VideoCapture

Context manager

with VideoCapture(0) as v:
    # etc. etc.

Automatically release the resources managed by the VideoCapture, even if an error occurs.

Code at video.py:35-40 (VideoCapture.__enter__ and VideoCapture.__exit__).

Random access

>>> with VideoCapture("video.avi") as v:
...     print(f"Video containts {len(v)} frames")
...     cv2.imwrite("frame_7.png", v[6])
Video contains 203 frames
>>> with VideoCapture(0) as v:
...     len(v)
TypeError: VideoCapture source does not support random access

For video sources that support it, allow random access to frames. If the source is a webcam or similar, calling len or indexing the video will throw a TypeError.

Code at video.py:43-61 (VideoCapture.__len__ and VideoCapture.__getitem__)

Iterable

with VideoCapture(0) as v:
    for frame in v:
        cv2.imshow("Frame", frame)
        if cv2.waitKey(1) & 0xFF == ord("q"):
            break

Iterating over a VideoCapture gives the frames of the underlying video stream. If a read fails or the video is no longer open, the iterator ends.

Code at video.py:64-78 (VideoCapture.__iter__ and VideoCapture.__next__).

Property access

>>> with VideoCapture(0) as v:
... 	print(v.frame_width)
... 	print(v.shape)
... 	print(v.fps)
640
(640, 480)
30.0

The various properties accessed with get(cv2.CAP_PROP_PROPERTY_NAME) are mapped to VideoCapture.property_name. For convenience, width and height are provided as synonyms for frame_width and frame_height, respectively; and shape returns a (height, width) tuple.

Code at video.py:81-98 (VideoCapture.__getattr__ and VideoCapture.__setattr__, with the properties following those two methods handling special cases).

Transparent wrapper

VideoCapture subclasses cv2.VideoCapture and doesn't override any methods, so it can act as a drop-in replacement for cv2.VideoCapture without causing errors or affecting existing behaviour (ideally; this has not been extensively tested).

VideoWriter

Context manager

with VideoWriter("file.mp4", cv2.VideoWriter_fourcc(*"mp4v"), 30, (640, 480)) as vw:
    # etc. etc.

Automatically release the resources held by the VideoWriter even if an error occurs.

Code at video.py:146-151 (VideoWriter.__enter__ and VideoWriter.__exit__).

Transparent wrapper

VideoWriter subclasses cv2.VideoWriter and doesn't override any methods, so it can act as a drop-in replacement for cv2.VideoWriter without causing errors or affecting existing behaviour (ideally; this has not been extensively tested).