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Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Kyoungwoo Lee, Minyoung Kim, Nikil Dutt, and Nalini Venkatasubramanian
Error-Exploiting Video Encoder
to Extend Energy/QoS Tradeoffs
for Mobile Embedded Systems
Department of Computer Science
University of California at Irvine
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces DIPES '08 #2
Outline
Motivation
Our Solution
Experiments
Conclusion
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Energy Reduction is Essential
DIPES '08 #3
Mobile computing is popular
Wellness Science
Communication, Entertainment, & Education
Business
Battlefield
Resource-limited mobile devices!Fundamental problem is to achieve low power with high performance
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Mobile Video ApplicationsMobile video applications demand high energy
consumptionComplex video encoding/decoding algorithmsTransmitting huge volume of video data
DIPES '08 #4
Network
Mobile Video Applications
ME DCT Q EE
f4f3
f2f1
Essential to extend the tradeoff space of energy consumption and QoS
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Energy/QoS Video Encodings
Energy/QoS-aware video encodingVideo encoding parameters [Mopatra, IPDPS05]Motion estimation algorithm [Tourapis, VCIP00] Integrated power management [Mohapatra, ACM MM03]Global cross-layer adaption [Yuan, MMCN04]Transmission power and QoS [Eisenberg, IEEE Trans.
on CSVT 02]
No Error ResiliencePBPAIR (Probability-Based Power Aware Intra Refresh)
– error-resilient and energy-efficient [Kim, MCCR06]
Passive Error Exploitation
DIPES 08 #5
Our solution – Active Error Exploitation to reduce the energy consumption for video encoding
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Active Error Exploitation
Active Error Exploitation – Intentional Frame DroppingSkip the expensive video encoding algorithm
Energy savingDegrade the video quality
Inherent error-tolerance mitigates the impact of frame drops on video quality
DIPES 08 #6
f1
f4f3
f2
Network
Mobile Video Applications
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Frame Drop Types
FDT-1 affects the following components with respect to power, performance, and QoS in mobile video applicationsThis work studies FDT-1, and future work includes FDT-2 and
FDT-3
DIPES 08 #7
Error-prone Networks
Mobile Video Application
Enc
CPU
Tx
WNI
Dec
CPU
Rx
WNIFDT-1FDT-1 FDT-2FDT-2 FDT-3FDT-3•FDT: Frame Drop Type
•Enc: Encoding, Dec: Decoding•WNI: Wireless Network Interface
Packet Loss
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Frame Losses due to Packet Losses
DIPES '08 #8
Error-Induced Video Data
f1
f4f3
f2
f4 is lost
Error-ProneNetwork
f1
f3f2
Inherent Error-Tolerance of Video DataError-Resilient/Error-Concealment Techniques
Mobile Video Applications
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Inherent Error-Tolerance of Video Data
Error-Tolerance of Video DataSpatial and temporal correlation
among consecutive video framesLossy video encoding
(e.g.) High Quantization Scale
Energy Reduction and Error-ToleranceError-tolerance can be used
for energy reduction(e.g.) partial ME vs. Full ME
One frame loss may not be noticed by users(e.g.) One frame loss out of 30 frames
per secondDIPES '08 #9
f1
f4f3
f2
Mobile Video Encoding
ME DCT Q EE
ME – Motion EstimationDCT – Discrete Cosine Transform
Q – QuantizationEE – Entropy Encoding
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Error-Resilient Techniques
Insert Intra-frames (I-frames) periodically
DIPES '08 #10
Error-Induced Video Data
f1
f4f3f2
Error-ProneNetwork f4 is lost
f1f3f2
GOP-K (Group-Of-Picture with K)(e.g.) GOP-3 inserts I-frame every 3 P-frames
Error-resilient GOP [Yang, JVCIP07]
Intra refresh video encoding techniquesAIR (Adaptive Intra Refreshing) [Worral, ICASSP01]PGOP (Progressive GOP) [Cheng, PCS04]PBPAIR (Probability-Based Power Aware Intra
Refresh) [Kim, MCCR06](e.g.) PBPAIR encodes video data resilient against 25% frame
loss rate (1 frame out of 4 frames)
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Energy Efficiency
Energy-efficient error-resilient video encodings (e.g.) PBPAIR or Probability-Based Power Aware Intra
Refresh [Kim, MCCR06] It may improve not only the video quality but also energy
consumption
DIPES 08 #11
Error-Induced Video Data
f1
f4f3
f2
Error-ProneNetwork f4 is lost
f1
f3f2
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces DIPES '08 #12
Outline
Motivation
Our SolutionError-Exploiting Video EncodingEE-PBPAIR
Experiments
Conclusion
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Our Proposal
Error-exploiting video encoder Intentional frame dropping + error-resilient video
encoding Extends the tradeoff space for energy consumption /
QoS
DIPES 08 #13
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Error-Resilient Video Encoder
DIPES 08 #14
Error-ResilientEncoder
Error-Resilient Video Encoder
OriginalVideoData
Error-Resilient
VideoData
Parameters
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Error-Exploiting Video Encoder
DIPES 08 #15
ErrorController
Error-ResilientEncoder
Error-Exploiting Video Encoder
OriginalVideoData
Error-InjectedVideoData
Error-AwareVideoData
Constraints Parameters& Feedback
Error-Injecting Unit Error-Canceling Unit
Reduce Energy
ConsumptionIncur Energy
Overhead
Combined approach may consume less energy
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Intentional Frame Dropping and PBPAIR
Energy EfficiencyFrame Dropping
(e.g.) f2 is dropped
PBPAIR
DIPES 08 #16
Quality ManagementError-Resilience
(e.g.) EE-PBPAIR encodes video data resilient against f2 and f4
Error-Tolerance
Error-Induced Video Data
f1
f4f3
f4 is lost
Error-ProneNetwork
f1f3
IntentionalFrame Dropping
PBPAIR
EE-PBPAIR
Error-Injecting Unit Error-Canceling Unit
f2 is dropped
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
EIR – Error Injection Rate
EIR adjusts the rate of intentional frame droppingEIR is Frame Drop Rate at Error-Injecting UnitEIR is translated for PBPAIR (considering it as PLR)Feedback-based quality adjustment
High EIR increases energy saving but degrades video quality
DIPES 08 #17
Frame Dropping PBPAIR
EE-PBPAIROriginal
VideoData
Error-AwareVideoData
ParametersQualityConstraintand QualityFeedback
Error-Injecting Unit Error-Canceling Unit
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces DIPES '08 #18
Outline
Motivation
Our Solution
Experiments
Conclusion
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
End-to-End Experimental Framework
End-to-End Experimental FrameworkMobile video applications such as video conferencing consist of
mobile encoding, wireless(and wired) networks, and mobile decoding
They affect each other in terms of energy consumption and QoS
System Prototype and NS2 SimulatorSystem Prototype
Runs video encoding and decoding on system prototype emulating mobile devices, and returns video quality in PSNR
Estimates the energy consumption of a processor (CPU power)
NS2 [http://www.isi.edu/nsnam/ns/]Network SimulatorEstimates the energy consumption of WNI (transmission power)
DIPES 08 #19
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Mobile Video Decoding
Experimental Setup
DIPES 08 #20
EncoderEncoder TransmitTransmit DecoderDecoderReceiveReceiveNetwork
NS2System Prototype
System Prototype
Mobile Video Encoding
CPU energy for encodingvideo quality (frame drop)
WNI energy for transmitWNI energy for receive
CPU energy for decodingvideo quality (packet loss)
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Evaluation
Video EncodingGOP-K (Group-Of-Picture with K)PBPAIR (Probability-Based Power Aware Intra Refresh)EE-PBPAIR (Error-Exploiting PBPAIR)
Energy ConsumptionEnc EC (Energy Consumption for Encoding) + Tx EC
(Energy Consumption for Transmission)Rx EC (Energy Consumption for Receiving) + Dec EC
(Energy Consumption for Decoding)
Video QualityVideo Quality at encoder after intentional frame droppingVideo Quality at decoder after packet losses in networks
DIPES 08 #21
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Experimental Results
Energy Reduction from Active Error ExploitationExtended Energy/QoS Tradeoff
DIPES 08 #22
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Energy Saving
DIPES '08 #23
EC = Energy ConsumptionEnc EC = EC for EncodingTx EC = EC for TransmissionDec EC = EC for DecodingRx EC = EC for Receiving
•PSNR: Peak Signal to Noise Ratio
PLR = 10% and EIR = 10%Energy saving occurs at every component in a path from
encoding to decoding in mobile video applications
Mobile Video Decoding
EncoderEncoder TransmitTransmit DecoderDecoderReceiveReceiveNetwork
Mobile Video Encoding
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Experimental Results
Energy Reduction from Active Error ExploitationExtended Energy/QoS Tradeoff
DIPES 08 #24
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Extended Tradeoff Space
DIPES '08 #25
PLR = 5% and EIR = 0% to 50%
EE-PBPAIR extends interesting tradeoff spaces
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Energy Reduction at QoS Cost
DIPES '08 #26
At 10% cost of video quality, EE-PBPAIR can save the energy consumption of Enc and Tx by up to 49%
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces DIPES '08 #27
Outline
Motivation
Our Solution
Experiments
Conclusion
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Conclusion
Intentional Frame Drop is one way to exploit errors actively
Propose an error-aware video encoding (EE-PBPAIR) Intentional frame dropping and the nature of energy-efficiency
of PBPAIR reduces the energy consumption for video encoding
Present a knob (EIR) to adjust the amount of errors considering the QoS feedback
Maintain the video quality using error-resilience of PBPAIR
Future Work Intelligent Frame Dropping Techniques Extend Active Error Exploitation to the system level with error-
aware architecture and network protocols in distributed embedded systems
DIPES 08 #28
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Thanks!
Any Questions?
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Backup Slides
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Intentional Frame Drop and Packet Loss
DIPES '08 #31
Error-prone Networks
Packet Loss
Intentional frame drop
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
EE-PBPAIR
DIPES '08 #32
Error-prone Networks
Packet Loss
Intentional frame
dropError-Exploiting Video Encoder
Error-ResilientEncoder
(e.g., PBPAIR)
Error-Controller(e.g., frame dropping)Error-Controller
(e.g., frame dropping)
OriginalVideo
Error-Resilient
Video
Error-AwareVideo
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Error Controller
DIPES '08 #33
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Error-Concealment
Error-Concealment Techniques Interpolate the lost frame using near framesSubstitute the near frame for the lost one
(e.g.) f2 is copied for f3 (the lost one) in displaying frames
DIPES '08 #34
Error-Induced Video Data
f1
f4f3
f2
Error-ProneNetwork f4 is lost
f1
f3f2
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
35
GOP (Group of Picture)
Standard H.263 Video Encoder with varying IP-ratio
Higher IP-ratio generates more compressed video output, which consumes more energy
Encoder
Static Constraint of Compression RateGOP
Standard video encoding, which is unaware of energyconsumption and error-resiliency
IP-ratio(KNOB)
Intra Frame
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
36
PBPAIR
Proactively estimate the probability of the correctness, and adapt the intra_th (KNOB) based on the current network PLR (Packet Loss Rate)
Encoder
PLR from Network ChannelPBPAIR
Error-Resilient Encoding, which can satisfy a given PSNR,and reduce the energy consumption for encoding
Intra_Th(KNOB)
Intra MB
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
37
EE-PBPAIR
EE-PBPAIR introduces another KNOB (intentional EIR) other than Intra_Th, and can further save the energy consumption
Encoder
PLR from Network ChannelEE-PBPAIR
Error-Introduced Video Encoding, which can still satisfy a given PSNR,and further maximize the energy saving compared to PBPAIR
Intra_Th(KNOB)
Intra MB
Intentional EIR(KNOB)
I-FS
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
System Prototype + NS2
DIPES '08 #38
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Adaptive EE-PBPAIR
DIPES '08 #39
Copyright © 2008 UCI ACES Laboratory http://www.cecs.uci.edu/~aces
Adaptive EE-PBPAIR
DIPES '08 #40