Cannot open 2 USB cameras simultaneously on VLC player Ubuntu 12.04

How I open a Camera:
In terminal (text after the $ prompt = commands that I type):

$ ls /dev/video*

/dev/video0  /dev/video1

$ vlc v4l2:///dev/video0

VLC media player 2.0.8 Twoflower (revision 2.0.8a-0-g68cf50b)

[0x9f2d908] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.

Now, VLC starts playing camera output.

In another new terminal (text after the $ prompt = commands that I type):

$ vlc v4l2:///dev/video1

VLC media player 2.0.8 Twoflower (revision 2.0.8a-0-g68cf50b)

[0x9b24908] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.

[0xb0500960] v4l2 demux error: VIDIOC_STREAMON failed

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

libv4l2: error setting pixformat: Device or resource busy

[0xb0501188] v4l2 access error: cannot set input 0: Device or resource busy

[0xb0501188] v4l2 access error: cannot set input 0: Device or resource busy

[0xb5300618] main input error: open of `v4l2:///dev/video1' failed

No video is played in this terminal's VLC window.

Primary Objective: I want to open two cameras simultaneously in opencv (c++) ... got similar errors with opencv .. so I'm using VLC Player to debug the issue.
The errors when opening two cameras simultaneously using c++ opencv ( the code is similar to https://code.ros.org/trac/opencv/browser/trunk/opencv/samples/cpp/starter_video.cpp?rev=4705 )

e557822@e557822-T740:~/Desktop/Camera/starter_video2$ ls /dev/video*

/dev/video0  /dev/video1  /dev/video2

e557822@e557822-T740:~/Desktop/Camera/starter_video2$ ./starter_video2 0 1

VIDIOC_QUERYMENU: Invalid argument

VIDIOC_QUERYMENU: Invalid argument

VIDIOC_QUERYMENU: Invalid argument

VIDIOC_QUERYMENU: Invalid argument

VIDIOC_QUERYMENU: Invalid argument

VIDIOC_QUERYMENU: Invalid argument

VIDIOC_QUERYMENU: Invalid argument

press space to save a picture. q or esc to quit

init done 

opengl support available 

libv4l2: error turning on stream: No space left on device

VIDIOC_STREAMON: No space left on device