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ECEN4533 Data Communications Lecture #39 15 April 2013 Dr. George Scheets

ECEN4533 Data Communications Lecture #39 15 April 2013 Dr. George Scheets. Problems: 6.1, Web 30-32 Corrected Quizzes due 1 week after return (DL) Corrected tests due 17 April (Live) Final Exam 0800 – 0950, Friday, 3 May (Live) On or before Friday, 10 May (DL)

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ECEN4533 Data Communications Lecture #39 15 April 2013 Dr. George Scheets

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  1. ECEN4533 Data CommunicationsLecture #39 15 April 2013Dr. George Scheets • Problems: 6.1, Web 30-32 • Corrected Quizzes due 1 week after return (DL) • Corrected tests due 17 April (Live) • Final Exam • 0800 – 0950, Friday, 3 May (Live) • On or before Friday, 10 May (DL) • Wireshark Project due by midnight 4 May (All) • Late turn in NOT accepted • 15 points + 20 points extra credit

  2. ECEN4533 Data CommunicationsLecture #40 17 April 2013Dr. George Scheets • Read 17.1 – 17.3 • Problems: 2010 Final Exam • Corrected tests due 17 April (Live) • Final Exam • 0800 – 0950, Friday, 3 May (Live) • On or before Friday, 10 May (DL) • Wireshark Project due by midnight 4 May (All) • Late turn in NOT accepted • 15 points + 20 points extra credit

  3. ECEN4533 Data CommunicationsLecture #41 19 April 2013Dr. George Scheets • Read 17.4 – 17.6 • Problems: 2011 Final Exam • Final Exam • 0800 – 0950, Friday, 3 May (Live) • On or before Friday, 10 May (DL) • Wireshark Project due by midnight 4 May (All) • Late turn in NOT accepted • 15 points + 20 points extra credit

  4. Red, Green, & Blue used on Monitors

  5. Electronics Color Video Monitor Camera R R G G Electronics B B 3 drive signals 3 Pick-Up Elements CCD’s Receiver electronics generate 3 signals with strength proportional to light falling on the 3 camera pick-up elements.

  6. Paints are Subtractive

  7. 24 bit color 224 = 16.78 M colors

  8. 256 Colors

  9. 16 Colors

  10. Video Delivery: Over the Air 300 m ATSC Digital FDM Since June 2009(FCC edict) 40-50 miles

  11. Video Delivery Systems • Cable TV • Tree configuration • Distribution systems originally all coax • Originally Analog NTSC • BW ≈ 700 MHz AMP ... AMP Headend ... AMP ... Initially Simplex Copper Coax

  12. Filtering Scan Line (Time Domain) 2 2 0 1 0 20 40 60 80 100 120 140 0 i 127 Monitor Image

  13. Filtering Scan Line (Frequency Domain) 4 4 X 2 j 0 0 10 20 30 40 50 60 70 0 j 64 1/2 the points thrown out (values < .1) Scan Line (Frequency Domain after zeroing) 4 4 Y 2 j 0 0 0 10 20 30 40 50 60 70 0 j 64

  14. Filtering Reconstructed Scan Lines (Time Domain after filtering) 2 2 1 y i 0 0.086 1 0 20 40 60 80 100 120 140 0 i 127 Using NxN pixel blocks localizes distortion to NxN area, unlike this example. Monitor Image

  15. Dick Tracy with Wrist Radio This is a small JPEG image that's been enlarged. With a good contrast monitor, you should be able to see evidence of the blocks, and should also note that the distortion tends to be localized to areas where the picture is changing.

  16. JPEG Distortion Note the fuzzy gray 'cloud'.

  17. Morse Code:An UnequalLength CodeAverage bit rate is < fixed length code (6 bits/character for the alphabet ifusing fixed lengthcode) Image Source: Wikipedia

  18. Huffman CoderUnequal Length Code WordsHigh Probability? Assign Small Word. • Suppose have 4 voltages to move: • -3 v 25%-1 v 5%+1 v 40%+3 v 30% Huffman Code 111 110 0 10 2 bit code word 11 10 00 01 1,000,000 voltages/sec → 2,000,000 bps (2 bit code) 1,000,000 voltages/sec → 1,900,000 bps (Huffman) .25(3) +.05(3) + .40(1) + .30(2) = 1.9 bits/voltage on average Uniquely Decodable: 1110010110 = ?

  19. David A. Huffman • 1953 PhD Thesis @ M.I.T.

  20. MPEG Video Frame Sequence 1/30th second Predicted Pictures Mostly change since previous I or P frame Bi-directional Pictures Mostly use Motion Estimation Techniques Intrapictures (JPEG Still)

  21. Harry Nyquist • Ph.D. Yale 1917 • Bell Labs 1917 - 1954

  22. ISI due to Brick-Wall Filtering 4.5 smearing z k 0 z2 k Equalizer can undo some of this. 4.5 0 20 40 60 80 100 120 140 0 k 127

  23. Representative Video Bit Rates (Hi ↓ Lo Quality) • 1.2 Gbps Uncompressed HDTV • 19.4 Mbps ATSC ( ≈ HDTV quality) • 8 - 9 Mbps MPEG4 ( ≈ HDTV quality) • 90 Mbps Uncompressed NTSC (SDTV) • 3 - 6 Mbps MPEG2 ( ≈ SDTV quality) • 1.5 Mbps MPEG4 ( ≈ SDTV quality) • 1.5 Mbps MPEG1 ( ≈ VHS < SDTV quality) • Note: ATSC, MPEG2, & MPEG4 support a wide variety of formats (SDTV ↔ HDTV)

  24. Representative Video Bit Rates (Hi ↓ Lo Quality) • 1.2 Gbps Uncompressed HDTV • 19.4 Mbps ATSC ( ≈ HDTV quality) • 8 - 9 Mbps MPEG4 ( ≈ HDTV quality) • 90 Mbps Uncompressed NTSC (SDTV) • 3 - 6 Mbps MPEG2 ( ≈ SDTV quality) • 1.5 Mbps MPEG4 ( ≈ SDTV quality) • 1.5 Mbps MPEG1 ( ≈ VHS < SDTV quality) • How Much More Compression is Still Possible? • H.264 uses 30% less bits than MPEG4 • November 2008 IEEE Communications Magazine

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