Proposal of new ROS package for virtual camera to advertise camera_info, image and point cloud

[Kentaro Wada]

For testing and analyzing for vision ROS nodes, it is useful if we have virtual camera driver to advertise camera_info, image and point cloud.

Because rosbag play --loop does not work well on some situations, and we sometimes would like to use one moment of camera view continuously on analyzing.

The first motivation is to advertise camera_info with synchronization with image and point cloud.

There are already node to publish point cloud from pcd file,

- pcl_ros/pcd_to_pointcloud: https://github.com/ros-perception/perception_pcl/blob/kinetic-devel/pcl_ros/tools/pcd_to_pointcloud.cpp

and image from image file.

- image_publisher/image_publisher: https://github.com/ros-perception/image_pipeline/blob/indigo/image_publisher/src/nodelet/image_publisher_nodelet.cpp

To advertise camera_info, adding feature to publish it to pcd_to_pointcloud is a solution. (image_publisher already has this feature using ~camera_info_url rosparam)

But it does not solve the problem of synchronization between the image and pointcloud,

and it is also a problem that topic saving utilities for image and pointcloud are dispersed (pcl_ros/pointcloud_to_pcd, image_view/image_saver).

One for camera_info does not exist as far as I know.

In this post, I propose to create a new ROS package to serve the feature of advertise camera_info, image, and point cloud,

and saving utilities for them. Ideally, it can be placed as ros-drivers/virtual_camera.

This is firstly suggested in https://github.com/ros-perception/image_common/pull/54#issuecomment-248328918 .

And most implementation is done in https://github.com/jsk-ros-pkg/jsk_recognition/pull/1884.

If this package is regarded as useful enough to be added to ros-drivers, it will be added there on GitHub.

Anyone who have some idea on this?

[Jack O'Quin]

The normal ROS solution for storing these data with synchronized time stamps is using rosbag. 

Wouldn't the PCD and image files lose relative timing information?  

--

 joq

[Kentaro Wada]

I'm thinking save the PCD and image files with timestamp in their filename.

A solution is adding an option --increment-loop to publish topics with incremental timestamp replacing.

rosbag play --start=TIME1 --end=TIME2 --increment-loop

and this differs from --loop that the timestamp does not go backward.

rosbag play --start=TIME1 --end=TIME1 --increment-loop

to publish topics like virtual_camera at a time TIME1.