Capture from 2 cameras (OpenCV, Python)

Question

So, I'm trying to capture from two cameras in openCV (python and windows 7). I shoot with one camera just fine, you will also notice that I make some funky for the image, but it does not matter. This is a code that tries to use two

import cv import time cv.NamedWindow("camera", 1) cv.NamedWindow("camera2", 1) capture = cv.CaptureFromCAM(0) capture2 = cv.CaptureFromCAM(1) while True: img = cv.GetMat(cv.QueryFrame(capture)) img2 = cv.GetMat(cv.QueryFrame(capture2)) dst_image = cv.CloneMat(img) dst_image2 = cv.CloneMat(img2) cv.ConvertScale(img, dst_image, 255, -59745.0) cv.ConvertScale(img2, dst_image2, 255, -59745.0) cv.ShowImage("camera", dst_image) cv.ShowImage("camera2", dst_image2) if cv.WaitKey(10) == 27: cv.DestroyWindow("camera") cv.DestroyWindow("camera2") break 

Rather simple. However, this will not work. When trying to create a matrix from the second camera (the second line of code in the loop), I was told that the capture is zero. The cameras I use are logitech and are the same model.

Side note: I also could not find the command to count the cameras connected to the python, so if someone could refer to me, I would really appreciate it. --Ashley

EDIT: It may also be useful to know that windows often prompt me to choose which camera I would like to use. I cannot avoid this behavior. In addition, I downloaded some security, such as software that successfully starts both cameras at the same time. This is not an open source or anything like that. So clearly, it is possible.

Answer 1

I had the same issue with two webcams with the lifecam website. After a little reading, I think the problem is with bandwidth overload on the USB bus. Both cameras started working if I 1.) lower the resolution (320 x 240 each) or 2.) lower the frame rate (~ 99 ms at 800 x 600). Attached code I received:

 import cv cv.NamedWindow("Camera 1") cv.NamedWindow("Camera 2") video1 = cv.CaptureFromCAM(0) cv.SetCaptureProperty(video1, cv.CV_CAP_PROP_FRAME_WIDTH, 800) cv.SetCaptureProperty(video1, cv.CV_CAP_PROP_FRAME_HEIGHT, 600) video2 = cv.CaptureFromCAM(1) cv.SetCaptureProperty(video2, cv.CV_CAP_PROP_FRAME_WIDTH, 800) cv.SetCaptureProperty(video2, cv.CV_CAP_PROP_FRAME_HEIGHT, 600) loop = True while(loop == True): frame1 = cv.QueryFrame(video1) frame2 = cv.QueryFrame(video2) cv.ShowImage("Camera 1", frame1) cv.ShowImage("Camera 2", frame2) char = cv.WaitKey(99) if (char == 27): loop = False cv.DestroyWindow("Camera 1") cv.DestroyWindow("Camera 2") 

Answer 2

here is a little code:

 import VideoCapture cam0 = VideoCapture.Device(0) cam1 = VideoCapture.Device(1) im0 = cam0.getImage() im1 = cam1.getImage() 

im0 and im1 are PIL images. Now you can use scipy to convert it to arrays as follows:

 import scipy as sp imarray0 = asarray(im0) imarray1 = asarray(im1) 

imarray0 and imarray1 are multi-dimensional 2D arrays that you can use with openCV functions.

Answer 3

If you use windows for coding, why don't you try the VideoCapture module. It is very easy to use and gives a PIL image as an output. You can change it to a 2D array later.