[Bug 321358] [NEW] v4l2 image capture doesn't work

[Ethan Townsend]

Public bug reported:

Binary package hint: libcv-dev

using libcv-dev and libcv1 version 1.0.0-6.1 on kubuntu 8.10 amd64.

trying to initialize v4l2 via the demo programs (in c or python) fails with "Could not initialize capturing..." for the c programs or 
"Error opening capture device" for python programs.  The demo programs that did not involve webcam capture work as expected.  /dev/video0 exists and works with cheese, skype, etc.  I tried 2 webcams, one was a logitech with the following output from v4l-info

>### v4l2 device info [/dev/video0] ###
>general info                          
>    VIDIOC_QUERYCAP                   
>        driver                  : "zc3xx"
>        card                    : "USB Camera (046d:08d7)"
>        bus_info                : "0000:00:02.0"          
>        version                 : 2.2.0                   
>        capabilities            : 0x5000001 [VIDEO_CAPTURE,READWRITE,STREAMING]

and dmesg output
>[21413.628051] usb 1-7: new full speed USB device using ohci_hcd and address 8
>[21413.833749] usb 1-7: configuration #1 chosen from 1 choice
>[21413.837178] gspca: probing 046d:08d7
>[21415.711809] zc3xx: probe 2wr ov vga 0x0000
>[21415.783806] zc3xx: probe sensor -> 11
>[21415.783819] zc3xx: Find Sensor HV7131R(c)
>[21415.805489] gspca: probe ok
>[21415.807305] gspca: probing 046d:08d7

and one creative labs webcam with this output:

>### v4l2 device info [/dev/video0] ###
>general info                          
>    VIDIOC_QUERYCAP                   
>        driver                  : "zc3xx"
>        card                    : "USB Camera (041e:401c)"
>        bus_info                : "0000:00:02.0"          
>        version                 : 2.2.0                   
>        capabilities            : 0x5000001 [VIDEO_CAPTURE,READWRITE,STREAMING]

Both produced identical results with opencv.

I also tried running this python script:

>import pygame
>import Image
>from pygame.locals import *
>import sys
>
>import opencv
>#this is important for capturing/displaying images
>from opencv import highgui 
>
>camera = highgui.cvCreateCameraCapture(0)
>def get_image():
>    im = highgui.cvQueryFrame(camera)
>    # Add the line below if you need it (Ubuntu 8.04+)
>    im = opencv.cvGetMat(im)
>    #convert Ipl image to PIL image
>    return opencv.adaptors.Ipl2PIL(im) 
>
>fps = 30.0
>pygame.init()
>window = pygame.display.set_mode((640,480))
>pygame.display.set_caption("WebCam Demo")
>screen = pygame.display.get_surface()
>
>while True:
>    events = pygame.event.get()
>    for event in events:
>        if event.type == QUIT or event.type == KEYDOWN:
>            sys.exit(0)
>    im = get_image()
>    pg_img = pygame.image.frombuffer(im.tostring(), im.size, im.mode)
>    screen.blit(pg_img, (0,0))
>    pygame.display.flip()
>    pygame.time.delay(int(1000 * 1.0/fps))

This script fails with the following output:

>Traceback (most recent call last):
>  File "test.py", line 29, in <module>
>    im = get_image()
>  File "test.py", line 14, in get_image
>    im = opencv.cvGetMat(im)
>  File "/var/lib/python-support/python2.5/opencv/cv.py", line 3826, in cvGetMat
>    return _cv.cvGetMat(*args)
>RuntimeError:  openCV Error:
>        Status=Null pointer
>        function name=cvGetMat
>        error message=NULL array pointer is passed
>        file_name=cxarray.cpp
>        line=2780

I am new with v4l2 and opencv, I apologize if this bug should be filed
under the zc3xx/gspca drivers, I have no way to test other webcam
modules.

** Affects: opencv (Ubuntu)
     Importance: Undecided
         Status: New

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v4l2 image capture doesn't work
https://bugs.launchpad.net/bugs/321358
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