VCR-oriented Video Broadcasting for Near Video-On-Demand Services

1. VCR-oriented Video Broadcasting for Near Video-On-Demand Services Jin B. Kwon and Heon Y. Yeon Appears in IEEE Transactions on Consumer Electronics, vol. 49, No. 4, Nov. 2003, pp. 1106 - 1113

2. Outline • Introduction • Conditions for continuous VCR • VCR-oriented periodic broadcasting (VPB) • Reception schedule for continuous VCR actions • Discontinuous VCR actions handling • Simulation results • Conclusion Presented by Ki (2004-02-04)

3. Introduction • True VoD systems use dedicated channel for each user • Respond to users quickly • Server bandwidth runs out quickly • Expensive and not scalable Presented by Ki (2004-02-04)

4. Introduction • Near VoD systems let multiple users share video streams • Scheduled multicast (Close-loop) • Transmission schedule adapt to users arrival pattern • Periodic broadcast (Open-loop) • Transmission schedule is fixed regardless of users arrival pattern • This paper proposes a novel architecture of a periodic broadcast system that guarantee to support VCR actions Presented by Ki (2004-02-04)

5. Conditions for continuous VCR • VCR functions can be classified into continuous and discontinuous functions • Continuous function • Play Forward/Play Backward • Fast Forward/Fast Backward • Slow Forward/Slow Backward • Pause • Discontinuous • Jump Forward/Jump Backward Presented by Ki (2004-02-04)

6. Channel 3 …… Channel 4 Channel K-2 Channel 5 Channel K-1 Conditions for continuous VCR d Channel 0 b Channel 1 Channel 2 Presented by Ki (2004-02-04)

7. Conditions for continuous VCR • Define • ∆(k0, k) be the distance (in second) from play point k0 to a future frame k at a normal play rate γ • c(k) be the time remaining until frame k is consumed • Then, • Consumption time of frame k ≥ time taken to consume all frames between k0 and k Presented by Ki (2004-02-04)

8. Conditions for continuous VCR • If B is a set of frames currently in buffer, continuous VCR functions can be provided if where b(k) is the next broadcast time of k • Minimal client buffer space required for a client to provide continuous VCR functions consistently is 2nm • must be in buffer before c(k) • Worst case: Presented by Ki (2004-02-04)

9. VCR-oriented periodic broadcasting (VPB) • VPB uses K/n channels each with bandwidth nb • Si is broadcast over channel Presented by Ki (2004-02-04)

10. VCR-oriented periodic broadcasting (VPB) • In VPB, the next broadcast time, b(k)≤ d • So if , continuous VCR functions can be provided • Frames with distance > nd do not have to be buffered as they can be obtained by next broadcast before consumption • If n = 3 and the current play point k0 is in Si, target segments containing required future frames are Si, Si+1, Si+2, Si+3 Presented by Ki (2004-02-04)

11. Reception Schedule • When S1 is being broadcast, S4, S7, …, SK/3-2 are also being broadcast • The following show the required frames to be stored when the channels are transmitting the target segments Presented by Ki (2004-02-04)

12. Reception Schedule • Since only the frames within the distance nd are considered, the total buffer requirement for forward and backward buffer is 2nm • Receive and store the currently broadcasting frame, kt, into buffer if • Continuous VCR actions are guaranteed Presented by Ki (2004-02-04)

13. Reception Schedule Presented by Ki (2004-02-04)

14. Discontinuous VCR Actions Handling • Discontinuous actions render the buffered content useless • Jump to the requested destination immediately maybe impossible due to buffer restrictions and the service latency in periodic broadcast • VPB provides VCR action guarantee as when the service start, except for backward action Presented by Ki (2004-02-04)

15. Discontinuous VCR Actions Handling • For (a), as all essential frames are in buffer, the action is allowed • For (b), the action is allowed if the current broadcast point satisfy • For (c), destination shift introduced • Maximum destination shift is nd/2 while the average is nd/4 Presented by Ki (2004-02-04)

16. Simulation Results • Parameters • Mean duration of cont. action = 10s • Mean jumping distance = 60s • Fast Forward/Backward rate, n = 3 • Segment length = 60s • No. of Segments = 32 • Normal playback bitrate, γ= 30fps Presented by Ki (2004-02-04)

17. Simulation Results Presented by Ki (2004-02-04)

18. proportion of not shifted actions Simulation Results • Proportion of shifted destinations increases with mean jump distance • The average shift distance increases with the mean jump distance • Long jump actions are probably not serviced by the buffered data Presented by Ki (2004-02-04)

19. Conclusion • This paper • analyzes the necessary conditions to provide VCR functions • proposes a VCR-oriented broadcasting scheme (VPB) that guarantee to support all continuous actions consistently and discontinuous actions with destination shift • VPB utilizes minimal client buffer requirement • VPB clients bandwidth increases with n Presented by Ki (2004-02-04)

20. Final Thoughts • VPB is a scheme that support VCR actions with the trade off of increased client bandwidth • It requires frame level synchronization, which may not be possible • Comparisons with other schemes should be provided Presented by Ki (2004-02-04)