Video capture using OpenCV if you wanna try it. Works on my mac

test.py

import numpy as np
import cv2
from PIL import ImageGrab

fourcc = cv2.cv.CV_FOURCC(*'XVID') # or cv2.VideoWriter_fourcc('X','V','I','D') if you use opencv 3.0
vid = cv2.VideoWriter('record.avi', fourcc, 8, (500,490))
while(True):
    img = ImageGrab.grab(bbox=(100, 10, 600, 500)) #x, y, w, h
    img_np = np.array(img)
    #frame = cv2.cvtColor(img_np, cv2.COLOR_BGR2GRAY)
    vid.write(img_np)
    cv2.imshow("frame", img_np)
    key = cv2.waitKey(1)
    if key == 27:
        break    

vid.release()
cv2.destroyAllWindows()