How to capture a raw frame using OpenCV (python, should be "almost" the same with C++ besides creating a Mat first) compiled with V4L2 support

opencv_raw_capture_v4l2.py

# $ v4l2-ctl --list-formats-ext
# It shows my webcam supports MJPG and YUYV
# More details https://www.kernel.org/doc/html/v4.8/media/uapi/v4l/pixfmt-013.html

# And here we have some explanations about the flags available
# https://docs.opencv.org/4.x/d4/d15/group__videoio__flags__base.html

import cv2

cap = cv2.VideoCapture(0, cv2.CAP_V4L2) # I don't really need the CAP_V4L2 since it's the default
print(cap.getBackendName()) # just confirming

print(cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M', 'J', 'P', 'G')))
# if the command returns False, it means it was not accepted
# I could also use cv2.VideoWriter_fourcc('Y', 'U', 'Y', 'V')

print(cap.set(cv2.CAP_PROP_CONVERT_RGB, 0)) 
# if the command returns False, it means it was not accepted

print(cap.get(cv2.CAP_PROP_BUFFERSIZE))
# You may want to change the buffer size too:
# cap.set(cv2.CAP_PROP_BUFFERSIZE, 1)

# Curiously, the format changes only after the first frame was retrieved
print(cap.get(cv2.CAP_PROP_FORMAT))

ret, frame = cap.read()
# and the frame should be raw!

# Curiously, the format changes only after the first frame was retrieved
print(cap.get(cv2.CAP_PROP_FORMAT))

# print all formats, with codes:
# for i in dir(cv2):
#   if "CV_" in i:
#     print(i, getattr(cv2,i))