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An Ef fi cient Implementation of Interactive Video-on-Demand. Steven Carter and Darrell Long University of California, Santa Cruz Jehan-Fran çois Pâris University of Houston. Why Video-on-Demand?. Increased customer convenience Few people enjoy returning video tapes

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An ef cient implementation of interactive video on demand l.jpg

An Efficient Implementation of Interactive Video-on-Demand

Steven Carter and Darrell Long

University of California, Santa Cruz

Jehan-François Pâris

University of Houston


Why video on demand l.jpg
Why Video-on-Demand?

  • Increased customer convenience

    • Few people enjoy returning video tapes

      • Even fewer people enjoy paying late fees

  • Improved selection of videos

    • Current pay-per-view provides only a small selection of popular videos

  • Savings in time and resources

    • It takes time and fuel to drive to the video rental store


Why now l.jpg
Why Now?

  • Technology becoming available

    • Processors are inexpensive

    • Storage is nearly free ($200 for 40GB)

    • Fast networking is seeing wide deployment

  • Consider the success of Tivo

    • Records live television using MPEG to disk

    • Provides interactive access to recorded programs


Why interactive l.jpg
Why Interactive?

  • It’s hard! It’s more expensive!

    • … but it’s what people expect

  • They won’t give up functionality they have come to expect

    • They’d like to pause to make microwave popcorn

    • They’d like to rewind to see the play again

    • They’d like to be able to fast forward past the boring parts


Related research l.jpg
Related Research

  • Conventional video-on-demand (VoD)

    • Requires one stream per client

  • Patching

    • An independently developed version of stream tapping

  • Batching

    • Group the requests of several clients together

  • Various near video-on-demand (NVoD) schemes


Key observation l.jpg
Key Observation

  • For videos of non-trivial length, several clients will be viewing portions of that video

    • One client watching a 120 minute video and a second client begins watching the same video 10 minutes later

  • The server needs only send data for the non-overlapping portion

    • The potential for savings is enormous


Assumptions l.jpg
Assumptions

  • A set-top-box with:

    • A fast network connection

    • A few gigabytes of local storage

    • A modest processor

  • Keep in mind that set top boxes with these features already exist


Our solution l.jpg
Our Solution

  • Stream Tapping uses multicast to tap in existing video streams

  • Server load is the primary difficult in making VOD a reality

    • Stream Tapping reduces server load by allowing clients to tap into video streams created for other clients

    • Cost per client is dramatically reduced

  • Client waiting time is also reduced


Stream types l.jpg
Stream Types

c

c

C

Partial tap

b

b

Full tap

Stream

B

Complete stream

A

0

2

3

4

Time (since start of complete stream A)


Complete streams l.jpg
Complete Streams

  • Start at a particular position in a video and transmit the remainder of the video

    • For non-interactive Stream Tapping, the starting position is the beginning of the video

  • Used primarily by the first client in a group to view the video


Stream types11 l.jpg
Stream Types

c

c

C

Partial tap

b

b

Full tap

Stream

B

Complete stream

A

0

2

3

4

Time (since start of complete stream A)


Full tap streams l.jpg
Full Tap Streams

  • Can be used if the delay () is less than the buffer size ()

  • The full tap stream transmits the video from time 0 to 

  • The complete stream is tapped and written to the buffer while the full tap stream is played


Stream types13 l.jpg
Stream Types

c

c

C

Partial tap

b

b

Full tap

Stream

B

Complete stream

A

0

2

3

4

Time (since start of complete stream A)


Partial tap streams l.jpg
Partial Tap Streams

  • Can be used when a complete stream is available but   

    • Note that given current technology,  will be very large

  • The client will tap the complete stream for  units while simultaneously viewing the first  from a partial tap stream

  • Subsequently, partial tap streams of length    are used for the client to catch up to the complete stream


Stream types15 l.jpg
Stream Types

c

c

C

Partial tap

b

b

Full tap

Stream

B

Complete stream

A

0

2

3

4

Time (since start of complete stream A)


Tapping options l.jpg
Tapping Options

  • Extra Tapping

    • Allows the client to tap data from any active video stream active, not just the complete stream of the video group

    • Decreases server load by decreasing the length of full tap streams

  • Stream Stacking

    • If the server has streams available, the client can combine them to receive data at rate higher than the nominal rate

    • Allows the server to service stream more quickly, which allows new streams to be scheduled


Interactive stream tapping l.jpg
Interactive Stream Tapping

  • When an interaction begins, Stream Tapping deallocates resources associated with a client

    • If the client was the only one using a stream, then the stream is terminated

  • Stream Tapping determines the resources needed for an interaction, and allocates an interaction stream

    • Note: for rewind, the client’s buffer can be used

  • When the interaction is complete, the client is merged into a video group (tapping existing streams if available)


Contingency streams l.jpg
Contingency Streams

  • These are streams that are held in reserve for interaction

  • The pool of these streams can be managed using high and low watermarks for hysteresis

  • Having such a reserve of streams is essential to avoid blocking


Simulation model l.jpg
Simulation Model

  • Stream Tapping is too complex to model analytically, so we used discrete event simulation

  • The length of the videos was derived from empirical data and a gaussian with mean 102 minutes provided the best fit

  • The popularity of videos was modeled using a Zipf-like distribution, which is the distribution used in most VoD studies








Conclusions l.jpg
Conclusions

  • Stream Tapping has been shown to work well in the interactive environment

  • We have shown that VCR-like controls are possible

    • Previous work has ignored them or only provided course-grained control

  • The use of storage in the STB is an enabling technology



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