please repeat your attempt and in an other shell run rostopic list -v and show us the output.

output is: Published topics: * /rosout [rosgraph_msgs/Log] 2 publishers * /rosout_agg [rosgraph_msgs/Log] 1 publisher

Subscribed topics: * /my_stereo_cam/disparity [stereo_msgs/DisparityImage] 1 subscriber * /my_stereo_cam/right/image_rect_color [sensor_msgs/Image] 1 subscriber

continued: * /rosout [rosgraph_msgs/Log] 1 subscriber * /my_stereo_cam/left/image_rect_color [sensor_msgs/Image] 1 subscriber

clearly you have no topics with your camera data published. you can not just plugin a usb camera and it will work, you need some ROS node that will read the camera data and publish this data on ROS topics. What kind of ROS node (and whether it exists) depends on the cameras.

Can you describe your setup? What cameras are you using?

i am using normal usb web cam "Quantum 25 mp webcam". i previously used launch file of "usb_cam-develop" package to take the video feed , but it supports only one camera at a time.I also tried with "uvc_camera" launch file "stereo_node.launch " but it didn't worked out.

it's hard to determine what your problem is. perhaps having a look at http://wiki.ros.org/libuvc_camera helps.

also note that you first need to get the images and CameraInfo of both webcams separately into ROS. Only after using http://wiki.ros.org/camera_calibration/Tutorials/StereoCalibration you make a stereo pair out of your webcams.

can you tell me a way by which i can use both of my usb cameras at the same time? bcoz to use camera_calibration driver it is required to publish left and right images over ROS.

I never tried that myself and I see no obvious explanation in the documentation. Perhaps open a new question asking that?

Exactly, there is no documentation neither seen any tutorial which explains you to do so. Yup I an going open a new question.