Remote Demos

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. Participant’s Desk top Participant’s Desk top Participant’s Desk top Participant’s Desk top Operational View Speaker’s Desk top 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 > 115.2 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 • Interruptions • Interaction • Resolution • Telephone • Overlay voice on slides • Fixed • Voice packets • Delays • Fixed • Variable • Experiment • Bandwidth requirements Remote Demo