap!).
Why does it work?
As much as I can tell DVdriver receives the data from the device which is set as a Video controller (similar to a capture from "Windows Movie Maker" or ffmpeg) and then through "fairydust" outputs the frames on cam_index=0 (assumed no other cam connected) as an 'imaging device' webcam.
Summary
TLDR use DVdriver or similar.
I found a workaround but I would really like to understand it from first principles and possible generate a similar initialisation of the NTSC dongle from within python, without any other software dependencies but until then, hopefully this will help others who were also struggling or assuming it was a hardware issue.
I will now leave you with some Beckett:
Ever tried. Ever failed. No matter. Try again. Fail again. Fail better. (!)

It's a few months late, but might be useful. I was working on a Windows computer and had installed the drivers that came with the device, I tried the same code as your question with an Ezcap from Somagic and got the same error. Since "frame is None," I decided to try an if statement around it - in case it was an initialization error. Placing into the loop:
if frame is None:
print 0
else:
print 1
The result is: 01110111111111111111111111111...
And if the frame = cap.read(), above the loop is commented out - I get: 00111111111111111...
So for my device capture device it appears to be working for all frames beyond the 5th are captured. I'm not sure why this is, but it might be a useful work around for now.
Disclaimer: Unfortunately, my camera input is currently in a radiation field so I can't get to it for a couple of weeks to make sure it works for sure. However, the images are currently a black frame (which is expected without proper input).

I faced the same issue. As a workaround, I first tried the solution proposed by #user3380927 and it worked indeed. But since I didn't want to rely on an external software, I started tweaking parameters using opencv in Python.
This lines of code worked like a charm (you have to insert them before reading the frame for the first time):
cam.set(cv2.CAP_FFMPEG,True)
cam.set(cv2.CAP_PROP_FPS,30)
So, the full code for basic camera reading is as follows:
import cv2
cam = cv2.VideoCapture(1)
cam.set(cv2.CAP_FFMPEG,True)
cam.set(cv2.CAP_PROP_FPS,30)
while(True):
ret,frame = cam.read()
cv2.imshow('frame',frame)
if (cv2.waitKey(1) & 0xFF == ord('q')):
break
cam.release()
cv2.destroyAllWindows()
You can then apply image processing operations as usual. Just for reference, this was my configuration:
Opencv 3.1.0
Python 2.7.5
Windows 8.1
Elgato Video Capture device (this was also shown as Sound Video & Game controllers)

How to stop SimpleCV camera stream?

I'm trying to learn SimpleCV using Python 2.7 in IDLE.
Once the camera form SimpleCV is initialized the camera become unavailable to other programs like native webcam application or skype etc.
from SimpleCV import *
camera = Camera()
After restarting the pc or logoff and logon the webcam becomes to those applications. It seems that even closing out from python IDLE, it doesn't close the camera stream. Is there any way to stop the camera stream of simplecv?

I couldn't replicate your issue, but if the webcam is still running even after your program terminates/you close IDLE, you can end the camera by going into task manager and killing all running Python processes.
After some experimenting, I found that if you want to accomplish the same thing directly inside the code, you could try simply deleting the reference altogether:
>>> import SimpleCV as scv
>>> cam = scv.Camera()
>>> del cam
Calling del cam caused the webcam indicator light on my laptop to turn off. Granted, this appears to be an undocumented (??) solution, so I'm not sure how robust it is. I would probably try testing this on several different laptops/webcams first, to make sure it works reliably and consistently.