1. Remote Demos
Remote Demo

2. Elements of the Problem
Conference call – single speaker, several participants
Demo using the internet
Telephone for voice support
VoIP
One person is showing the demo
Others can ask question
Each step of the demo should be easily visible
Mouse movements must be tracked
Mouse generates data at about 20 bytes per second
Keyboards generate data at about 10 bytes per second
Interaction with audience
Reuse by audience
Remote Demo

3. Operational View Participant’s Desk top Participant’s Speaker’s
Remote Demo

4. Real MM problems
The Remote Demos problem is an abstraction of several real MM problems
Video on demand: Similar to off-line retrieval of demo info.
E-learning: S.G. Deshpande and J.N.Hwang, “A real-time interactive virtual classroom multimedia distance learning system”, IEEE Trans on Multimedia, Dec 2001.
Remote Demo

5. Elements of the Problem - 2
Speaker opens a window for showing the demo / presentation
Speaker uses the telephone link to describe what the participants are seeing
Analog or digital telephone
VoIP implements digital telephone
Participant questions can be handled in several ways
Chat, instant messaging
Voice channel alerts
Remote Demo

6. How Would You Build the Remote Demo Capability?
What goes on in the background?
What are the constraints?
Remote Demo

7. Possible Approach - 1 Speaker’s side
Capture the contents in the active window every few (say 100) milliseconds
View as a 2-D representation (a matrix)
Each pixel will be 3 element vector – RGB
24 bits per pixel
Window size?
Would like 1024 x768, but let us start with a smaller window
Save this data in a file using a browser compatible image format – gif, jpeg,…
You need a web server
What about voice?
Remote Demo

8. Possible Approach - 2 Participant’s desk top Opens a browser
Use specified URL
Answers questions like
What type of connection are you using?
Downloads an applet
Refresh the screen every x seconds
Remote Demo

9. What Are the Potential Problems?
Volume of data
For a window size of 800 x 600 the data transferred every x seconds is
800 * 600 * 3 = 1.44 MB
If x = .1 then bandwidth required will be
> Mbps !!!!!
Possible solutions –
Reduce active window size – ugh!!
Increase x – discontinuous motion – where is the cursor?
Remote Demo

10. MM Specialist Approach
Use JPEG to compress the screen capture image
Use PCM to encode voice – data volume is much less but quality requirements are stringent
Consecutive images do not have much change – often just the cursor movement
Transmit only the changes from the previous transmission
Result
When a new screen comes up, it will take a little time
For a particular screen the cursor motion will appear to be almost continuous
Your Assignment Build a Remote Demo System
Remote Demo

11. Assignment Use a phased approach
Phase I develop a solution as a typical computer programmer
After testing and demonstrating the working of Phase I, search for compression algorithms that are based on detecting change.
Differential Pulse Code Modulation (DPCM) is one such algorithm. However to get the biggest bang you will also need to look at Run Length Encoding and Huffman coding algorithms.
Phase II augment Phase I to include the IP Specialist approach
Remote Demo

12. Simplified Demo for the Assignment
Client’s browser
Speaker’s Window
Internet connection
Remote Demo

13. What about voice? Multiple speakers Telephone Overlay voice on slides
Interruptions
Interaction
Resolution
Telephone
Overlay voice on slides
Fixed
Voice packets
Delays
Variable
Experiment
Bandwidth requirements
Remote Demo