ECEN4533 Data CommunicationsLecture #39 15 April 2013Dr. George Scheets

Problems: 6.1, Web 30-32Problems: 6.1, Web 30-32 Corrected Quizzes due 1 week after return (DL)Corrected Quizzes due 1 week after return (DL) Corrected tests due 17 April (Live) Corrected tests due 17 April (Live) Final ExamFinal Exam

0800 – 0950, Friday, 3 May (Live)0800 – 0950, Friday, 3 May (Live) On or before Friday, 10 May (DL)On or before Friday, 10 May (DL)

Wireshark Project due by midnight 4 May (All)Wireshark Project due by midnight 4 May (All) Late turn in NOT acceptedLate turn in NOT accepted 15 points + 20 points extra credit15 points + 20 points extra credit

ECEN4533 Data CommunicationsLecture #40 17 April 2013Dr. George Scheets

Read 17.1 – 17.3Read 17.1 – 17.3 Problems: 2010 Final ExamProblems: 2010 Final Exam Corrected tests due 17 April (Live) Corrected tests due 17 April (Live) Final ExamFinal Exam

0800 – 0950, Friday, 3 May (Live)0800 – 0950, Friday, 3 May (Live) On or before Friday, 10 May (DL)On or before Friday, 10 May (DL)

Wireshark Project due by midnight 4 May (All)Wireshark Project due by midnight 4 May (All) Late turn in NOT acceptedLate turn in NOT accepted 15 points + 20 points extra credit15 points + 20 points extra credit

ECEN4533 Data CommunicationsLecture #41 19 April 2013Dr. George Scheets

Read 17.4 – 17.6Read 17.4 – 17.6 Problems: 2011 Final ExamProblems: 2011 Final Exam Final ExamFinal Exam

0800 – 0950, Friday, 3 May (Live)0800 – 0950, Friday, 3 May (Live) On or before Friday, 10 May (DL)On or before Friday, 10 May (DL)

Wireshark Project due by midnight 4 May (All)Wireshark Project due by midnight 4 May (All) Late turn in NOT acceptedLate turn in NOT accepted 15 points + 20 points extra credit15 points + 20 points extra credit

Red, Green, & Blue used on Monitors

Color Video

Ele

ctro

nics

3 Pick-Up Elements

CCD’s

R

G

B

Camera

Ele

ctro

nics

R

G

B

3 drivesignals

Monitor

Receiver electronics generate 3 signals withstrength proportional to light falling on the 3 camera pick-up elements.

Paints are Subtractive

24 bit color 224 = 16.78 M colors

256 Colors

16 Colors

Video Delivery: Over the Air

300 mATSC

Digital FDMSince June 2009

(FCC edict)

40-50 miles

Video Delivery Systems Cable TV

Tree configuration Distribution systems originally all coax Originally Analog NTSC BW ≈ 700 MHz

HeadendAMP

AMP

...

...

AMP

...

Initially Simplex Copper Coax

Filtering

0 20 40 60 80 100 120 140

0

22

1

1270 i

Scan Line (Time Domain)

Monitor Image

Filtering

0 10 20 30 40 50 60 700

2

44

X j

640 j

Scan Line (Frequency Domain)

Scan Line (Frequency Domain after zeroing)

0 10 20 30 40 50 60 700

2

44

0

Y j

640 j

1/2 the points thrown out (values < .1)

FilteringReconstructed Scan Lines (Time Domain after filtering)

0 20 40 60 80 100 120 1401

0

1

22

0.086

y i

1270 i

y

Monitor Image

Using NxNpixel blockslocalizesdistortion to NxN area,unlike thisexample.

Dick Tracy with Wrist RadioThis is a small JPEG imagethat's been enlarged.

With a good contrast monitor, you should be able to see evidence of theblocks, and should alsonote that the distortion tends to be localized to areas where the picture is changing.

JPEG Distortion

Note the fuzzygray 'cloud'.

Morse Code:An UnequalLength Code

Average bit rate is < fixed length code (6 bits/character for the alphabet ifusing fixed length

code)

Image Source:Wikipedia

Huffman CoderUnequal Length Code Words

High Probability? Assign Small Word. Suppose have 4 voltages to move:Suppose have 4 voltages to move:

-3 v-3 v 25%25%-1 v-1 v 5% 5%+1 v+1 v 40%40%+3 v+3 v 30%30%

2 bit code word11100001

Huffman Code111110

010

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 = ?

David A. Huffman

1953 PhD Thesis @ M.I.T.1953 PhD Thesis @ M.I.T.

MPEG Video Frame Sequence1/30th second

Intrapictures (JPEG Still)

Bi-directional PicturesMostly use

Motion EstimationTechniques

Predicted PicturesMostly changesince previousI or P frame

Harry Nyquist

Ph.D. Yale 1917Ph.D. Yale 1917 Bell Labs 1917 - 1954Bell Labs 1917 - 1954

ISI due to Brick-Wall Filtering

0 20 40 60 80 100 120 140

0

4.5

4.5

zk

z2k

1270 k

smearing

Equalizer can undo some of this.

Representative Video Bit Rates

(Hi ↓ Lo Quality) 1.2 Gbps Uncompressed HDTV1.2 Gbps Uncompressed HDTV 19.4 Mbps ATSC ( ≈ HDTV quality)19.4 Mbps ATSC ( ≈ HDTV quality) 8 - 9 Mbps MPEG4 ( ≈ HDTV quality)8 - 9 Mbps MPEG4 ( ≈ HDTV quality) 90 Mbps Uncompressed NTSC (SDTV) 90 Mbps Uncompressed NTSC (SDTV) 3 - 6 Mbps MPEG2 ( ≈ SDTV quality)3 - 6 Mbps MPEG2 ( ≈ SDTV quality) 1.5 Mbps MPEG4 ( ≈ SDTV quality)1.5 Mbps MPEG4 ( ≈ SDTV quality) 1.5 Mbps MPEG1 ( ≈ VHS < SDTV quality)1.5 Mbps MPEG1 ( ≈ VHS < SDTV quality) Note: ATSC, MPEG2, & MPEG4 support a Note: ATSC, MPEG2, & MPEG4 support a widewide variety of formats (SDTV ↔ HDTV) variety of formats (SDTV ↔ HDTV)

Representative Video Bit Rates

(Hi ↓ Lo Quality) 1.2 Gbps Uncompressed HDTV1.2 Gbps Uncompressed HDTV 19.4 Mbps ATSC ( ≈ HDTV quality)19.4 Mbps ATSC ( ≈ HDTV quality) 8 - 8 - 9 Mbps MPEG4 ( ≈ HDTV quality)9 Mbps MPEG4 ( ≈ HDTV quality) 90 Mbps Uncompressed NTSC (SDTV) 90 Mbps Uncompressed NTSC (SDTV) 3 - 6 Mbps MPEG2 ( ≈ SDTV quality)3 - 6 Mbps MPEG2 ( ≈ SDTV quality) 1.5 Mbps MPEG4 ( ≈ SDTV quality)1.5 Mbps MPEG4 ( ≈ SDTV quality) 1.5 Mbps MPEG1 ( ≈ VHS < SDTV quality)1.5 Mbps MPEG1 ( ≈ VHS < SDTV quality) How Much More Compression is Still Possible?How Much More Compression is Still Possible?

H.264 uses 30% less bits than MPEG4H.264 uses 30% less bits than MPEG4 November 2008 IEEE Communications MagazineNovember 2008 IEEE Communications Magazine