Python cv2 讀取rtsp視頻流/USB攝像頭並顯示

安裝python 庫：
sudo apt install python-opencv

#!/bin/python
#### in rtsp server:
####  ffserver -f /etc/ffserver.conf &
#### ffmpeg -f v4l2 -i /dev/video0  -s 640x480 -r 24 -vcodec libx264 -an http://127.0.0.1:8090/feed1.ffm
import cv2

if __name__ == "__main__":
  cap = cv2.VideoCapture("rtsp://192.168.xx.xxx:8554/live1.h264")
  if cap.isOpened() :
    ret,frame=cap.read()
#    print "==== ret ===="
#    print ret
#    print "====print dir(frame)===="
#    print dir(frame)
#    print "====print frame.shape===="
#    print frame.shape
#    print "====print (frame.shape[0], frame.shape[1], frame.shape[2])===="
#    print (frame.shape[0], frame.shape[1], frame.shape[2])
#    print "====print frame.size===="
#    print frame.size
#    print "====print frame.data===="
#    #print frame.data
#    #print type(frame.data)
#    print "====print frame.copy===="
#    print frame.copy
#    print type(frame.copy)
#    print "====print frame.ctypes===="      
    #-------------------------------------------------------------------------------------------
    # ！！ frame.ctypes.data_as（c_char_p/c_void_p/...） 可以將python opencv讀取到的圖像轉爲
    #  C語言某種格式，在python傳遞參數給C語言的庫時很有用。
    #  frame.ctypes.data_as（c_char_p）：將一幀圖像的內存地址轉換爲C語言char*型
    #-------------------------------------------------------------------------------------------
    print frame.ctypes
    print type(frame.ctypes)       
    print "====print frame.imag===="
    #print frame.imag
    #print type(frame.imag)
    print "====print frame.tobytes===="
    print frame.tobytes
    print type(frame.tobytes)
  
  ##cap.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH,640)
  ##cap.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT,480)
  while cap.isOpened():
    ret,frame=cap.read()
    print (frame.shape[0], frame.shape[1], frame.shape[2])
#    print ret
#    print dir(frame)
#    print frame.shape
#    print frame.size
#    print frame.data
    cv2.imshow("frame",frame)
    cv2.waitKey(10)

以上代碼中註釋部分大多爲讀取視頻信息包括幀率，每幀圖像大小，內容等信息的測試，下面爲簡單案例，
分別爲讀取USB攝像頭數據和rtsp流數據，並顯示：

import cv2 
if __name__ == "__main__":
  ## 讀取rtsp視頻流並顯示
  cap = cv2.VideoCapture("rtsp://192.168.xx.xxx:8554/live1.h264")
  ## 讀取usb-came 0（/dev/video0） 
  #cap = cv2.VideoCapture(0)
  while cap.isOpened():
    (ret,frame)=cap.read()
    print (frame.shape[0], frame.shape[1], frame.shape[2])
    cv2.imshow("frame",frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
      break
  cv2.destroyWindow("frame")
  cap.release()