1. 1 TTM4142 Networked Multimedia Systems Video Basics Image and Video Lossless Compression Leif Arne Rønningen Autumn 2008

2. 2 Graphics and Image Data Representations Large number of (file) formats, PDF, JPEG, GIF, PNG, BMP 8 bit Gray-Level Images 24 bit Color Images, RGB Color Lookup Table - LUT Dithering

3. 3 Color in Image and Video Spectral power distribution of daylight Wavelength (nm)

4. 4 Human Vision

5. 5 CIE tristimulus values

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7. 7 Color Models in Video YUV – PAL and CCIR 601 digital video YCrCb – JPEG, MPEG, ITU-R 601-4

8. 8 Fundamental Video Concepts Component Video, RGB, YUV, YCrCb Composite Video, chrominance and luminance signals on single carrier S-Video, separated video, one wire for luminance, one wire for composite chrominance Analog Video, PAL, interlaced scan, blanking intervals h, v Digital Video, YCrCb - chroma subsampling

9. 9 Digital Video

10. 10 HDTV H.264, (MPEG-4 part 10)

11. 11 Lossless Compression Algorithms Information theory Alphabet S = Entropy

12. 12 Run-length Coding The string AABACCCCCCCCCCDEAB can be coded as !02ABA!10CDEAB Which is 14 instead of 18 characters ! Must be reserved

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15. 15 LZW Compression With this algorithm, the encoder and decoder build up the same dictionary of recognized strings from a stream dynamically. Each string is given a codeword. The encoder sends short codewords instead of long strings. See Li and Drew for details

16. 16 Arithmetic Coding, Sequence to be coded: CAEE$

17. 17 Arithmetic Coding

18. 18 Arithmetic Coding, Decoding The coded sequence CAEE$ ends up with the interval [0.33184, 0.3322) Find the shortest binary number that is within this interval, 0.01010101 0.33203125 (procedure 7.2 in book) Note that only 8 bits is needed! For decoding, go the opposite way of that in the previous slide 0.33203125 is in Low-High interval for C (0.33203125-0.3)/0.2 = 0.16015624, an A and so on

19. 19 Comparing some lossless compression schemes