nus.soc.cs5248 Ooi Wei Tsang

Recent Papers

from conferences

nus.soc.cs5248 Ooi Wei Tsang

Sessions

•Session 1: Movies and Music•Session 2: Peer-to-Peer

Streaming•Session 3: Power-Friendly

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Movies and Music

Session 1

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Characterizing DVD

Wu-Chi Feng et. al.Packet Video 2003

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Motivations

• Lots of DVD videos available• How are they encoded?• What is the implications to our

research?

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DVD data

•107 video streams•140 hours•80 DVDs

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Bit-rates

• Maximum DVD bit rates 10 Mbps• Found on DVD 3.3 – 7.8 Mbps

• VBR• Quantization values change over time

(only Spy Kids is CBR)

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GOPs and Sequences

• Each GOP was encoded into a different sequence

• GOP sizes: around 12 frames

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Sequence

sequence header:• width• height• frame rate• bit rate• :

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GOP: Group of Picture

gop header:• time• :

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Picture

pic header:• number• type (I,P,B)• :

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Frame Patterns

• Most videos have varying• Number of frames within a GOP • Frame patterns

(ID4 has 134 unique GOP

patterns)

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Frame Pattern

• Scene Change Detection used extensively

• IPPPPPPP quite common!

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Implication to Research

• Cannot assume fixed frame pattern

• Cannot always drop B frames

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Network Musical Performances

UC BerkeleyNOSSDAV 2001

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Goal

• Show that networked musical performances (NMP) can be done

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Observation

• Stanford – Berkeley (40 miles)• RTT ~4 ms• 0.72 meters

• Berkeley – Caltech (375 miles)• RTT ~28 ms• 4.88 meters

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Observation

• Musical instruments have long production latency

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Observation

• Don’t send audio, send command

• Keeps “states” of the current music performance

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Example

• NoteOn(channel, note, velocity)• NoteOff(channel, note)

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Packet Loss Recovery

• Lost/Late NoteOn • skipped

• Lost/Late NoteOff• executed

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Packet Loss Recovery

• Guard packets

• Recovery journals

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Bandwidth

• 20 MIDI command per seconds• 640 bps

• With recovery journals• ~7 kbps

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Experience

• Lost/Late NoteOn/NoteOff

• But musician can adjust and play fluidly

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Peer-to-Peer

Session 2

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P2Cast

Yang Guo et. al. WWW 2003

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Patching

Time

Client Request

mcast

unicast

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Patching

Time

Client Request

Patching Window: W

mcast

mcast

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Problem with VOD

• IP Multicast usually assumed• Patching still requires unicast

connections

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P2Cast

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New Session

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Existing Session + Patch

?

?

Fat Pipe First

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Patch Server Selection

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Patching Stream

patching stream

base stream

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Tree Example

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Failure Recovery

X

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Failure Recovery

• What if• Patch server failed?

• Base server failed?

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PROMISE

Mohamed Hafeeda et. al.

ACM MM 2003

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Problem

• P2P with streaming• One peer may not have enough

bandwidth• Need to aggregate multiple

peers

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Architecture

B/2B/4B/4

CollectCast

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CollectCast

• Select sending peers• Monitor network• Assign streaming rates and data

segments• Decide when to change peers

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PROMISE Operations

I want to watch

LOTR:T2T

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PROMISE Operations

These are the

candidates..

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PROMISE Operations

Max expected goodnessSubject to rate constraints

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PROMISE Operations

Here are your peers!

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PROMISE Operations

Send these..

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PROMISE OperationsShould

I switch

?

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PALS

Reza Rejaie et. al.NOSSDAV 2003

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Problem

• P2P with streaming• One peer may not have enough

bandwidth• Need to aggregate multiple

peers•Using layered coding•With congestion control

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Sliding Window

playout time window

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Packet Assignment

playout timeS1 S2

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Sending Mechanism

• Request packets in priority order• Sender must send in order• Next request overwrites previous

one

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Power-Friendly

Session 3

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GRACE-OS

Wanghong YuanSOSP 2003

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Motivation

• Mobile devices run on battery• How to save battery?

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Dynamic Voltage Scaling

•Example: AMD Athlon 4 PowerOn {300, 500, 600, 700, 800, 1000}MHz

• Energy V2

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CPU Scheduler

•When to execute a task•How long to execute it•How fast to execute it

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CPU Reservation

“I need C units of time, out of every T units.”

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Probability Distribution

cycles

Cum. Prob.

500

0.8

80% ofthe time,this taskrequires 500 cycle.

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CPU Requirements

• “I need C units of time, out of every T units.”

• CPU only needs to run at

“With 80% success rate, C is 500 cycle”

i i

i

T

C

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Speed Schedulesp

eed

time

If task can finish early, we save energyby not running it at higher speed

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Finding Speed Schedule

• Let task execute at speed vx

during cycle x• execution time: 1/vx

• power: vx2

• average power: (1-F(x))vx2

nus.soc.cs5248 Ooi Wei Tsang

Optimize This

• Minimize:

• Subjected to:

C

xxvxF

0

2))(1(

i

C

x x

TiCiC

v1

1

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Implementation

• Linux Kernel• AMD Athlon 4•716 lines of code

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Findings

• Probability distribution is quite stable

• Able to meet deadlines with bounded miss ratio

• Save energy by 7 – 72%

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Proxy Assisted Streaming

Prashant Shenoy et. al.MMCN 2003

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Motivation

• Power-aware streaming to mobile device• save energy in decoding frames• save energy in receiving packets

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Architecture

server/proxy client

Here’s my energy budget for decoding +

network reception and max resolution

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Architecture

server/proxy client

OK, what should I send?

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Information Needed

• Map stream properties to energy requirement

• Need to know decoding time of a frame

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Frame Decoding Time

Frame Size (bits)

Time (s)

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Transcoding

• If current stream would exceed client decoding energy budget

• Need to transcode by reducing quality

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Transcode to what?

E = estimated energy neededwhile E > energy budget reduce quality by ε E = estimate energy needed

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Transcoded Streams

server/proxy client

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Reducing NIC Energy

• NIC has two modes : active/sleep

• Client can activate NIC only when packets are expected.

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Burst Transmission

I will start transmitting at

10:12:54.86 pm

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EvaluationsDecoding Time

Frame Number

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Evaluations

• NIC Idle Uptime: 2 – 20%