1Sangeun Han, Athina Markopoulou

Transmitting Scalable Video over a DiffServ network

EE368C Project Presentation

Sangeun Han, Athina Markopoulou3/6/01

2Sangeun Han, Athina Markopoulou

Project Proposal• Problem:

– Video transmission over the heterogeneous Internet • Facts:

– Scalability: different parts of a video stream contribute unequally to the quality.

– DiffServ Networks can provide service differentiation, based on the marking of packets.

• Proposal– Limit the effect of loss when it happens. Prioritize

information according to importance and drop packets accordingly.

3Sangeun Han, Athina Markopoulou

Specifics• What type of scalability? H.263+, SNR

• Which DiffServ class? AF (priority dropping)

EF

AF1

AF2

AF3

AF4

BE

w2

w3

w4

w5

w6

buf fe rm a nagem ent

packe tsc heduling

high s t r ic t p r io rity

conditioning

classification

AF11

I P P P

EI EP EP EPEL

BL

4Sangeun Han, Athina Markopoulou

Simulation scenario

(*) Mode A: at frame level,Total header= IP(20)+UDP(8)+RTP(12)+H.263(4)=44B

(**) Freezing previous frame

H.263+Encoder

+Layering

RTPPacket.

for H.263(*)

Decoding+[Error

Conceal.] (**)Depackt.Marker

Single AF queue,2 levels, 100KB

Main stream: Foreman (10fps) 136Kbps, BL+EL, 2min

10-20 Interfering StreamsBL+EL~=136Kbpsrandom parts of 6 different streams

1.5Mbps

Loss info

Original Stream

5Sangeun Han, Athina Markopoulou

Objective of the Project• Show the benefit from using Priority Dropping

for Scalable Video– MUX gain– Graceful Quality Degradation – Handle short term congestion

• Configuration – AF queue:

• buffer management, thresholds, other parameters– Layering parameters

• base layer, temporal dependence• Recommendation

– To Feedback or to Drop?

6Sangeun Han, Athina Markopoulou

MUX gain

Nonlayered

Layered+PD

7Sangeun Han, Athina Markopoulou

Graceful degradation with loss

Layered+loss

Non Layered + loss

NL, no lossFGS

+ data loss

8Sangeun Han, Athina Markopoulou

Short Term Congestion• The source may react to congestion by adapting its transmission

rate...

Congestion

time

Rate

BLEL

D Dtime

time

Reaction with no delay D=0

Reaction with Delay D>0

R

9Sangeun Han, Athina Markopoulou

Reaction time vs.congestion duration

• Simple example: – 10 streams + 5 more in [55sec,65sec]– 10 streams react by dropping their EL in [55+D, 65+D]

10Sangeun Han, Athina Markopoulou

Heavier congestion

• Heavy + non adaptive interfering traffic: – 10 streams + 10 more in [55sec,65sec]– 10 streams react by dropping their EL in [55+D, 65+D]

11Sangeun Han, Athina Markopoulou

Priority dropping vs Feedback

• Priority Dropping – is like reaction in D=0, by appropriate rate decrease– may handle non adaptive sources

Congestion

time

Rate

BLEL

R(t)

• Feedback • is limited by delay• saves network resources• requires coordination

12Sangeun Han, Athina Markopoulou

Configuration of AF queue

• Choices:– Thresholds for the different priorities– Buffer management: RED or DropTail?

• Observations:– Not sensitive to choice of thresholds– RED inappropriate: do not use Avg Qsize, set Lmin=Lmax– Differentiation: (I) different thresholds (II) Occupancy

Low dropDropprob High drop

Buffer occupancy

1

0

BL - low drop precedence EL - high drop precedence

L_min L_max H_min,max

13Sangeun Han, Athina Markopoulou

RED worse than DropTailFor all loads….

…for all thresholds

and

14Sangeun Han, Athina Markopoulou

Threshold for EL(HP)

• By assigning the buffer thresholds – we control the Queue

Occupancy for BL, EL

Threshold_HDP = 56 Threshold_HDP = 16

15Sangeun Han, Athina Markopoulou

Threshold for EL(LP)

• …this way we distribute the loss among BL and EL

• ….and thus the quality

• Insensitive to:• RED, DropTail• BL choice• [more sensitive to load]

16Sangeun Han, Athina Markopoulou

Effect of BL (I): on quality degradation

QP(BL)=12, 1:1, (BL=64kbps:EL=74kbps)QP(BL)=15, 1:2, (BL=50kbps:EL=86kbps)QP(BL)=30, 1:4, (BL=27kbps:EL=110kbps)

Same target rate: BL+EL~=136kbps

17Sangeun Han, Athina Markopoulou

Effect of BL (II): on thresholds

QP(BL)=12, 1:1, (BL=64kbps:EL=74kbps)QP(BL)=15, 1:2, (BL=50kbps:EL=86kbps)QP(BL)=30, 1:4, (BL=27kbps:EL=110kbps)

Same target rate: BL+EL~=136kbps

18Sangeun Han, Athina Markopoulou

Transmission of Scalable Video

• Use feedback + adaptation at the source to match the transmission rate with the bottleneck bandwidth, to save network resources along the path

• Use Priority Dropping to handle short term congestion Quality

Rate

PD

loss

Feedback

BL1

BL2

19Sangeun Han, Athina Markopoulou

Future work• Improvements needed

– realistic feedback + adaptation– >2 layers– finish FGS

• New experiments needed– Delay aspect:

• Loss at the playback buffer • Entire streams having different delay requirements

– Multiple hops– Single wireless hop (802.11 + QoS)– Video + Data– Larger Bandwidths– Other types of scalability: FGS, Temporal, Spatial, DP