1. The Split and Merge Protocol for Interactive Video-on-Demand Wanjiun Liao and Victor O.K. Li IEEE Multimedia

2. Outline Introduction Introduction The Split and Merge (SAM) protocol The Split and Merge (SAM) protocol Illustration of the VCR operation Illustration of the VCR operation Results Results Conclusions Conclusions

3. Introduction True-Vod True-Vod Assign a dedicated video stream to customer Assign a dedicated video stream to customer Too Expensive (each stream requires high- speed data transport) Too Expensive (each stream requires high- speed data transport) Near-Vod Near-Vod Batching Batching Staggered Broadcast Staggered Broadcast Piggybacking Broadcast Piggybacking Broadcast

4. Previous Works P.S. Yu, J.L. Wolf, and H. Shachnai P.S. Yu, J.L. Wolf, and H. Shachnai Based on staggered broadcast Based on staggered broadcast developed the look-ahead scheduling with set-aside buffer protocol developed the look-ahead scheduling with set-aside buffer protocol only supports the interactive operation of pause and resume only supports the interactive operation of pause and resume V.O.K. Li et al. V.O.K. Li et al. Based on staggered broadcast Based on staggered broadcast creates a new stream to handle user interactions for each interactive user creates a new stream to handle user interactions for each interactive user work only if very few users issue interactive operations work only if very few users issue interactive operations L. Golubchik, J.C.S. Lui, and R.R. Muntz L. Golubchik, J.C.S. Lui, and R.R. Muntz Based on Piggybacking Based on Piggybacking This involved changing the display rates of user requests to batch the nearby streams This involved changing the display rates of user requests to batch the nearby streams

5. Split and Merge (SAM) 1. SAM starts by serving customers in a batch 2. When a user in a batch initiates a user interaction, the protocol splits off the interactive user from the original batch and temporarily assigns that user to a new video stream 3. With a dedicated video stream, the user can perform any interactions desired 4. As soon as the user inter-action terminates, the system merges this user back to the nearest ongoing video stream

6. Split and Merge (SAM) Service streams (S streams) Service streams (S streams) serve users during normal playback serve users during normal playback Typically a multicast stream, an S stream serves multiple users simultaneously Typically a multicast stream, an S stream serves multiple users simultaneously Interaction streams (I streams) Interaction streams (I streams) satisfy some user requests for VCR-like interactions satisfy some user requests for VCR-like interactions one I stream for one user one I stream for one user

7. Flowchart of SAM protocol ’ s operation

8. Split and Merge (SAM) Split and Merge operations Split and Merge operations No Streams No Streams S streams : Block a user request S streams : Block a user request I streams : Normal Play until the resource becomes available I streams : Normal Play until the resource becomes available An adaptive protocol An adaptive protocol Synchronization (synch) buffer Synchronization (synch) buffer To create a virtual stream To create a virtual stream

9. two segment time delay Real stream Virtual stream

10. VCR operation Jump-forward and jump-backward Jump-forward and jump-backward Fast-forward and rewind Fast-forward and rewind Pause and resume Pause and resume

11. Jump-forward and jump-backward

13. Fast-forward and rewind

15. Pause and resume

18. Variations of the basic scheme No initial batching delay No initial batching delay Adjustable batching intervals Adjustable batching intervals A variation of the basic batching idea A variation of the basic batching idea One synch buffer for multiple virtual streams One synch buffer for multiple virtual streams A pricing mechanism for user interactivity A pricing mechanism for user interactivity

19. Result 1 Blocking probability for the batching and nonbatching cases Average interaction delay as a function of arrival rates

20. Result 2 Blocking probability as a function of synch buffer allowed. Average interaction delay as a function of synch buffer allowed

21. Result 3 Blocking probability as a function of number of I streams Average interaction delay as a function of the number of I streams

22. Conclusions Our proposed protocol lets multiple users share the same video stream, dramatically increasing the capacity of the system and greatly reducing the costs per user. Our proposed protocol lets multiple users share the same video stream, dramatically increasing the capacity of the system and greatly reducing the costs per user. At the same time, the price batching delay, interaction delay, and so forth — remains tolerable. At the same time, the price batching delay, interaction delay, and so forth — remains tolerable.