Alternative to cv2.VideoCapture's set method for reliable frame seeking

seekToOpenCVReader.py

def seekTo(cap, position):
	''' 
  	Work around bug in OpenCV set method: https://github.com/opencv/opencv/issues/9053
  
	The alternative routine to seek in the video file, a bit slow.
	Required because FFMPEG can seek only to closest I-frames and we
	have to manually read all the P-frames until we reach the position
	'''
	positiontoset = position
	pos = -1
	cap.set(cv2.CAP_PROP_POS_FRAMES, position)
	while pos < position:
		ret, image = cap.read()
		pos = cap.get(cv2.CAP_PROP_POS_FRAMES)
		if pos == position:
			return image
		elif pos > position:
			positiontoset -= 1
			cap.set(cv2.CAP_PROP_POS_FRAMES, positiontoset)
			pos = -1