ERCIM News No.48, January 2002 [contents]

Remote CAD Viewing.

Remote PC Applications on a PDA Device

by Charles Woodward and Petri Honkamaa

The Motion Vector Quantization (MVQ) method developed at VTT enables mobile operation of PC application software from a remote viewing unit. One of the first applications of the method is wireless viewing of 3D CAD models on a PDA device.

VTT has during the past years developed a strong video coding technology called MVQ (Motion Vector Quantization). The MVQ method is very light and fast at the receiving end, being especially well suited for implementation on low performance receiving devices and for low bitrate applications. The MVQ method is currently being licensed for international distribution by the companies Oplayo Oy (Finland) and ON-AIR A/S (Denmark).

Recently, the scope of video coding has been extended to new applications, ie, streaming moving imagery from computer sofware application’s display. The new XVQ (X Windows VQ) method enables users to operate practically any application running on a PC workstation from a remote display unit, such as a PDA device, linked to the computer over a mobile phone connection.

Remote 3D CAD Viewing
The XVQ development work was performed in co-operation with a Finnish CAD vendor, DeskArtes Oy, in the Intellivideo project. According to DeskArtes, mobile solutions for viewing of CAD files would bring significant time and cost savings to the production process by cutting short critical communication delays. DeskArtes provided to the project their View Expert software and programming work related to it, while all other work was done by VTT Information Technology.

For using the Wireless CAD Viewer, the user first establishes a GSM connection from his/her PDA device to a PC server workstation. The server program running on the workstation launches the View Expert software, supplies file browser information, and starts grabbing View Expert display area to be shown to the PDA user. With the available interaction commands, the client software lets the user rotate, zoom and pan, and ask for distances, angles and radii within the CAD model. Other CAD interaction commands will be straightforward to implement, as well.

The XVQ software is highly transparent: in effect, the user gets the feeling of operating straight with the CAD model as it would actually reside on the PDA device. The XVQ method requires much less memory and processing power compared to methods of (down)loading the CAD model locally on the PDA device. The method offers reasonable interaction speed with data transmission rates as low as 5-10 kbits/sec, while the CAD file size is limited only by the computing resources of the server machine.

Software Architecture
XVQ has been written in C (libraries) and in C++ (user interfaces). XVQServer runs under Windows and it can be used on any common PC workstation. XVQClient is currently implemented in the Windows CE environment and it is compiled for the Compaq iPAQ and Casio Cassiopeia devices. Future work includes implementation on other operating systems and platforms, such as laptop PCs and the Nokia Communicator.

XVQ Architecture.

The communication between the XVQServer and the XVQClient is made through a TCP/IP connection. Two sockets are used: one for streaming the MVQ-compressed application view from server to client, and the other for application specific control commands and info messages in ASCII form. High flexibility of the implementation is obtained by separating all the application-specific parts, like communication with the application and the client user interface, in dynamically loadable drivers.

General Applications
The usage of dynamic drivers makes it easy to develop XVQ remote operation solutions not only with CAD software but with any software that allows external control commands. The change of the external application can be made on the run, just by changing the drivers. And as the client user interface is also contained within the driver, the PDA view can always be optimised for the application in use.
At the date of writing, the VTT has already developed three further applications for XVQ: viewing the desktop area of the PC workstation, controlling and capturing the view from an external video camera, and remote control of a VCR device connected to the PC workstation. We look forward to extending the list of applications, the most suitable ones for implementation with XVQ being those characterised by large document/database size and/or lively graphic content.

Please contact:
Charles Woodward, VTT Information Technology
Tel: +358 9 4565629