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Transmitting Scalable Video over
a DiffServ network
EE368C
Project Presentation
Sangeun Han, Athina Markopoulou
3/6/01
Sangeun Han, Athina Markopoulou
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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.
Sangeun Han, Athina Markopoulou
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Specifics
• What type of scalability? H.263+, SNR
EL
EI
EP
EP
EP
BL
I
P
P
P
• Which DiffServ class? AF (priority dropping)
buffer
packet
scheduling
conditioning management
EF
classification
AF11
high strict priority
AF1
w2
AF2
w3
AF3
w4
AF4
w5
BE
w6
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Simulation scenario
Main stream: Foreman (10fps)
136Kbps, BL+EL, 2min
10-20 Interfering Streams
BL+EL~=136Kbps
random parts of 6 different streams
H.263+
Encoder
+
Layering
RTP
Packet.
for H.263
(*)
Single AF queue,
2 levels, 100KB
1.5Mbps
Marker
Depackt.
Loss
info
(*) Mode A: at frame level,
Total header= IP(20)+UDP(8)+RTP(12)+H.263(4)=44B
Decoding+
[Error
Conceal.] (**)
Original
Stream
(**) Freezing previous frame
Sangeun Han, Athina Markopoulou
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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?
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MUX gain
Layered+PD
Nonlayered
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Graceful degradation with loss
FGS
NL, no loss
Layered+loss
+ data loss
Non Layered + loss
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Short Term Congestion
• The source may react to congestion by adapting its
transmission rate...
Rate
Congestion
EL
BL
Reaction
with no
delay D=0
time
R
time
D
D
Reaction
with Delay
D>0
time
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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]
Sangeun Han, Athina Markopoulou
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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]
Sangeun Han, Athina Markopoulou
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Priority dropping vs Feedback
• Feedback
•
•
•
•
is limited by delay
saves network resources
requires coordination
Priority Dropping
– is like reaction in D=0, by appropriate rate decrease
– may handle non adaptive sources
Rate
EL
Congestion
R(t
)
BL
time
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Configuration of AF queue
BL - low drop precedence
EL - high drop precedence
Drop
prob
1
• Choices:
0
High drop Low drop
L_min
L_max
H_min,max
Buffer occupancy
– 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
Sangeun Han, Athina Markopoulou
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RED worse than DropTail
For all loads….
and
…for all thresholds
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Threshold for EL(HP)
• By assigning the buffer
thresholds
– we control the Queue
Occupancy for BL, EL
Threshold_HDP = 56
Threshold_HDP = 16
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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]
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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
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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
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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
Feedback
BL2
BL1
PD
Rate
loss
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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
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