try setting CAP_PROP_CONVERT_RGB to false/0 on the VideoCapture object. that’s a feature for camera capture but maybe it’ll work on video files too.
yeah that’ll work, I just tested it. it might warn, but that’s fine. the frame will have 4 channels.
if you have trouble, set it in the constructor. that’s like
vid = cv.VideoCapture(
filepath, cv.CAP_FFMPEG, # CAP_ANY might work too
[cv.CAP_PROP_CONVERT_RGB, 0])