Description
cv2.VideoWriter is creating a file but not writing anything in the video
Environment
Ubuntu 25.04
Python 3.13.3
Open CV 4.13.0
How to recreate
Create main.py with the file content.
Create a video file named video.mp4
mkdir .venv
python -m venv .venv
. .venv/bin/activate
pip install opencv-contrib-python
python main.py
And I get the following output with a corrupted output.mp4 file:
OpenCV Version:
4.13.0
codec
1983148141
shape
(1576, 770)
fps
24.0
However, if I run
ffmpeg -i output.mp4 out.mp4
out.mp4 works
File
import cv2
import time
video = cv2.VideoCapture("video.mp4")
fps = video.get(cv2.CAP_PROP_FPS)
shape = (int(video.get(cv2.CAP_PROP_FRAME_WIDTH)), int(video.get(cv2.CAP_PROP_FRAME_HEIGHT)))
fourcc = cv2.VideoWriter_fourcc(*"mp4v")
writer = cv2.VideoWriter("output.mp4", fourcc, fps, shape)
print("OpenCV Version:")
print(cv2.__version__)
print("codec")
print(fourcc)
print("shape")
print(shape)
print("fps")
print(fps)
time.sleep(1.0)
while True:
ret, frame = video.read()
if not ret or frame is None:
break
if frame.ndim == 2:
frame = cv2.cvtColor(frame, cv2.COLOR_GRAY2BGR)
writer.write(frame)
video.release()
writer.release()
Description
cv2.VideoWriteris creating a file but not writing anything in the videoEnvironment
Ubuntu 25.04
Python 3.13.3
Open CV 4.13.0
How to recreate
Create
main.pywith the file content.Create a video file named
video.mp4mkdir .venvpython -m venv .venv. .venv/bin/activatepip install opencv-contrib-pythonpython main.pyAnd I get the following output with a corrupted
output.mp4file:However, if I run
ffmpeg -i output.mp4 out.mp4out.mp4worksFile