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Design and Evaluation of a Multi-User Virtual Audio Chat

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. Presentation Outline. Introduction Research issues Development of Virtual Audio Chat (VAC)

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Design and Evaluation of a Multi-User Virtual Audio Chat

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  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. Presentation Outline • Introduction • Research issues • Development of Virtual Audio Chat (VAC) • Performance evaluation • Conclusions

  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. Research issues • 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

  5. NVR Interconnection Model (1) • 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

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

  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. VRML mobile phone model

  9. Interaction with mobile keys Virtual buffer Animation

  10. Real-time data transfer using RTP/RTCP Application A Application B Decoding Decoding Encoding Encoding RTP RTCP RTCP RTP UDP/IP (multicast) Figure adapted from “Internet Protocols for Multimedia Communications”, T. Braun , IEEE MultiMedia, 1997

  11. Modified session directory (sdr) tool • Sdr – scheduling/announcing multimedia sessions on the MBone • Modified by enabling new media type: vrml_audio

  12. TransObject Stream synchronization (inter-stream) Profile 2 VAC interconnection model SharedObject Geometry 3D graphics SC graphics Replication DS Profile 1 MC Media connectivity

  13. Performance Evaluation • RTP/RTCP packet throughput • Interactivity • quantitative interactivity parameters • Immersion • quantitative immersion parameters • jitter and packet loss

  14. RTP/RTCP packet throughput

  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. Parameter Value Tracking Mouse tracking Virtual controls Command input Pointer (2D) recognition Navigation technique Examine, fly, walk User appearance (avatar quality) None (viewer) Interactions Object selection and manipulation Quantitative interactivity parameters

  17. Parameter Value Sound quality Phone quality     (8000 Hz, 8 bit/sample) Sound spatialization No spatialization Immersion • Presentation quality of (multi) sensory information that user perceives as a 3D synthetic environment • Quantified as combination of visual, auditory, and haptic immersion Quantitative immersion parameters

  18. Measurements of jitter and packet loss using rtpmon tool – reads RTCP packets generated by users

  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. DEMO!

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