OpenCv's cv.VideoWriter output is BGR, even though I convert each frame to RGB before writing them

My code records some video, but in the video blue and red seem to be switched.

import cv2 as cv import numpy as np import asyncio #video assemble async def makeVideo(frames, w, h): output = 'output_video.mp4' fourcc = cv.VideoWriter_fourcc(*'mp4v') videowr = cv.VideoWriter(output, fourcc, 30, (w, h)) for frame in frames: videowr.write(cv.cvtColor(frame, cv.COLOR_BGR2RGB)) videowr.release() return output #video analysis async def analyse_vid(): #frames list frames = [] protection_mode_active = True cap = cv.VideoCapture(0) backSub = cv.createBackgroundSubtractorMOG2() if not cap.isOpened(): print("Cannot open camera") return width = int(cap.get(cv.CAP_PROP_FRAME_WIDTH)) height = int(cap.get(cv.CAP_PROP_FRAME_HEIGHT)) print(f'Width: {width} Height: {height}') last_warning_time = asyncio.get_event_loop().time() # Track the last warning time while protection_mode_active: ret, frame = cap.read() if not ret: print("Can't receive frame (stream end?). Exiting ...") break fg_mask = backSub.apply(frame) contours, _ = cv.findContours(fg_mask, cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE) min_contour_area = 500 large_contours = [cnt for cnt in contours if cv.contourArea(cnt) > min_contour_area] for cnt in large_contours: x, y, w, h = cv.boundingRect(cnt) cv.rectangle(frame, (x, y), (x + w, y + h), (0, 0, 255), 1) current_time = asyncio.get_event_loop().time() # Get the current time frames.append(frame) # Check if enough time has passed for cooldown if current_time - last_warning_time >= 5: # 5 seconds cooldown last_warning_time = current_time # Update the last warning time global final_video final_video = await makeVideo(frames, width, height) frames = [] cv.imshow('Frame', frame) if cv.waitKey(1) == ord('q'): break cap.release() cv.destroyAllWindows() #Video display async def display_vid(vid_path): cap = cv.VideoCapture(vid_path) if not cap.isOpened(): print('ERROR: could not open video') return while True: ret, frame = cap.read() if not ret: print("Video end") break cv.imshow('Video', frame) if cv.waitKey(1) & 0xFF == ord('q'): break cap.release() cv.destroyAllWindows() asyncio.run(analyse_vid()) asyncio.run(display_vid(final_video))

To replicate the problem:

Run the code. Wait for your camera capture to open Wait for ~5 seconds (or for a little freeze on the camera capture) press q

The screenshots below show actual vs expected output:

Screenshot of camera capture (input)

Screenshot of processed video capture (output):

These should be the same, but the colors are kind of inverted.

Why does this happen and how can I fix this?