Python OpenCV access webcam maximum resolution

Question

I am trying to acquire images from my webcam using a python code that imports OpenCV. The code is the following:

import sys
sys.path.append("C:\\opencv\\build\\python\\2.7")
import cv2
import cv2.cv as cv
import time

# Set resolution
cap = cv2.VideoCapture(0)
print "Frame default resolution: (" + str(cap.get(cv.CV_CAP_PROP_FRAME_WIDTH)) + "; " + str(cap.get(cv.CV_CAP_PROP_FRAME_HEIGHT)) + ")"
cap.set(cv.CV_CAP_PROP_FRAME_WIDTH, 800)
cap.set(cv.CV_CAP_PROP_FRAME_HEIGHT, 600)
print "Frame resolution set to: (" + str(cap.get(cv.CV_CAP_PROP_FRAME_WIDTH)) + "; " + str(cap.get(cv.CV_CAP_PROP_FRAME_HEIGHT)) + ")"

# Acquire frame
capture = cv.CreateCameraCapture(0)
img = cv.QueryFrame(capture)

The code works fine, except that the Camera default resolution is 640x480, and my code seems to be able to set only resolution values lower than that. For example, I can set the image size to 320x240, but I can't change it to 800x600. I have no error appearing: simply the resolution is set to the default one (640x480) as I try to set it to higher values.

The camera I am using (no other webcam is connected to the computer) is the QuickCam V-UBK45: with the software provided by Logitech, I am able to take pictures at full resolution (1280x960) and at all intermediate ones (e.g. 800x600).

Therefore, those frame sizes are supported from the hardware, but my code can't access them.

Does anyone know what I can do?

Answer 1

I used the different resolutions to set image resolution from List of common resolutions by looping over

def set_res(cap, x,y):
    cap.set(cv.CV_CAP_PROP_FRAME_WIDTH, int(x))
    cap.set(cv.CV_CAP_PROP_FRAME_HEIGHT, int(y))
    return str(cap.get(cv.CV_CAP_PROP_FRAME_WIDTH)),str(cap.get(cv.CV_CAP_PROP_FRAME_HEIGHT))

It seems that OpenCV or my camera allows only certain resolutions.

• 160.0 x 120.0

• 176.0 x 144.0

• 320.0 x 240.0

• 352.0 x 288.0

• 640.0 x 480.0

• 1024.0 x 768.0

• 1280.0 x 1024.0