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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