Video Capture Using OpenCV

Introduction

OpenCV (Open Source Computer Vision Library) is a widely used open-source computer vision and machine learning library. One of its many capabilities is capturing and processing video streams from cameras or video files. This feature is essential for applications like video surveillance, motion detection, and real-time video processing.

Syntax for Video Capture

To capture video using OpenCV, the cv2.VideoCapture() class is used. The syntax is as follows:

• source: The video source. It can be the device index for a camera (e.g., 0 for the default camera) or the path to a video file.

Example

Here is a simple example to demonstrate how to capture video from a webcam using OpenCV:

import cv2


# Initialize the video capture object (0 for the default camera)
cap = cv2.VideoCapture(0)


# Check if the camera opened successfully
if not cap.isOpened():
    print("Error: Could not open video source.")
else:
    # Capture video frame-by-frame
    while True:
        ret, frame = cap.read()  # Read a frame from the video source
        
        if not ret:
            print("Error: Failed to capture video frame.")
            break
        
        # Display the resulting frame
        cv2.imshow('Video Capture', frame)
        
        # Break the loop if the 'q' key is pressed
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break


# Release the video capture object and close all OpenCV windows
cap.release()
cv2.destroyAllWindows()

In this example:

• We initialize the video capture object to capture from the default camera using cv2.VideoCapture(0).
• We check if the camera opened successfully with cap.isOpened().
• We enter a loop to read frames from the video source using cap.read().
• We display each frame using cv2.imshow().
• The loop breaks if the ‘q’ key is pressed.
• Finally, we release the video capture object and close all OpenCV windows using cap.release() and cv2.destroyAllWindows().

This simple script effectively demonstrates how to capture and display video frames using OpenCV.