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Error-Exploiting Video Encoder to Extend Energy/QoS Tradeoffs for Mobile Embedded Systems

Error-Exploiting Video Encoder to Extend Energy/QoS Tradeoffs for Mobile Embedded Systems. Kyoungwoo Lee, Minyoung Kim, Nikil Dutt, and Nalini Venkatasubramanian. Department of Computer Science University of California at Irvine. Outline. Motivation Our Solution Experiments Conclusion.

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Error-Exploiting Video Encoder to Extend Energy/QoS Tradeoffs for Mobile Embedded Systems

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  1. Error-Exploiting Video Encoder to Extend Energy/QoS Tradeoffs for Mobile Embedded Systems Kyoungwoo Lee, Minyoung Kim, Nikil Dutt, and Nalini Venkatasubramanian Department of Computer Science University of California at Irvine

  2. Outline • Motivation • Our Solution • Experiments • Conclusion

  3. Energy Reduction is Essential • Mobile computing is popular Business Communication, Entertainment, & Education Battlefield Wellness Science Resource-limited mobile devices! Fundamental problem is to achieve low power with high performance

  4. Mobile Video Applications EE DCT Q ME f4 f3 f2 f1 Network Mobile Video Applications Essential to extend the tradeoff space of energy consumption and QoS • Mobile video applications demand high energy consumption • Complex video encoding/decoding algorithms • Transmitting huge volume of video data DIPES '08 #4

  5. Energy/QoS Video Encodings Our solution – Active Error Exploitation to reduce the energy consumption for video encoding • Energy/QoS-aware video encoding • Video 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 Resilience • PBPAIR (Probability-Based Power Aware Intra Refresh) – error-resilient and energy-efficient [Kim, MCCR06]  Passive Error Exploitation DIPES 08 #5

  6. Active Error Exploitation • Active Error Exploitation – Intentional Frame Dropping • Skip the expensive video encoding algorithm  Energy saving • Degrade the video quality • Inherent error-tolerance mitigates the impact of frame drops on video quality Network Mobile Video Applications f4 f3 f2 f1

  7. Frame Drop Types Mobile Video Application • FDT-1 affects the following components with respect to power, performance, and QoS in mobile video applications • This work studies FDT-1, and future work includes FDT-2 and FDT-3 Enc Tx Rx Dec FDT-1 FDT-2 FDT-3 CPU WNI WNI CPU • FDT: Frame Drop Type • Enc: Encoding, Dec: Decoding • WNI: Wireless Network Interface Packet Loss Error-prone Networks

  8. Frame Losses due to Packet Losses Mobile Video Applications • Inherent Error-Tolerance of Video Data • Error-Resilient/Error-Concealment Techniques f3 f2 f1 Error-Prone Network f4 is lost Error-Induced Video Data f4 f3 f2 f1

  9. Inherent Error-Tolerance of Video Data • Error-Tolerance of Video Data • Spatial and temporal correlation among consecutive video frames • Lossy video encoding • (e.g.) High Quantization Scale • Energy Reduction and Error-Tolerance • Error-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 second Mobile Video Encoding DCT EE Q ME f4 f3 f2 f1 ME – Motion Estimation DCT – Discrete Cosine Transform Q – Quantization EE – Entropy Encoding

  10. Error-Resilient Techniques f3 f2 f1 • Insert Intra-frames (I-frames) periodically Error-Prone Network f4 is lost Error-Induced Video Data • 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 techniques • AIR (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) f4 f3 f2 f1

  11. Energy Efficiency f3 f2 • 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 f1 Error-Prone Network f4 is lost Error-Induced Video Data f4 f3 f2 f1

  12. Outline • Motivation • Our Solution • Error-Exploiting Video Encoding • EE-PBPAIR • Experiments • Conclusion

  13. Our Proposal • Error-exploiting video encoder • Intentional frame dropping + error-resilient video encoding • Extends the tradeoff space for energy consumption / QoS

  14. Error-Resilient Video Encoder Error-Resilient Video Encoder Error- Resilient Video Data Original Video Data Error-Resilient Encoder Parameters

  15. Error-Exploiting Video Encoder Combined approach may consume less energy Error-Exploiting Video Encoder Error- Injected Video Data Error- Aware Video Data Original Video Data Error-Injecting Unit Error-Canceling Unit Error Controller Error-Resilient Encoder Reduce Energy Consumption Constraints Parameters Incur Energy Overhead & Feedback

  16. Intentional Frame Dropping and PBPAIR f3 f1 • Energy Efficiency • Frame Dropping • (e.g.) f2 is dropped • PBPAIR Error-Prone Network f4 is lost f2 is dropped Error-Induced Video Data EE-PBPAIR Error-Canceling Unit Error-Injecting Unit Intentional Frame Dropping PBPAIR • Quality Management • Error-Resilience • (e.g.) EE-PBPAIR encodes video data resilient against f2 and f4 • Error-Tolerance f4 f3 f1

  17. EIR – Error Injection Rate EE-PBPAIR Error- Aware Video Data • EIR adjusts the rate of intentional frame dropping • EIR is Frame Drop Rate at Error-Injecting Unit • EIR is translated for PBPAIR (considering it as PLR) • Feedback-based quality adjustment • High EIR increases energy saving but degrades video quality Original Video Data Error-Injecting Unit Error-Canceling Unit Frame Dropping PBPAIR Quality Constraint and Quality Feedback Parameters EIR

  18. Outline • Motivation • Our Solution • Experiments • Conclusion

  19. End-to-End Experimental Framework • End-to-End Experimental Framework • Mobile 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 Simulator • System 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 Simulator • Estimates the energy consumption of WNI (transmission power)

  20. Experimental Setup Mobile Video Decoding Mobile Video Encoding Decoder Receive Transmit Encoder Network System Prototype System Prototype NS2 CPU energy for decoding video quality (packet loss) CPU energy for encoding video quality (frame drop) WNI energy for transmit WNI energy for receive

  21. Evaluation • Video Encoding • GOP-K (Group-Of-Picture with K) • PBPAIR (Probability-Based Power Aware Intra Refresh) • EE-PBPAIR (Error-Exploiting PBPAIR) • Energy Consumption • Enc EC (Energy Consumption for Encoding) + Tx EC (Energy Consumption for Transmission) • Rx EC (Energy Consumption for Receiving) + Dec EC (Energy Consumption for Decoding) • Video Quality • Video Quality at encoder after intentional frame dropping • Video Quality at decoder after packet losses in networks

  22. Experimental Results • Energy Reduction from Active Error Exploitation • Extended Energy/QoS Tradeoff

  23. Energy Saving Mobile Video Decoding Mobile Video Encoding Decoder Receive Transmit Encoder Network EC = Energy Consumption Enc EC = EC for Encoding Tx EC = EC for Transmission Dec EC = EC for Decoding Rx EC = EC for Receiving • PLR = 10% and EIR = 10% Energy saving occurs at every component in a path from encoding to decoding in mobile video applications • PSNR: Peak Signal to Noise Ratio

  24. Experimental Results Energy Reduction from Active Error Exploitation Extended Energy/QoS Tradeoff DIPES 08 #24

  25. Extended Tradeoff Space • PLR = 5% and EIR = 0% to 50% EE-PBPAIR extends interesting tradeoff spaces

  26. Energy Reduction at QoS Cost At 10% cost of video quality, EE-PBPAIR can save the energy consumption of Enc and Tx by up to 49%

  27. Outline • Motivation • Our Solution • Experiments • Conclusion

  28. 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

  29. Thanks! Any Questions? kyoungwl@ics.uci.edu

  30. Backup Slides

  31. Intentional Frame Drop and Packet Loss Intentional frame drop Packet Loss Error-prone Networks

  32. EE-PBPAIR Intentional frame drop Packet Loss Error-Exploiting Video Encoder Error- Resilient Video Error- Aware Video Original Video Error-Controller (e.g., frame dropping) Error-Resilient Encoder (e.g., PBPAIR) EIR Error-prone Networks

  33. Error Controller

  34. Error-Concealment f3 f2 • Error-Concealment Techniques • Interpolate the lost frame using near frames • Substitute the near frame for the lost one • (e.g.) f2 is copied for f3 (the lost one) in displaying frames f1 Error-Prone Network f4 is lost Error-Induced Video Data f4 f3 f2 f1

  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 GOP Intra Frame Static Constraint of Compression Rate IP-ratio (KNOB) Standard video encoding, which is unaware of energy consumption and error-resiliency

  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 PBPAIR Intra MB PLR from Network Channel Intra_Th (KNOB) Error-Resilient Encoding, which can satisfy a given PSNR, and reduce the energy consumption for encoding

  37. EE-PBPAIR • EE-PBPAIR introduces another KNOB (intentional EIR) other than Intra_Th, and can further save the energy consumption Encoder EE-PBPAIR Intra MB PLR from Network Channel I-FS Intentional EIR (KNOB) Intra_Th (KNOB) Error-Introduced Video Encoding, which can still satisfy a given PSNR, and further maximize the energy saving compared to PBPAIR

  38. System Prototype + NS2

  39. Adaptive EE-PBPAIR

  40. Adaptive EE-PBPAIR DIPES '08 #40

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