The problem maybe is with the codec of the camera stream and not with the FPS itself, for example, if your camera only supports YUYV it is probably that you could only work with some specific FPS, try with the app guvcview to check this in a GUI.

Try to change the codec to MJPG and then change the FPS using CAP_PROP_FPS. I'm using a Logitech C922 pro and this works for me to configure 1080p and 30fps, if you have other camera probably yu need to use a lower resolution to achieve 30fps:

import cv2 as cv
def decode_fourcc(v):
    v = int(v)
    return "".join([chr((v >> 8 * i) & 0xFF) for i in range(4)])

def setfourccmjpg(cap):
    oldfourcc = decode_fourcc(cap.get(cv.CAP_PROP_FOURCC))
    codec = cv.VideoWriter_fourcc(*'MJPG')
    res=cap.set(cv.CAP_PROP_FOURCC,codec)
    if res:
        print("codec in ",decode_fourcc(cap.get(cv.CAP_PROP_FOURCC)))
    else:
        print("error, codec in ",decode_fourcc(cap.get(cv.CAP_PROP_FOURCC)))
cap = cv.VideoCapture(CAMERANUM)
cu.setfourccmjpg(cap)
w=1920
h=1080
fps=30
res1=cap.set(cv.CAP_PROP_FRAME_WIDTH,w)
res2=cap.set(cv.CAP_PROP_FRAME_HEIGHT,h)
res3=cap.set(cv.CAP_PROP_FPS,fps)

then resume your normal video capture polling loop.

In OpenCV 3.2, drop the CV in front of the flag. This should work just fine

videoCapture = cv2.VideoCapture(file_path)
fps = videoCapture.get(cv2.CAP_PROP_FPS)
size = (int(videoCapture.get(cv2.CAP_PROP_FRAME_WIDTH)),
        int(videoCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))

Performing pip install python-opencv fixed the problem and the FPS is correctly detected.

EDIT: tested with python 3.8 and indeed it is pip install opencv-python. Cannot remember two years ago what python I was using.

EDIT November 2022: please also check Perry's answer below, if you are using a newer opencv-python version

Setting a frame rate doesn't always work like you expect. It depends on two things:

1. What your camera is capable of outputting.
2. Whether the current capture backend you're using supports changing frame rates.

So point (1). Your camera will have a list of formats which it is capable of delivering to a capture device (e.g. your computer). This might be 1920x1080 @ 30 fps or 1920x1080 @ 60 fps and it also specifies a pixel format. The vast majority of consumer cameras do not let you change their frame rates with any more granularity than that. And most capture libraries will refuse to change to a capture format that the camera isn't advertising.

Even machine vision cameras, which allow you much more control, typically only offer a selection of frame rates (e.g. 1, 2, 5, 10, 15, 25, 30, etc). If you want a non-supported frame rate at a hardware level, usually the only way to do it is to use hardware triggering.

And point (2). When you use cv.VideoCapture you're really calling a platform-specific library like DirectShow or V4L2. We call this a backend. You can specify exactly which backend is in use by using something like:

cv2.VideoCapture(0 + cv2.CAP_DSHOW)

There are lots of CAP_X's defined, but only some will apply to your platform (e.g CAP_V4L2 is for Linux only). On Windows, forcing the system to use DirectShow is a pretty good bet. However as above, if your camera only reports it can output 30fps and 60fps, requesting 10fps will be meaningless. Worse, a lot of settings simply report True in OpenCV when they're not actually implemented. You've seen that most of the time reading parameters will give you sensible results though, however if the parameter isn't implemented (e.g exposure is a common one that isn't) then you might get nonsense.

You're better off waiting for a period of time and then reading the last image.

Be careful with this strategy. Don't do this:

while capturing:
    res, image = cap.read()
    time.sleep(1)

you need to make sure you're continually purging the camera's frame buffer otherwise you will start to see lag in your videos. Something like the following should work:

frame_rate = 10
prev = 0

while capturing:

    time_elapsed = time.time() - prev
    res, image = cap.read()

    if time_elapsed > 1./frame_rate:
        prev = time.time()

        # Do something with your image here.
        process_image()

For an application like a hand detector, what works well is to have a thread capturing images and the detector running in another thread (which also controls the GUI). Your detector pulls the last image captured, runs and display the results (you may need to lock access to the image buffer while you're reading/writing it). That way your bottleneck is the detector, not the performance of the camera.

For OpenCV 3.x:

cap = cv2.VideoCapture(1)
cap.set(cv2.CAP_PROP_FPS, 60)

For OpenCV 2.x:

cap = cv2.VideoCapture(1)
cap.set(cv2.cv.CV_CAP_PROP_FPS, 60)

This worked correctly with my "PS3 Eye" camera.

CV_CAP_PROP_FPS only works on videos as far as I know. If you want to capture video data from a webcam you have to time it correctly yourself. For example use a timer to capture a frame from the webcam every 40ms and then save as 25fps video.

A bit too late but searching on same topic (not specific to Vivotek Camera but more on mpeg problem with openCV) :

• Video is encoded
• OpenCV uses FFMPEG
• Encoding use key frames
• When skipping some frames encoding can't give you the exact frame you want

see similar question :

• Getting individual frames using CV_CAP_PROP_POS_FRAMES in cvSetCaptureProperty

• How can I get one single frame from a video file?

• Problem with CV_CAP_PROP_POS_FRAMES setting next frame number

  desired position        key frame (this is where the cursor will stop)
   |   |                       |                    |
   |   >                       |                    |
   |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
  

  Sample code using openCV 2.4.8 / VS2013 with trackbar :

• tested with AVI format [MPEG4 Video (H264)] : setting frame position works fine

• tested with MPG format [MPEG1/MPEG2] : setting frame position works fine

  double currentPos = capture.get(CV_CAP_PROP_POS_FRAMES);
  std::cout << "CV_CAP_PROP_POS_FRAMES = " << currentPos << std::endl;
  
  // position_slider 0 - 100
  double noFrame = position_slider*nbFrames / 100;
  
  // solution 1
  bool success = capture.set(CV_CAP_PROP_POS_FRAMES, noFrame);
  // solution 2
  double frameRate = capture.get(CV_CAP_PROP_FPS);
  double frameTime = 1000.0 * noFrame / frameRate;
  bool success = capture.set(CV_CAP_PROP_POS_MSEC, frameTime);
  
  if (!success) {
      std::cout << "Cannot set frame position from video file at " << noFrame << std::endl;       
      return;
  }
  
  currentPos = capture.get(CV_CAP_PROP_POS_FRAMES);
  if (currentPos != noFrame) {
      std::cout << "Requesting frame " << noFrame << " but current position == " << currentPos << std::endl;
  }
  
  success = capture.read(frame_aux);
  if (!success) {
      std::cout << "Cannot get frame from video file " << std::endl;
      return;
  }
  imshow("test", frame_aux);