SyncCast: Synchronized Dissemination in Multi-site Interactive 3D Tele-immersion

Transcription

1 Syncast: Synchronized issemination in Multi-site Interactive 3 Tele-immersion Zixia Huang, W. Wu, K. Nahrstedt, R. Rivas and. refin epartment of omputer Science University of Illinois at Urbana-hampaign {zhuang21, wwu23, klara, trivas, illinois.edu

2 Tele-immersive Environment Photo courtesy of Prof. Ruzena Bajcsy.

3 Multi-site 3TI ommunication Purdue U Berkeley U avis UIU service gateway display camera audio in/out

4 Multi-site 3TI ommunication Purdue intermediate site U Berkeley UIU sender receiver U avis

5 P1: elay and Bandwidth onstraint Purdue UIU 5 ms 36 ms U Berkeley 11 ms 1. elay constraint: interactivity 2. Bandwidth constraint U avis

6 P2: Inter-receiver Sync Skew Purdue UIU 5 ms 36 ms U Berkeley 11 ms U avis Inter-receiver sync skew: Max EE min EE = 42 ms

7 P3: Inter-sender Sync Skew Purdue 5 ms 36 ms U Berkeley UIU 11 ms U avis Inter-sender sync skew: y Max EE min EE = 42 ms

8 P4: Inter-stream Sync Skew Purdue 37 ms U Berkeley UIU 5 ms 11 ms 36 ms U avis Inter-stream sync skew: Max EE min EE = 4 ms Inter-video skew udio-visual skew

9 Inter-stream Sync Skew Video multi-stream synchronization udio-visual synchronization video dominant stream (S) ( ) (largest visual contribution)

10 Problem Statement Previous work did not study all synchronization constraints! We want to design a multi-site 3TI dissemination scheme that minimizes EE with synchronization and bandwidth constraints. Interactivity EE decides the interactivity Minimize EE for dissemination paths Synchronization onstraint Inter-stream sync: inter-video and audio-visual Inter-site sync: inter-sender and inter-receiver Bandwidth onstraint Inbound bandwidth Outbound bandwidth

11 What we consider Stream prioritization ifferent visual contribution Path prioritization Latency vs. fairness Other heuristics at sender site Bandwidth preservation policy

12 Stream Prioritization o 3 Free Viewpoint ontribution Factor (F): O F(vs) Ovs O vs video stream u Renderer ominant Stream (S): the video stream with the largest F to user view Non-dominant stream (NS): F > 0 O u There is a video S for each sender-receiver pair. Yang et al, multi-stream adaptation framework for bandwidth management in 3 tele-immersion, M NOSSV 2006

13 Stream Prioritization Priority is given to streams with greater visual contributions. We divide all streams into two service classes (S). 1 issemination i of all audio and video S Prioritized stream queue at UK: S1 = {S1(IL), S1(), S2(E)} SN RV S (F) UK S1 (.8) UK IL S1 (.9) UK E S2 (.8)

14 Stream Prioritization o Priority is given to streams with greater visual contributions. We divide all streams into two service classes (S). 1 issemination of all audio and video S 2 issemination of all video NS Prioritized stream queue at UK: S1 = {S1(IL), S1(), S2(E)} S2 = {S2(), S2(IL), S1(E), S3(E), S3()} SN RV S (F) NS (F) UK S1 (.8) S2 (.4), S3 (.1) UK IL S1 (.9) S2 (.4) UK E S2 (.8) S1 (.3), S3 (.3)

15 Path Prioritization stream from a sender site to a receiver can follow multiple li l paths Latency: EE between the sender and receiver 3 paths for S3 from UK to E: (1) UK -> E 18 ms (2) UK -> IL -> E 147 ms (3) UK -> -> E 168 ms SN RV S NS UK S1 S2, S3 UK IL S1 S2 UK E S2 S1,S3

16 Path Prioritization stream from a sender site to a receiver can follow multiple li l paths Latency: EE between the sender and receiver Unfairness (Q): number of sites on the path which does not request a stream as S or NS 3pathsforS3fromUKtoE: from to (1) UK -> E 18 ms (Q = 0) (2) () UK -> IL -> E 147 ms (Q = 1) (3) UK -> -> E 168 ms (Q = 0) SN RV S NS UK S1 S2, S3 UK IL S1 S2 UK E S2 S1,S3

17 Path Prioritization stream from a sender site to a receiver can follow multiple paths Latency: EE between the sender and receiver Unfairness (Q): number of sites on the path which does not request a stream as S or NS Our policy: fairness first, latency next (to preserve bandwidth) 3pathsforS3fromUKtoE: from to (1) UK -> E 18 ms (Q = 0) (2) UK -> -> E 168 ms (Q = 0) (3) UK -> IL -> E 147 ms (Q = 1) SN RV S NS UK S1 S2, S3 UK IL S1 S2 UK E S2 S1,S3

18 Path Prioritization stream from a sender site to a receiver can follow multiple paths Latency: EE between the sender and receiver Unfairness (Q): number of sites on the path which does not request a stream as S or NS Our policy: fairness first, latency next (to preserve bandwidth) Other heuristics: a sender site ONLY relays other senders S 3pathsforS3fromUKtoE: from to (1) UK -> E 18 ms (Q = 0) (2) UK -> -> E 168 ms (Q = 0) (3) UK -> IL -> E 147 ms (Q = 1) If is also a sender site

19 Path EE and Synchronization Skews EE of S paths decide the inter-sender/inter-receiver skews Video S have the greatest visual contributions Video S are given the top priority in dissemination Video NS may not arrive at the receivers Inter-stream skews are decided by EE of both S and NS paths ZERO audio-visual skew (audio and video S same path) Inter-video synchronized at the receiver jitter buffer of a fixed size throughout the system

20 Syncast esign (Initialization) Stream Prioritization Path Prioritization 1. Stream Prioritization 2. Path Prioritization 3. onstraint Setup Max BW_in = 3streams Max BW_out = 3 streams Max inter-stream skew = 50 ms Max inter-site skew = 50 ms

21 Syncast esign (S issemination) Stream Path S1: S Prioritization Prioritization isseminationi i S Tree onstruction Pi Prioritized iti stream queue at tuk: S1 = {S1(IL), S1(), S2(E)} S1: UK -> IL (80) S1: UK -> (72) S2: UK -> E (18) SN RV S (F) UK S1 (.8) UK IL S1 (.9) UK E S2 (.8)

22 Syncast esign (S issemination) Stream Path S1: S Prioritization Prioritization isseminationi i S Tree onstruction Pi Prioritized iti stream queue at tuk: S1 = {S1(IL), S1(), S2(E)} S1: UK -> IL (80) S1: UK -> (72) S2: UK -> E (18) SN RV S (F) UK S1 (.8) UK IL S1 (.9) UK E S2 (.8) Inter-receiver sync skew! ( )

23 Syncast esign (S issemination) Stream Path S1: S Prioritization Prioritization isseminationi i S Tree onstruction Pi Prioritized iti stream queue at tuk: S1 = {S1(IL), S1(), S2(E)} S1: UK -> IL (80) S1: UK -> (72) S2: UK -> E (18) S2: UK -> IL -> E (147) S2: UK -> -> E (168) S2: UK -> E (18) Inter-receiver sync Inter-receiver sync SN RV S (F) UK S1 (.8) Inter-receiver sync UK IL S1 (.9) and is a sender UK E S2 (.8)

24 Syncast esign (S issemination) Stream Path S1: S Prioritization Prioritization isseminationi i S Tree onstruction S Tree djustment Prioritized stream queue at UK: S1 = {S1(IL), S1(), S2(E)} S1: :U UK -> IL (80) S1: UK -> (72) S2: UK -> E (18) Find alternative path for UK->IL: NOT POSSIBLE! Violate Sync onstraint: Introduce latency at the receiver for S2: UK->E SN RV S (F) UK S1 (.8) UK IL S1 (.9) UK E S2 (.8)

25 Syncast esign (NS issemination) Stream Path S1: S S2: NS Pi Prioritization ii i Pi Prioritization ii i issemination isseminationi Select a parent node which is either a sender site or a site has received the stream with synchronization and bandwidth constraints Try to reduce the case when the sender directly sends a NS to a receiver in order to save the sender bandwidth Prioritized stream queue at UK: S2 = {S2(), S2(IL), S1(E), S3(E), S3()} SN RV S NS S2: UK->E-> (106) S2: UK->E->IL (92) S1: No Path (UK, E) inter-stream skew & BW S3: No Path (UK, E) BW constraints S3: No Path (UK, ) BW constraints UK S1 S2, S3 UK IL S1 S2 UK E S2 S1,S3S3

26 Syncast esign MORE ETILS? PLS REFER TO THE PPER! Si k BW Initialization w Sync Skew

27 Experiment Setup Internet delays are collected from PlanetLab nodes overing 3 continents: sia, mericas, Europe Firewall issues and poor links are considered 5-node (2 senders) and 9-node (4 senders) configurations Half of nodes are senders Each sender outputs 8 streams (1 S and 2 NS) User view diversity 50% of the receiver sites share the same video S nother 50% of the receiver sites share different S

28 We compare Syncast with Viewast Syncast Viewast elay Minimize delay elay bound Bandwidth BW bound BW bound PathFi Fairness Yes No Inter-stream skew Yes No Inter-sender skew Yes No Inter-receiver receiver skew Yes No Z. YN, W.WU, K. NHRSTET,. KURILLO, R. BJSY, Enabling Multi-party 3 Tele-immersive Environments with Viewast, M TOMP, 2009.

29 ifferent network environment (ms) Network ase: 5 Network ase: 5E IL E JP N IL E JP N IL UK E NY IL UK E NY

30 Experiment Results (Syncast vs Viewast) Syncast (blue line) consistently bounds the inter-stream skew. Viewast (red line) has greater variations Inter-sender/Inter-receiver skew bound for Syncast y elay bound for Viewast

31 Experiment Results (Syncast vs Viewast) Syncast (blue line) consistently bounds the inter-sender and inter-receiver skew, and is more reliable than Viewast results. Inter-sender/Inter-receiver skew bound for Syncast elay bound for Viewast

32 onclusions We propose Syncast used for multi-site synchronization oncept of stream service class Path selection algorithm to improve fairness Multicast tree (forest) construction Bound inter-stream and inter-site synchronization Evaluation using PlanetLab real Internet data