Python CV2 slow response time on keys

Question

I have been coding a video player to test if I can play and pause a video in Python. My problem is that whenever I press a key, its irresponsive and needs continuous presses to work, and the effect is random.

If anyone knows what could be causing this, it would be of great help.

import cv2

cap = cv2.VideoCapture('testvideo.mp4')

length = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))

isPlaying = False


def onchange(trackbar_value):
    cap.set(cv2.CAP_PROP_POS_FRAMES, trackbar_value)
    err, vid = cap.read()
    cv2.imshow('player', vid)
    pass


start = 0

cv2.namedWindow('player')
cv2.createTrackbar('test', 'player', start, length, onchange)

onchange(1)

while cap.isOpened():
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
    elif cv2.waitKey(1) & 0xFF == ord('p'):
        isPlaying = not isPlaying

    ret, player = cap.read()

    if cv2.waitKey(20) == 27:
        break
    if isPlaying:
        cv2.imshow('test', 'frame')

    elif cap.get(cv2.CAP_PROP_POS_FRAMES) >= length:
        break

cap.release()
cv2.destroyAllWindows()

Answer 1

I fixed it by changing this part in the while cap.isOpened() loop:

keyPress = cv2.waitKey(20)
ret, player = cap.read()
if keyPress & 0xFF == ord('q'):
    break
elif keyPress & 0xFF == ord('p'):
    isPlaying = not isPlaying

once I removed the

if cv2.waitKey(20) == 27:
    break

line, it worked much better than before too.

All of this sped up the project, and everything works fine now