Christian Timmerer, Víctor H. Ortega, José M. González, and Alberto León, Measuring Quality of Experience for MPEG-21-based Cross-Layer Multimedia Content Adaptation, Proceedings of the 1st ACS/IEEE International Workshop on Wireless Internet Services (WISe'08), Doha, Qatar, April 1-4, 2008.

1. Measuring Quality of Experience for MPEG‐21‐based
Cross‐Layer Mul>media Content Adapta>on
Chris&an Timmerer
Klagenfurt University (UNIKLU)  Faculty of Technical Sciences (TEWI)
Department of Informa&on Technology (ITEC)  Mul&media Communica&on (MMC)
hBp://research.>mmerer.com  hBp://blog.>mmerer.com 
mailto:chris>an.>mmerer@itec.uni‐klu.ac.at
Co‐Authors: Chris>an Timmerer (University of Klagenfurt, Austria), Víctor H. Ortega (Tecsidel, Spain), José M.
González, and Alberto León (Telefonica, Spain)
Acknowledgment: This work is supported by the European Commission in the context of the ENTHRONE project
(IST‐1‐507637). Further informa>on is available at hBp://www.ist‐enthrone.org.

2. Outline
• Overview and Context
• Probing Quality of Service / Experience
• MPEG‐21 Overview (Digital Item Adapta>on)
• An Interoperable QoS Model for Video
Transmission Exploi>ng Cross‐Layer Interac>ons
• Conclusions
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 2

3. Overview and Context
Content Adapta&on
for Universal Access
Heterogeneous Networks,
Diverse Set of
Dynamic Condi&ons
Rich Mul&media Terminal Devices,
Content User Preferences
Growing mismatch
⇓
Need for scalable content, descrip&ons, nego&a&on, adapta&on
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 3

4. Overview and Context
Content Adapta&on
for Universal Access
... but, where‘s the
Heterogeneous Networks,
(end) user? Diverse Set of
Dynamic Condi&ons
Rich Mul&media Terminal Devices,
Content User Preferences
Growing mismatch
⇓
Need for scalable content, descrip&ons, nego&a&on, adapta&on
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 4

5. Overview and Context (cont‘d)
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 5

6. Overview and Context (cont‘d)
Cross‐Layer Style
End‐to‐End QoS Management + Interoperability
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 6

7. Probing Quality of Service / Experience
Audio
• ETSI/ITU‐T‘s E‐model: quot;Psychological factors on the psychological
scale are addi>vequot;
• Factors: packet loss, delay, equipment impairment, packet loss
robustness factors (depends on codec)
Video
• Profiles/Levels with diff. resolu>ons, frames per second, bit rates,
etc.
• Peak Signal to Noise Ra>o (PSNR), Mean Opinion Square (MOS),
Video Quality Metric (VQM)
• Various models exist, e.g., perceptual impression of packet loss,
frame rate varia>on and sync. w/ audio
 need for interoperable solu&ons
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 7

8. The MPEG‐21 Mul>media Framework
MPEG‐21 Vision
• ... to enable transparent and augmented use of mul>media resources
across a wide range of networks, devices, user preferences, and
communi>es, notably for trading (of bits)
What ? – Digital Items (DIs)
• A Digital Item (DI) is a structured digital object with a standard
representa>on, iden>fica>on, and metadata within the MPEG‐21
framework
• Digital Items are “the content”
Who ? – Users
• A User is any en>ty that interacts in the MPEG‐21 environment or makes
use of a Digital Item
• Users will assume rights and responsibili>es according to their interac>on
with other Users
• All par>es that have a requirement within MPEG‐21 to interact are
categorized equally as Users
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 8

9. MPEG‐21 Organisa>on – Parts
Digital Adapta&on Processing Systems Misc
Rights Pt. 7: Digital Pt. 10: Digital Pt. 9: File Pt. 8: Reference
Management Item Adapta>on Item Processing Format Sosware
Pt. 11: Persistent
Amd.1: Add‘l Pt. 16: Binary
Amd.1: Convers.
Pt. 4: IPMP
Associa>on
C++ bindings Format
And Permissions
Components
Pt. 12: Test Bed
Pt. 18: Digital
Amd.2: Dynamic
Pt. 5: Rights
Item Streaming
and Distributed Pt. 14: Conform.
Expression Lang
Adapta>on
Pt. 15: Event
Pt. 6: Rights
Repor>ng
Data Dic>onary
Pt. 17: Fragment
Amd.1: DII
Idenfica>on
rela>onship types
Vision, Declara&on, and Iden&fica&on
Pt. 1: Vision, Technologies Pt. 2: Digital Item Pt. 3: Digital Item
and Strategy Declara>on Iden>fica>on
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 9

10. MPEG‐21 Digital Item Adapta>on
• Sa>sfy transmission, storage and consump>on constraints as well as QoS
management
• Enable transparent access to (distributed) advanced mul>media content
by shielding users from network and terminal installa>on issues
Relevant Tools (among other)
• Usage Environment Descrip>on (UED)
– network, terminal, user, natural
environment
• Universal Constraints Descrip>on (UCD)
– limita>on, op>miza>on
• Adapta>onQoS
– rela>onship between constraints (i.e., the UED/UCD), feasible adapta>on
opera>ons (e.g., transcoding, scaling, etc.) sa>sfying these constraints, and
associated u>li>es (i.e., quali>es / PSNR).
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 10

11. An Interoperable QoS Model for Video
Transmission Exploi>ng Cross‐Layer Interac>ons
• AVC test content: frame rate [6.25,25] fps; bit rate
[150,1500] kbps; packet loss [0,10] %
• Public survey (across EU) – boBom‐up approach
Impact of Packet Loss
• Bernoulli model => packet loss randomly distributed
over uniform probability density func>on (all packets
have same probability to be dropped)
• Real world: packet loss == bursts of random length
(1)
 calculate the quality in short intervals
(packet loss density distribu>on can be considered
uniform even if we are inside a burst)
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 11

12. An Interoperable QoS Model for Video
Transmission Exploi>ng Cross‐Layer Interac>ons
• AVC test content: frame rate [6.25,25] fps; bit rate
[150,1500] kbps; packet loss [0,10] %
• Public survey (across EU) – boBom‐up approach
Impact of Packet Loss
• Bernoulli model => packet loss randomly distributed
over uniform probability density func>on (all packets
have same probability to be dropped)
• Real world: packet loss == bursts of random length
(1)
 calculate the quality in short intervals
(packet loss density distribu>on can be considered
uniform even if we are inside a burst)
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 12

13. An Interoperable QoS Model for Video Transmission
Exploi>ng Cross‐Layer Interac>ons (cont’d)
Impact of Bandwidth
• Different bandwidth curves studied
 rela>onship between bit rate and the packet loss
(2)
Impact of Frame Rate
• Classifica>on according to temporal nature +
actual audio‐visual content: [1..7] (7 is the best)
 Extrapolated for VoD szenarion with high
temporal nature (3)
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 13

14. An Interoperable QoS Model for Video Transmission
Exploi>ng Cross‐Layer Interac>ons (cont’d)
Impact of Bandwidth
• Different bandwidth curves studied
 rela>onship between bit rate and the packet loss
(2)
Impact of Frame Rate
• Classifica>on according to temporal nature +
actual audio‐visual content: [1..7] (7 is the best)
 Extrapolated for VoD szenarion with high
temporal nature (3)
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 14

15. An Interoperable QoS Model for Video Transmission
Exploi>ng Cross‐Layer Interac>ons (cont’d)
Proposed Model
(4)
 add interoperability support
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 15

16. Adding MPEG‐21 Support Enabling
Interoperable Cross‐Layer Interac>ons
AdaptationQoS Stack Function for MOS (aqos.xml):
<!-- Stack Function for MOS calculation -->
• Describe func>onal dependencies of (4) <Module xsi:type=quot;StackFunctionTypequot;
iOPinRef=quot;MOSquot;>
<StackFunction>
– MPEG‐21 DIA Adapta>onQoS' stack <Argument xsi:type=quot;InternalIOPinRefTypequot;
iOPinRef=quot;F_FRAMERATEquot;/>
func>ons <Argument xsi:type=quot;InternalIOPinRefTypequot;
iOPinRef=quot;F_PACKETLOSSquot;/>
– Range of possible content frame rate and <!-- multiply -->
<Operation operator=quot;:SFO:18quot;/>
bit‐rate combina>ons  solu>on space </StackFunction>
</Module>
UCD maximizing the MOS (ucd_provider.xml):
<OptimizationConstraint optimize=quot;maximizequot;>
<Argument xsi:type=quot;ExternalIOPinRefTypequot;
• Usage environment: network condi>ons UED (ued.xml): iOPinRef=quot;aqos.xml#MOSquot;/>
</OptimizationConstraint>
(bandwidth, packet loss) <Network xsi:type=quot;NetworkTypequot;>
<NetworkCharacteristic
– MPEG‐21 DIA Usage Environment Descrip>on xsi:type=quot;NetworkConditionTypequot;>
<AvailableBandwidth average=quot;1500000quot;/>
<Error packetLossRate=quot;0.03quot;/>
</NetworkCharacteristic>
</Network>
• Constraints of the probe (pl, br, fps) + UCD for probe constraints (ucd_probe.xml):
<!-- packet loss <= 0.1 (10%) -->
objec>ve func>on, i.e., maximize the MOS <LimitConstraint>
<Argument xsi:type=quot;SemanticalRefTypequot;
semantics=quot;:AQoS:6.6.5.8quot;/>
– MPEG‐21 DIA Universal Constraints Descrip>on <Argument xsi:type=quot;ConstantDataTypequot;>
<Constant xsi:type=quot;FloatTypequot;>
<Value>0.1</Value>
</Constant>
</Argument>
<Operation operator=quot;:SFO:38quot;/>
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 16
</LimitConstraint>

17. Conclusions and Future Work
• QoS/QoE: guarantee the quality of mul>media traffic
experimented by the user
 translate network issues into user perceived quality
• New model for evalua>ng the quality of video streams
proposed – extracted from RTP traffic
• Interoperability across layers through MPEG‐21
• @TODO evalua>on in large‐scale pilots featuring inter‐
connected test‐beds across Europe  FP6‐IST‐
ENTHRONE
2008/04/03 Chris>an Timmerer ‐ UNIKLU ‐ WISe'08, Doha, Qatar 17