1. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 1 Design and Evaluation of a Multi-User Virtual Audio Chat Lea Skorin-Kapov R&D Center, Ericsson Nikola Tesla, Zagreb, Croatia Maja Matijašević FER, University of Zagreb, Croatia

2. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 2 Presentation Outline Introduction Research issues Development of Virtual Audio Chat (VAC) Performance evaluation Conclusions

3. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 3 Introduction Virtual Reality (VR): interactive, immersive, multisensory, 3D synthetic environment VR service issues that dictate QoS requirements: –Rich VR/multimedia content –Perceived real-time interactivity –Multiple users Problem: different representations of QoS at user/application level and at communication level

4. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 4 Research has mainly progressed in two complementary directions: –Performance of virtual reality end systems –Virtual reality communications Limited research on relating user perceived system performance with quantitative network parameters in distributed VEs Our Goal: address relationship between network and application level parameters Interconnection model used for reference Research issues

5. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 5 Attempts to present common issues in different VR applications User view: seamless virtual world, composed of shared virtual objects and media streams (trans(ient) objects), and modified by simulation and/or user interactions Spatial composition: objects media components Distribution/synchronisation: replication of distributed objects and synchronisation for streams Media connectivity: different media profiles - mapping to transport level QoS parameters NVR Interconnection Model (1)

6. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 6 NVR Interconnection Model (2) Object UV Replication profile a v MC Media profile (QoS) Media connectivity (best effort) Stream mapping SharedObject Audio cont. Video cont. Text cont. Media container Geometry 3D graphics 2D graphics audiovideo text combined SC TransObject Data, graphics Replication Stream synchronization (inter-stream) Media synchronization (intra-stream) DS

7. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 7 Development of Virtual Audio Chat Audio conference with (desktop) virtual reality interface Three basic components: VRML mobile phone model Java applet opening RTP based audio conference –Java Media Framework (JMF) API used Modified Session Directory (sdr) tool – enables user to schedule and announce multimedia session

8. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 8 VRML mobile phone model

9. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 9 Virtual buffer Interaction with mobile keys Animation

10. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 10 Real-time data transfer using RTP/RTCP Application A Application B DecodingEncoding RTP RTCP UDP/IP (multicast) Figure adapted from Internet Protocols for Multimedia Communications, T. Braun, IEEE MultiMedia, 1997 Decoding Encoding RTP RTCP

11. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 11 Modified session directory (sdr) tool Sdr – scheduling/announcing multimedia sessions on the MBone Modified by enabling new media type: vrml_audio

12. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 12 VAC interconnection model graphics Replication DS MC Media connectivity SharedObject Geometry 3D graphics SC Profile 1 Stream synchronization (inter-stream) Profile 2 TransObject

13. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 13 Performance Evaluation RTP/RTCP packet throughput Interactivity –quantitative interactivity parameters Immersion –quantitative immersion parameters –jitter and packet loss

14. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 14 RTP/RTCP packet throughput

15. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 15 Interactivity Relating to scope and extend of user interactions in a VE Empirical approach using a questionnaire used to obtain user evaluation Can be quantified as combination of sensory support, navigation, and user representation Table 1. Quantitative interactivity parameters The keys on our mobile phone can be considered virtual controls. The tracking of user interactions refers to 2D pointer mouse Table 1. Quantitative interactivity parameters

16. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 16 Object selection and manipulation Interactions None (viewer)User appearance (avatar quality) Examine, fly, walkNavigation technique Pointer (2D) recognitionCommand input Mouse tracking Virtual controls Tracking ValueParameter Quantitative interactivity parameters

17. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 17 Immersion Presentation quality of (multi) sensory information that user perceives as a 3D synthetic environment Quantified as combination of visual, auditory, and haptic immersion No spatializationSound spatialization Phone quality (8000 Hz, 8 bit/sample) Sound quality ValueParameter Quantitative immersion parameters

18. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 18 Measurements of jitter and packet loss using rtpmon tool – reads RTCP packets generated by users

19. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 19 Conclusions A simple multi-user interactive VR/Web application has been designed and developed The overall approach, from model to implementation, is general and may be applied to a wide range of virtual reality applications Performance results may be used for application improvements (as perceived by the user) as well as for resource reservation

20. TERENA NETWORKING CONFERENCE 2002 03. - 06.2002., Limerick Ireland 20 DEMO!