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POPython OpenCV stereo cam blind one?
 

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  1. POPython OpenCV stereo cam blind one?
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    <p>My system is Linux HPDebian 3.2.0-2-amd64 #1 SMP x86_64 GNU/Linux Python 2.7, OpenCV2. I can use only 1 cam. </p> <p>My question is How to get a video feed from 2 cams? I had read C++ version but I prefer python. It is easier for non-programmer.</p> <p>I don't understand why my webcam works only Wleft, but WRight is blank-gray windows. And at the command line </p> <blockquote> <p>VIDIOC_QBUF: Invalid argument </p> </blockquote> <p>continue to flood my command line.</p> <p>OpenCV-Python has a ready-made package of stereo program, but I need to access the elements of each cam because I want to test my algorithm.</p> <p>My attempt:</p> <pre><code>''' Simple Stereo feed ''' import cv cv.NamedWindow("wLeft", cv.CV_WINDOW_AUTOSIZE) cv.NamedWindow("wRight", cv.CV_WINDOW_AUTOSIZE) captureL = cv.CaptureFromCAM(0) captureR = cv.CaptureFromCAM(1) def repeat(): frameL = cv.QueryFrame(captureL) cv.ShowImage("wLeft", frameL) frameR = cv.QueryFrame(captureR) cv.ShowImage("wRight", frameR) while True: repeat() if cv.WaitKey(33)==27: break cv.DestroyAllWindows() </code></pre> <h2>Update 1</h2> <p>Answer to your questions:</p> <ol> <li>In current OpenCV-Python. I can not find any command, but I when I comment out the Leftcam, Rightcam works. And vice versa.</li> <li><p>Yes, I just found it!. I redirected command and carefully searched.</p> <blockquote> <p>libv4l2: error turning on stream: No space left on device</p> </blockquote></li> <li><p>They are identical. OKER193.</p></li> <li>I can use it just only 1 cam Left or Right only. Can not get a video feed from two of them simulataneously.</li> <li><p>I have no hubs. I don't know it is a real port or not, but I connect it left and right of my notebook.</p> <p><a href="http://opencv-users.1802565.n2.nabble.com/Multiple-Camera-Read-Error-td7001563.html" rel="nofollow noreferrer">http://opencv-users.1802565.n2.nabble.com/Multiple-Camera-Read-Error-td7001563.html</a></p></li> </ol> <p>I tried cv.ReleaseCapture()</p> <pre><code>def repeat(): frameL = cv.QueryFrame(captureL) cv.ShowImage("wLeft", frameL) cv.ReleaseCapture(captureL) frameR = cv.QueryFrame(captureR) cv.ShowImage("wRight", frameR) cv.ReleaseCapture(captureR) </code></pre> <p>I got the errors:</p> <pre><code>... VIDIOC_QUERYMENU: Invalid argument //Many lines ... Traceback (most recent call last): File "55.py", line 19, in &lt;module&gt; repeat() File "55.py", line 13, in repeat cv.ReleaseCapture(captureL) AttributeError: 'module' object has no attribute 'ReleaseCapture' </code></pre> <p>I really wonder <br><a href="http://opencv.willowgarage.com/documentation/python/highgui_reading_and_writing_images_and_video.html?highlight=releasecapture" rel="nofollow noreferrer">http://opencv.willowgarage.com/documentation/python/highgui_reading_and_writing_images_and_video.html?highlight=releasecapture</a><br> CaptureFromCAM last line say To release the structure, use ReleaseCapture. This function may be dropped out.</p> <p>Wandering around and found this <br><a href="https://superuser.com/questions/431759/using-multiple-usb-webcams-in-linux" title="this">https://superuser.com/questions/431759/using-multiple-usb-webcams-in-linux</a><br></p> <p>Then I check my resolution per cam is 640x480 as a normal. And my webcam is 1.1/2.0 USB interface.</p> <pre><code>root@HPDebian:~# v4l2-ctl -d /dev/video0 --list-formats ioctl: VIDIOC_ENUM_FMT Index : 0 Type : Video Capture Pixel Format: 'YUYV' Name : YUV 4:2:2 (YUYV) </code></pre> <p>Then check another cam</p> <pre><code>root@HPDebian:~# v4l2-ctl -d /dev/video1 --list-formats ioctl: VIDIOC_ENUM_FMT Index : 0 Type : Video Capture Pixel Format: 'YUYV' Name : YUV 4:2:2 (YUYV) </code></pre> <p>At this point I am not sure about my USB notebook. It may be a hub inside. I will try reduce the resolution and post my result again.</p> <h2>Update 2</h2> <p>Try time.sleep(1) from Martin:</p> <pre><code>VIDIOC_QUERYMENU: Invalid argument //Many lines libv4l2: error setting pixformat: Device or resource busy HIGHGUI ERROR: libv4l unable to ioctl S_FMT libv4l2: error setting pixformat: Device or resource busy libv4l1: error setting pixformat: Device or resource busy HIGHGUI ERROR: libv4l unable to ioctl VIDIOCSPICT libv4l2: error turning on stream: No space left on device VIDIOC_STREAMON: No space left on device VIDIOC_QBUF: Invalid argument //Many lines until Ctrl C </code></pre> <p>I will try this again in M$ xp.</p> <h2>Update 3</h2> <p>Still using Linux. M$ xp is busy. This time I del the c1 and c2. Since I don't know how to release camera. I believe that API of driver I use is allow only 1 device access kernel per time. So I try this one.</p> <pre><code>def repeat1(): c1 = cv.CreateCameraCapture(0) i1 = cv.QueryFrame(c1) cv.ShowImage("WebCAM1", i1) del(c1) def repeat2(): c2 = cv.CreateCameraCapture(1) i2 = cv.QueryFrame(c2) cv.ShowImage("WebCAM2", i2) del(c2) </code></pre> <p>Program run very sluggish and WebCAM1 is distorted, WebCAM2 is not.</p>
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    1. COSeems like you're not the only one experiencing this: http://permalink.gmane.org/gmane.comp.lib.opencv.user/263
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    2. COpossible duplicate of [OpenCV with 2 cameras VC++](http://stackoverflow.com/questions/10194033/opencv-with-2-cameras-vc)
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    3. COHave you tried "import cv2" and "CaputureL = video.create_capture(0)"? Also you should probably release your cameras at the break with "CaputureL.release()" as this could lead to problems while debugging.
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