基于python和opencv的视频捕获帧率限制

Question

我正试图从ip摄像机捕捉视频，并保存为avi视频文件。同时脚本将包含人脸的帧保存为jpeg文件。当脚本执行这些任务时，cpu使用率约为100%。正因为如此，我只想限制人脸检测的帧率。

face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
now = datetime.datetime.now()
strtime = str(now)
cap = cv2.VideoCapture('rtsp://root:root@10.10.10.56:554/stream/profile1=r')




fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('1/video/%s.avi' % strtime,fourcc, 10.0 , (960,540))

if cap.isOpened():


    while(True):
        if cap.set(cv2.CAP_PROP_FPS,4):

            try:


                ret, frame = cap.read()

                if ret==True:


                    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
                    out.write(frame)

                    if cv2.waitKey(1) & 0xFF == ord('q'):
                        break
                    faces = face_cascade.detectMultiScale(gray,
                                                          scaleFactor=1.5,
                                                          minNeighbors=6,
                                                          minSize=(30,30))
                    for (x,y,w,h) in faces:
                        cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),
                        cv2.imwrite('1/frames/%sf%s.jpg'%(now,str(cap.get(cv2.CAP_PROP_POS_FRAMES))), frame)


                    cv2.imshow('frame', frame)


            except KeyboardInterrupt:
                cap.release()
                out.release()
                cv2.destroyAllWindows()
                sys.exit(0)
                pass

else:
    print "Unable to connect"


cap.release()
out.release()
cv2.destroyAllWindows()
sys.exit(0)

Answer 1

经过多次尝试，我找到了一个适合我需要的解决方案。我计算了帧数，并使人脸检测的for循环每10帧工作一次。当我设置我的相机流10 fps视频，这应该意味着人脸检测流是1 fps。

编码的解决方案：

if int(cap.get(cv2.CAP_PROP_POS_FRAMES)) % 10 == 0: 
    faces = face_cascade.detectMultiScale(gray,
                                          scaleFactor=1.5,
                                          minNeighbors=5,
                                          minSize=(30, 30))
    for (x, y, w, h) in faces:
         cv2.rectangle(frame, (x, y), (x + w, y + h), (255, 0, 0))
         cv2.imwrite('1/frames/%sf%s.jpg'%(now, str(cap.get(cv2.CAP_PROP_POS_FRAMES))), frame)