Camera Connections

IEEE 1394 (Firewire)

Pros

• Simple daisy chaining capability

Cons

• Slower data transfer - up to 400Mbps/800Mbps
• No onboard memory for saving images
• Difficult to synchronize with other devices

GigE (Gigabit Ethernet)

Pros

• Faster transfer rates - up to 1000Mbps
• Can be deployed to remote network-connected locations

Cons

• Less triggering support
• Difficult to synchronize with other devices

USB 2.0

• Slower data transfer - up to 480Mbps

USB 3.0

• High speed, high pixel depth and large image file sizes
• Plug and play capability

PCA Dimension Reduction In Matlab

X = columnwise_vector';
%row-wise [X rows are the number of samples and cols are the number of dimensions]

C = mean(X);
X = X - repmat(C, size(X,1),1); %normalize by removing mean

covar = cov(X); %compute covariance matrix

[p,D]=eigs(covar, numDim);

X_reduced = (X*p);
X_reduced = X_reduced';

Hardware synchronizing a stereo rig of ps3 eye usb cameras

2 Links:

http://www.instructables.com/id/The-EyeWriter-20/?ALLSTEPS
http://nuigroup.com/forums/viewthread/12445/#66879

Viewing stereo usb cameras on ROS

Download and install the uvc_camera drivers

Edit the uvcCameraLaunch.launch to contain the following:

<!--xml-->

<launch>

      <node pkg="uvc_camera" type="stereo_node" name="uvc_camera_stereo">

        <param name="width" type="int" value="320" />

        <param name="height" type="int" value="240" />

        <param name="fps" type="int" value="30" />

        <param name="frame" type="string" value="wide_stereo" />

    <param name="right/device" type="string" value="/dev/video1" />

        <param name="left/device" type="string" value="/dev/video2" />

     </node>

</launch>

launch this stack by:  ROS_NAMESPACE=stereo roslaunch UAVcam uvcCameraLaunch.launch

View the published messages: rostopic list

make sure the ros_namespace precedes the /left and /right image stream messages.

To view each stream:

$ rosrun image_view image_view image:=/stereo/left/image_raw

$ rosrun image_view image_view image:=/stereo/right/image_raw 

If you have a built-in webcam, I disabled it using the following:

by adding "blacklist uvcvideo" to the end of the file /etc/modprobe.d/blacklist.conf

I made sure uvcvideo was the name of the driver being used for this webcam using hwinfo 

(you must restart for the webcam to be disabled)

Then run the camera_calibration.

http://www.ros.org/wiki/camera_calibration/Tutorials/StereoCalibration 

ps3 eye usb camera and ROS

How to work with playstation ps3 eye USB camera and ROS and OpenCV

http://siddhantahuja.wordpress.com/2011/07/20/working-with-ros-and-opencv-draft/

For stereo:
https://code.ros.org/gf/project/ros/mailman/?_forum_action=ForumMessageBrowse&thread_id=55017&action=ListThreads&mailman_id=20

roscd: command not found

Problem:
roscd: command not found

Solution:
To solve this problem you must define the source of the ros setup.bash file:
Execute:

- source /opt/ros/fuerte/setup.bash
- source ~/ros_workspace/setup.bash 

(the second one made all warnings go away - use this instead of the first one. With the first one, I still got some warnings when I typed roscd with no arguments) 

in a terminal. In my case I was working ROS Fuerte (version 1.8.10).

this happened because I didnt do the last steps of installing ROS.

For a permanent fix edit .bashrc (use 'gedit .bashrc" for editing)and add the following to the end of the file:

export ROS_WORKSPACE=/home/anubis/fuerte_workspace









notice that we changed the ros workspace name (from ros_workspace to fuerte_workspace)

Setting Mat Pixels (elements) in OpenCV

This is how you set individual element's color channels of a Mat structure in OpenCV

img.at<cv::Vec3b>(v,u)[0]=B;
img.at<cv::Vec3b>(v,u)[1]=G;
img.at<cv::Vec3b>(v,u)[2]=R;