Power analysis of H.264/AVC for mobile platforms


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This is the presentation for the defense of my master thesis in Computer Engineering

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Power analysis of H.264/AVC for mobile platforms

  1. 2. Power analysis of H.264/AVC for mobile platforms Student: Alexandru IOVANOVICI, B.Eng. Supervisor: Lucian PRODAN, Ph.D, B.Eng. Master’s Thesis June 2011
  2. 3. What ... is the problem ? 1. Customers are mobile 2. Customers expect PC-like features from their „cell-phones”
  3. 4. What ... solutions do we have ? CODECs
  4. 5. Video CODECs basics <ul><li>RAW video -> minimum 216Mbps [Richardson2010] </li></ul><ul><li>Lossless compression = removing data redundancy (3-4 times less space); </li></ul><ul><li>Lossy compression = removing subjective redundancy; much higher compression rates; </li></ul>
  5. 6. Video ENCODER basics <ul><li>Prediction model: </li></ul><ul><li>exploiting the similarities between neighbouring video frames; </li></ul><ul><li>Spatial model: </li></ul><ul><li>compressing the residual; transform coeficients; </li></ul><ul><li>Entropy encoder: </li></ul><ul><li>removing statistical redundancy; </li></ul>
  6. 7. Typical ENCODER architecture <ul><li>DPCM/DCT architecture: basis for all modern encoders, including H.264 ; </li></ul>
  7. 8. Typical DECODER architecture
  8. 9. The H.264/AVC <ul><ul><li>H.264/AVC gives specifications only for the decoder; </li></ul></ul><ul><ul><li>Published by ITU in 2003 with several revisions; </li></ul></ul><ul><ul><li>Based on MPEG-4 Visual; </li></ul></ul><ul><ul><li>10 to 50 times better compression ratio at same visual quality [Richardson2010, Xe2007] </li></ul></ul><ul><ul><li>2 to 10 times more power dissipation than MPEG-4 [Xe2007] </li></ul></ul>
  9. 10. The H.264 ENCODER
  10. 11. Transform and quantization
  11. 12. H.264 Profiles <ul><li>There is a great flexibility in choosing the apropriate combination of tools that best suit the specific needs of a particular tasks [eg. CAVLC+DCT]; </li></ul><ul><li>H.264 profiles define a specific set of tools; </li></ul><ul><li>A profile compliant decoder must be able to decode with all the tools in that profile -> constraints on the capabilities required by a decoder; </li></ul>
  12. 13. The Zexia encoder <ul><li>Non-interlaced Base Profile ; </li></ul><ul><li>Only OpenSource available encoder for H.264; </li></ul><ul><li>Modular, interface-based; </li></ul><ul><li>VHDL configuration-based; </li></ul><ul><li>Better suited for Spartan 3 than for Cyclone III: Spartan has more on-chip memory ; </li></ul><ul><li>Two Clock lines; </li></ul>
  13. 14. <ul><li>RAM: an entire image must be loaded by the external controller ; and the reference image too; </li></ul><ul><ul><li>Smaller reqirements if we use intraprediction only [Richardson2007]; </li></ul></ul><ul><li>Predictions components: </li></ul><ul><ul><li>SAD comparaison; </li></ul></ul><ul><ul><li>Only p-frames prediction (licensing issues); </li></ul></ul>The Zexia encoder
  14. 15. <ul><li>Simulation based – lack of hardware resources on Altera DE2 board; </li></ul><ul><li>Quartus II with Advanced PowerPlay Early Estimator; </li></ul><ul><li>VCD files based on statistical distribution of line transitions (12.5% [Xe2007]). </li></ul>Experimental results
  15. 16. Experimental results
  16. 17. Experimental results FPGAs are bad at low-power optimizations
  17. 18. Augmented Cell Phone A new architecture <ul><li>Coprocessor based cell-phone; </li></ul><ul><li>“ Program repository” on Flash; </li></ul><ul><li>Marketplace for “programs”; </li></ul><ul><li>High power requirements but even higher customer satisfaction </li></ul><ul><ul><li>better user experience ; </li></ul></ul><ul><li>-> more devices sold; </li></ul>
  18. 19. Conclusions <ul><li>H.264 is a power intensive algorithm; </li></ul><ul><ul><li>Less than 30% is parallel [52]; </li></ul></ul><ul><ul><li>ASIC is the best option but is „expensive”; </li></ul></ul><ul><li>FPGAs are not good for low-power techniques </li></ul><ul><ul><li>Large routing grids; </li></ul></ul><ul><ul><li>A lot of cells are powered on even in neutral functions; </li></ul></ul><ul><ul><li>Good for comparing two similar designs in HDL in terms of simulated performance; </li></ul></ul><ul><li>ACP : balance between power requirements and user satisfaction </li></ul><ul><ul><li>Need considerable rethinking on the HW level and the OS; </li></ul></ul><ul><ul><li>Need skilled developers for “soft-coprocessors” </li></ul></ul>