Topic: Python OpenCV – Part 4: Video Processing, Webcam Capture, and Real-Time Operations

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1. Reading Video from File

import cv2

cap = cv2.VideoCapture('video.mp4')

while cap.isOpened():
    ret, frame = cap.read()
    if not ret:
        break

    cv2.imshow('Video Frame', frame)

    if cv2.waitKey(25) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

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2. Capturing Video from Webcam

cap = cv2.VideoCapture(0)  # 0 is usually the built-in webcam

while True:
    ret, frame = cap.read()
    if not ret:
        break

    cv2.imshow('Webcam Feed', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

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3. Saving Video to File

fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640, 480))

cap = cv2.VideoCapture(0)

while True:
    ret, frame = cap.read()
    if not ret:
        break

    out.write(frame)  # write frame to output file
    cv2.imshow('Recording', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
out.release()
cv2.destroyAllWindows()

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4. Real-Time Video Processing

• Example: Convert webcam feed to grayscale live.

cap = cv2.VideoCapture(0)

while True:
    ret, frame = cap.read()
    if not ret:
        break

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    cv2.imshow('Grayscale Webcam', gray)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

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Summary

• You can capture video from files or webcams easily with OpenCV.

• Real-time processing lets you modify frames on the fly (filters, detections).

• Saving video requires specifying codec, frame rate, and resolution.

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Exercise

• Write a program that captures webcam video, applies Canny edge detection to each frame in real-time, and saves the processed video to disk. Quit when pressing 'q'.

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#Python #OpenCV #VideoProcessing #Webcam #RealTime

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