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Time to Enhance JPEG-1

Time to Enhance JPEG-1. Dr. Joan L. Mitchell IBM Fellow, IBM Printing Systems Division, Boulder, CO. Outline. JPEG-1 parts Enhancement to JPEG-1 (T.851) Call for interested parties Potential enhancements. JPEG-1 parts. Part 1: ITU-T Rec. T.81|ISO/IEC 10918-1 Requirements and Guidelines

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Time to Enhance JPEG-1

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  1. Time to Enhance JPEG-1 Dr. Joan L. Mitchell IBM Fellow, IBM Printing Systems Division, Boulder, CO

  2. Outline • JPEG-1 parts • Enhancement to JPEG-1 (T.851) • Call for interested parties • Potential enhancements

  3. JPEG-1 parts • Part 1: ITU-T Rec. T.81|ISO/IEC 10918-1 Requirements and Guidelines • Part 2: ITU-T Rec. T.83|ISO/IEC 10918-2 Compliance tests • Part 3: ITU-T Rec. T.84|ISO/IEC 10918-3 Extensions • Part 4: ITU-T Rec. T.86(?)|ISO/IEC 10918-4 Registration authority

  4. Modes of JPEG-1 • Baseline Sequential (DCT-based, Huffman) • Extended Sequential • Progressive • Spectral selection • Successive approximation • Hierarchical • Change sizes by factors of 2 • Improve quality • Lossless (not DCT-based)

  5. Entropy coders in JPEG-1 • Huffman • Fixed (example tables) • Custom (2 pass adaptive) • Arithmetic coding • QM-coding (1 pass adaptive) • 3 patent holders (IBM, MEL, AT&T) • $5/15K each

  6. A.C. vs. Huffman coding • Both lossless entropy coders • Bit errors not allowed • Huffman coding • Custom table optimal for integer bits/code • Assumes static statistics over image • Arithmetic coding • Adaptive FSM estimation of statistics • Slower than Huffman coding (approx 2:1) • Net 25% more CPU cycles in 1989

  7. Enhancement to JPEG-1 T.851 • Bit depth for DCT 8-16 • Q-15 coder * • Fee-free (IBM IP only) • Based on JPEG 8 ver. 5.2 (1990) • 5-20% compression improvements • Successive approximation easier • JPEG Extension (JPG) marker * • Replaces Start of Image (SOI) marker • Allows for future extensions variations * Likely to be in IJG code version 8

  8. T.851 open source software* • Not ready last year • Mike Slattery, ASICNorth, provided • Originally a patch on IJG code • Now have IJG cooperation • Still waiting on independent validation • Guido Vollbeding appoint webmaster for ITU-T T.851 software website * Likely to be in IJG code version 8 late ‘07

  9. Call for interested parties • Ad Hoc on Exploring Enhancements to JPEG-1 • SG16 WP3/Q23 (April 6-7, 2006) • Joan L. Mitchell (IBM), chair • Guido Vollbeding (IJG) • Recommended: • Call be made for interested parties to attend the next SG16/WP3/Q23 meeting • Understanding/exploring possible enhancements to JPEG-1.

  10. Hope • Items • With clear need • With easy implementations • Be added to T.851 as an annex within a year • Ongoing process • Future annexes in future years(?)

  11. Possible enhancements • Discard rows/columns at top/left edges • Needed for 90 degree rotations • Image cropping off 8x8 block boundaries • Component registration • Location of sub-sampled components • MPEG-1: centered in 2x2 block • MPEG-2: co-located H, centered V • Standardized IDCT(s) (lossless hierarchical) • Waiting for results of MPEG contest • Requirements relaxed

  12. Improvements to lossless • Quantization of lossless prediction • DC progressive • Use 2-D lossless • Use near lossless • More contexts for DC/Lossless A.C. • Doubling contexts (25->49) gives 5% improvement • No extra CPU cycles in inner loop

  13. Alternate scan orders • Along vertical/horizontal (not diagonal) 0 1 8 9 24 25 48 49 3 2 7 10 23 26 47 50 4 5 6 11 22 27 46 51 15 14 13 12 21 28 45 52 16 17 18 19 20 29 44 53 35 34 33 32 31 30 43 54 36 37 38 39 40 41 42 55 63 62 61 60 59 58 57 56 • Custom scan order (LUT to decoder)

  14. Specialized Scaling Up|Down • Specialized FDCT/IDCTs for scaling * • Ex: specialized IDCTs I • Scale up 9x9,… 16x16 • Scale down 7x7,… 1x1 • Alternate scan order assists • Lossless via DC (no longer in IJG code) • Encoder 8x8 scaled up image, only DC • Decoder scales down 8x8. * Implemented in IJG code version 7

  15. Not a new competition • Looking for minor tweaks • JPEG-1 designed for minimum of 25 years • Reasonable to have some maintenance • ITU-T SG16/WP3/Q23 asking the question • Need more company/country participation • Won’t happen if no interest • I’m willing to be the editor • Please help get the word out

  16. Q & A

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