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ECEN4533 Data Communications Lecture #3915 April 2013 Dr. George Scheets n Problems: 6.1, Web 30-32 n Corrected Quizzes due 1 week after return (DL) n.

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Presentation on theme: "ECEN4533 Data Communications Lecture #3915 April 2013 Dr. George Scheets n Problems: 6.1, Web 30-32 n Corrected Quizzes due 1 week after return (DL) n."— Presentation transcript:

1 ECEN4533 Data Communications Lecture #3915 April 2013 Dr. George Scheets n Problems: 6.1, Web n Corrected Quizzes due 1 week after return (DL) n Corrected tests due 17 April (Live) n Final Exam u 0800 – 0950, Friday, 3 May (Live) u On or before Friday, 10 May (DL) n Wireshark Project due by midnight 4 May (All) u Late turn in NOT accepted u 15 points + 20 points extra credit

2 ECEN4533 Data Communications Lecture #4017 April 2013 Dr. George Scheets n Read 17.1 – 17.3 n Problems: 2010 Final Exam n Corrected tests due 17 April (Live) n Final Exam u 0800 – 0950, Friday, 3 May (Live) u On or before Friday, 10 May (DL) n Wireshark Project due by midnight 4 May (All) u Late turn in NOT accepted u 15 points + 20 points extra credit

3 ECEN4533 Data Communications Lecture #4119 April 2013 Dr. George Scheets n Read 17.4 – 17.6 n Problems: 2011 Final Exam n Final Exam u 0800 – 0950, Friday, 3 May (Live) u On or before Friday, 10 May (DL) n Wireshark Project due by midnight 4 May (All) u Late turn in NOT accepted u 15 points + 20 points extra credit

4 Red, Green, & Blue used on Monitors

5 Color Video Electronics 3 Pick-Up Elements CCD’s R G B Camera Electronics R G B 3 drive signals Monitor 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 2 24 = M colors

8 256 Colors

9 16 Colors

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

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

12 Filtering i Scan Line (Time Domain) Monitor Image

13 Filtering X j 640j Scan Line (Frequency Domain) Scan Line (Frequency Domain after zeroing) Y j 640j 1/2 the points thrown out (values <.1)

14 Filtering Reconstructed Scan Lines (Time Domain after filtering) y i 1270i Monitor Image Using NxN pixel blocks localizes distortion to NxN area, unlike this example.

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 Unequal Length Code Average bit rate is < fixed length code (6 bits/character for the alphabet if using fixed length code) Image Source: Wikipedia

18 Huffman Coder Unequal Length Code Words High Probability? Assign Small Word. n Suppose have 4 voltages to move: u -3 v25% -1 v 5% +1 v40% +3 v30% 2 bit code word Huffman Code ,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: = ?

19 David A. Huffman n 1953 PhD M.I.T.

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

21 Harry Nyquist n Ph.D. Yale 1917 n Bell Labs

22 ISI due to Brick-Wall Filtering z k z2 k 1270k smearing Equalizer can undo some of this.

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

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

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