Camera stream access with OpenCV in Drone Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main OpenCV function used to access a camera stream?

The main function is cv2.VideoCapture(). It opens the camera stream for capturing video frames.

beginner

How do you specify the default camera device in OpenCV?

You pass 0 as the argument to cv2.VideoCapture(0) to open the default camera on your device.

beginner

What method do you use to read a frame from the camera stream in OpenCV?

Use the read() method on the VideoCapture object. It returns two values: a boolean indicating success and the frame image.

intermediate

Why is it important to release the camera after use in OpenCV?

Releasing the camera with cap.release() frees the hardware resource so other programs or processes can use it.

beginner

How can you display the camera stream frames in a window using OpenCV?

Use cv2.imshow(window_name, frame) inside a loop to show each frame. Use cv2.waitKey() to refresh and detect key presses.

Which argument opens the default camera in OpenCV?

A None

B 1

C -1

D 0

Passing 0 to cv2.VideoCapture opens the default camera device.

What does the read() method return?

A A boolean and the frame image

B Only the frame image

C Only a boolean

D A string with frame info

read() returns a tuple: success flag (boolean) and the captured frame.

Why use cap.release() after capturing video?

A To save the video file

B To pause the video stream

C To free the camera hardware resource

D To reset the camera settings

Releasing the camera frees it for other uses.

Which function shows the video frame in a window?

A cv2.imshow()

B cv2.show()

C cv2.display()

D cv2.frame()

cv2.imshow() displays an image or frame in a window.

What does cv2.waitKey(1) do in a video loop?

A Starts the video capture

B Waits 1 millisecond for a key press

C Closes the window immediately

D Waits 1 second for a key press

waitKey(1) waits 1 ms and processes GUI events, allowing frame refresh and key detection.

Explain the steps to access and display a live camera stream using OpenCV.

Think about opening, reading, showing, and closing the camera stream.

Why is it important to handle the camera resource properly in drone programming?

Consider what happens if the camera is not released.