Video writing in Computer Vision - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to open a video writer with the correct fourcc codec.

Computer Vision

import cv2
fourcc = cv2.VideoWriter_fourcc(*'[1]')
out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640,480))

Drag options to blanks, or click blank then click option'

AH264

BMP4V

CMJPG

DXVID

Attempts:

3 left

💡 Hint

Common Mistakes

Using an unsupported codec string causes the video writer to fail.

Forgetting to unpack the string with * in VideoWriter_fourcc.

The 'XVID' codec is commonly used for AVI video writing in OpenCV.

2fill in blank

medium

Complete the code to write a frame to the video file.

Computer Vision

ret, frame = cap.read()
if ret:
    [1].write(frame)

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Acap

Bout

Cframe

Dcv2

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to write frames using the capture object 'cap'.

Calling write on the frame itself instead of the writer.

The VideoWriter object 'out' is used to write frames to the video file.

3fill in blank

hard

Fix the error in the code to release the video writer properly.

Computer Vision

out = cv2.VideoWriter('output.avi', fourcc, 20.0, (640,480))
# ... writing frames ...
[1].release()

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Acv2

Bframe

Cout

Dcap

Attempts:

3 left

💡 Hint

Common Mistakes

Calling release on the capture object instead of the writer.

Forgetting to release the writer causing file corruption.

The release() method must be called on the VideoWriter object 'out' to properly close the file.

4fill in blank

hard

Fill both blanks to create a VideoWriter with MJPG codec and 30 FPS.

Computer Vision

fourcc = cv2.VideoWriter_fourcc(*'[1]')
out = cv2.VideoWriter('output.avi', fourcc, [2], (640,480))

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AMJPG

BXVID

C30.0

D20.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong codec string causing unsupported format.

Setting FPS to a wrong value causing playback issues.

MJPG is a common codec and 30.0 sets the frames per second to 30.

5fill in blank

hard

Fill all three blanks to write frames only if the frame is read successfully and convert it to grayscale before writing.

Computer Vision

ret, frame = cap.read()
if [1]:
    gray = cv2.cvtColor(frame, [2])
    [3].write(gray)

Drag options to blanks, or click blank then click option'

Aret

Bcv2.COLOR_BGR2GRAY

Cout

Dframe

Attempts:

3 left

💡 Hint

Common Mistakes

Writing frames without checking if read was successful.

Using wrong color conversion code causing errors.

Writing to the wrong object instead of the VideoWriter.

Check if ret is True, convert frame to grayscale using cv2.COLOR_BGR2GRAY, then write using 'out'.