Copyright © 2008 UCI ACES Laboratory aces Kyoungwoo Lee, Minyoung Kim, Nikil Dutt, and Nalini...

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


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


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


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


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



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


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



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


Error-Resilient Techniques

Insert Intra-frames (I-frames) periodically

DIPES '08 #10


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)


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


f1

f4f3

f2


f1

f3f2


Outline

Motivation

Our SolutionError-Exploiting Video EncodingEE-PBPAIR

Experiments

Conclusion


Our Proposal

Error-exploiting video encoder Intentional frame dropping + error-resilient video

encoding Extends the tradeoff space for energy consumption /

QoS

DIPES 08 #13


Error-Resilient Video Encoder

DIPES 08 #14

Error-ResilientEncoder

Error-Resilient Video Encoder

OriginalVideoData

Error-Resilient

VideoData

Parameters



DIPES 08 #15

ErrorController



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


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


f1

f4f3

f4 is lost

Error-ProneNetwork

f1f3

IntentionalFrame Dropping

PBPAIR

EE-PBPAIR


f2 is dropped


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



Outline

Motivation

Our Solution

Experiments

Conclusion


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


Mobile Video Decoding

Experimental Setup

DIPES 08 #20

EncoderEncoder TransmitTransmit DecoderDecoderReceiveReceiveNetwork

NS2System Prototype

System Prototype


CPU energy for encodingvideo quality (frame drop)

WNI energy for transmitWNI energy for receive

CPU energy for decodingvideo quality (packet loss)


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


Experimental Results

Energy Reduction from Active Error ExploitationExtended Energy/QoS Tradeoff

DIPES 08 #22


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



Experimental Results

Energy Reduction from Active Error ExploitationExtended Energy/QoS Tradeoff

DIPES 08 #24


Extended Tradeoff Space

DIPES '08 #25

PLR = 5% and EIR = 0% to 50%

EE-PBPAIR extends interesting tradeoff spaces


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%


Outline

Motivation

Our Solution

Experiments

Conclusion


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


Thanks!

Any Questions?

[email protected]


Backup Slides


Intentional Frame Drop and Packet Loss

DIPES '08 #31


Packet Loss

Intentional frame drop


EE-PBPAIR

DIPES '08 #32


Packet Loss

Intentional frame

dropError-Exploiting Video Encoder


(e.g., PBPAIR)

Error-Controller(e.g., frame dropping)Error-Controller

(e.g., frame dropping)

OriginalVideo

Error-Resilient

Video

Error-AwareVideo


Error Controller

DIPES '08 #33


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


f1

f4f3

f2


f1

f3f2


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


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


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


System Prototype + NS2

DIPES '08 #38


Adaptive EE-PBPAIR

DIPES '08 #39


Adaptive EE-PBPAIR

DIPES '08 #40

Copyright © 2008 UCI ACES Laboratory aces Kyoungwoo Lee, Minyoung Kim, Nikil Dutt, and Nalini...

Documents

Transcript of Copyright © 2008 UCI ACES Laboratory aces Kyoungwoo Lee, Minyoung Kim, Nikil Dutt, and Nalini...