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The JPEG Standard

The JPEG Standard. J. D. Huang Graduate Institute of Communication Engineering National Taiwan University, Taipei, Taiwan, ROC. 1. Introduction. JPEG standard is a collaboration among : International Telecommunication Union (ITU) International Organization for Standardization (ISO)

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The JPEG Standard

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  1. The JPEG Standard J. D. Huang Graduate Institute of Communication Engineering National Taiwan University, Taipei, Taiwan, ROC

  2. 1. Introduction • JPEG standard is a collaboration among : • International Telecommunication Union (ITU) • International Organization for Standardization (ISO) • International Electrotechnical Commission (IEC) • The official names of JPEG : • Joint Photographic Experts Group • ISO/IEC 10918-1 Digital compression and coding of continuous-tone still image • ITU-T Recommendation T.81 Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  3. 1. Introduction • JPEG have the following mods : • Lossless mode, predictive coding • Sequential mode, DCT-based coding • Progressive mode, DCT-based coding • Hierarchical mode • Baseline system • Sequential mode, DCT-based coding, Huffman coding for entropy encoding • The most widely used mode in practice Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  4. 1. Introduction HuffmanTable AC Zig-zag reordering Huffmancoding Color components(Y, Cb, or Cr) 88 FDCT Quantizer JPEGbit-stream DifferenceEncoding Huffmancoding DC QuantizationTable HuffmanTable Figure 1. Baseline JPEG encoder Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  5. 2. Color Space Conversion (a) translate from RGB to YCbCr (b) translate from YCbCr to RGB Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  6. 3. Downsampling W W W Y Y Y H H H W W W Cb Cb Cb H H H W W W Cr Cr Cr H H H (a) 4:4:4 (b) 4:2:2 (c) 4:2:0 Figure 2. Three color format in the baseline system Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  7. 4. Discrete Cosine Transform Forward DCT: Inverse DCT: Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  8. 4. Discrete Cosine Transform u 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 v The 8x8 DCT basis Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  9. 4. Discrete Cosine Transform Example : W Y H the luminance of an image 8x8 values of luminance DCT 8x8 DCT coefficiences Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  10. 5. Quantization Figure 3. Luminance and Chrominance quantization matrix Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  11. 5. Quantization Example : F(u,v) 8x8 DCT coefficiences Q(u,v) Quantization matrix Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  12. 5. Quantization Example : Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  13. 6. Zig-Zag Reordering Figure 4. Zig-Zag reordering matrix Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  14. 6. Zig-Zag Reordering Example : Zig-Zag Reordering : 44, 4,-11, 6,-6,6, 5,-5,2,-3, -9,1,4,-4,1, -1,2,2,-1,-2,4, -1,0,0,-2,0,0,0, 0,0,0,1,0,1,-1,0, -1,0,-1,0,0,0,0, 0,0,0,-1,0,0, 0,1,0,0,0, 0,0,0,0, 0,0,0, 0,0, 0 Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  15. 7. Zero Run Length Coding • Example 1 • 63 AC coefficience: • 57, 45, 0, 0, 0, 0, 23, 0, -30, -16, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0,..., 0 • Run Length Coding : • (0,57) ; (0,45) ; (4,23) ; (1,-30) ; (0,-16) ; (2,1) ; EOB • Example 2 • 63 AC coefficience: • 57, 0, 0, ... , 0, 3, 0, 0, 0, 0, 2, 0, 0, ... , 0, 895, EOB • Run Length Coding : • (0,57) ; (15,0) ; (2,3) ; (4,2) ; (15,0) ; (15,0) ; (1,895) ; (0,0) 50 zeros (0,0) 18 zeros 33 zeros Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  16. 8. Difference Coding Decode : DCi = DCi1 + Diffi Encode : Diffi = DCi DCi1 Diffi1= DCi1 DCi2 Diffi= DCi DCi1 Diff1=DC1 … … DC0 DC1 DCi1 DCi 0 … … block i1 block 1 block i Figure 5. DCs of 88 blocks Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  17. 9. Huffman Coding Figure 6. Table of values and bits for the value Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  18. 9. Huffman Coding • Example Run lenth coding of 63 AC coefficiences : (0,57) ; (0,45) ; (4,23) ; (1,-30) ; (0,-8) ; (2,1) ; (0,0) Encode the right value of these pair as category and bits for the value, except the special markers like (0,0) or (15,0) : (0,6,111001) ; (0,6,101101) ; (4,5,10111); (1,5,00001) ; (0,4,0111) ; (2,1,1) ; (0,0) The difference of DC coefficience : -511 Encode the value as category and bits for the value : 9, 000000000 Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  19. 9. Huffman Coding Figure 7. Huffman table of luminance AC coefficience Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  20. 9. Huffman Coding Figure 8. Huffman table of luminance DC coefficience Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  21. 9. Huffman Coding • Example The AC coefficiences : (0,6,111001) ; (0,6,101101) ; (4,5,10111); (1,5,00001) ; (0,4,0111) ; (2,1,1) ; (0,0) Encode the left two value in () using Huffman encoding : • 1111000 111001 , 1111000 101101 , 1111111110011000 10111 , • 11111110110 00001 , 1011 0111 , 11100 1 , 1010 • The DC coefficience : • 9, 000000000 • Encode the category using Huffman encoding : • 1111110 000000000 Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

  22. End Graduate Institute of Communication Engineering, National Taiwan University, Taipei, Taiwan, ROC

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