ELE 488 F06 ELE 488 Fall 2006 Image Processing and Transmission (11-16-06, 11-21-06) JPEG block based transform coding Beyond basic JPEG Spatial correlation Subband decomposition & coding Wavelet transform Zero tree Successive Approximation Quantization Digital Video 11/16
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ELE 488 F06 ELE 488 Fall 2006 Image Processing and Transmission (11-16-06, 11-21-06) JPEG block based transform coding Beyond basic JPEG Spatial correlation.
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ELE 488 F06
ELE 488 Fall 2006Image Processing and Transmission
(11-16-06, 11-21-06)
JPEG block based transform coding Beyond basic JPEG Spatial correlation Subband decomposition & coding Wavelet transform Zero tree Successive Approximation Quantization
Digital Video
11/16
ELE 488 F06
Review of Up and Down Sampling (without filter)
• Down sampling
• Up sampling
+----+ x[n]-->| ↓ M |--> y[n]=x[nM], +----+
Y(ω) =M
1
1
0
M
r
X(M
r 2).
Example: M = 2 Y(ω) =2
1X(
2
) +
2
1X(
2
)
+----+ u[n]-->| ↑ L |--> v[nL]=u[n] +----+ y[Ln+k]=0,0<k<L V(ω) = U(ωL). Example: L = 2 V(ω) = U(2ω)
ELE 488 F06
0
X(ω)
2/2 0
X(ω/2)
2/2
X(ω/2-)Y(ω)
(A)
0
X(ω)
/22 0
V(ω)
/22
(C)(D)
(B)
Lowpass and Highpass Decimation
+----+ +----+ +------------+ -->| ↓2 |----->| ↑2 |----->| LPF or HPF |--> +----+ +----+ +------------+ x y v x
• 3dB improvement?– Wavelet compression claimed to have 3dB improvement
over DCT-based compression– Comparison done on JPEG Baseline
• Improvement not all due to transforms– Improvement comes mainly from better rate allocation,
advanced entropy coding, & smarter redundancy reduction via zero-tree
– DCT coder can be improved to decrease the gap
"A comparative study of DCT- and wavelet-based image coding" Z. Xiong, K. Ramchandran, M. Orchard, Y-Q. Zhang, IEEE Trans. on Circuits and Systems for Video Tech., Aug 1999, pp692-695.
• Motion pictures started with an argument:– “Do They Or Don’t They?”– Muybridge (1877) - 12 cameras to take 12 pictures of
running horse
• Limitation of human vision system– persistence and fusion
Motion Picture Television Digital Video
ELE 488 F06
Motion Picture
• Perception of motion - persistence and fusion• 1877: Muybridge - 12 cameras to take 12 pictures of running horse • 1882: Marey - one camera to take 12 pictures per second• 1888: Dickson - motion picture camera
– Kenetoscope , single viewer projector (47 ft film, 25c for 5 shows) • 1895: Lumiere - projector/camera (hand-crank, 16 fr/sec, 20lb)• 1919: De Forest - optical sound on film• 1926 Warner B: “Don Juan” (John Barrymore, NY Philharmonic)• 1900 - : Film industry• 1940’s: Television• 1980’s: Digital Video
Recording event Re-live past moments Editing Creation of fictitious events / objects Manipulate perceived REALITY
ELE 488 F06
From Television to Digital Video
• Broadcast Television (analog)– movie at home - why invent new technology?– mass market– influence of movie on development
• Key Steps– convert pictures to electric signal– send electric signal – convert electric signal to picture
• Comparison with motion picture• High Definition Television - analog digital, compression
• Video telephone - analog predecessor• Video conference - travel cost, people cost• Cable (narrowcast), satellite, interactive, ...
ELE 488 F06
Key Steps in Broadcast Television
• Convert picture to electric signal – video camera– initially only at TV studios, cost not as important– recording media (tape), editing, …– special equipment to convert movie
• Send electric signal – follow radio broadcast, needs spectrum allocation
from FCC– VHF (Ch 2 – 13), UHF (Ch 14 & up)
• Convert electrical signal to picture– cathode ray tube offers economic solution– flat panel: LCD, LED, plasma panel– future
ELE 488 F06
Forming Picture on TV Tube (black-white)
How many lines?
ELE 488 F06
How Many TV Lines?
dot
dot
Cannot resolve if
distance > 2000 x separation
N = 500
ELE 488 F06
NTSC (National Television Systems Committee)
• 525 lines– 2 dots less than 1/2000 of distance from eye are not
separated (merge into one)– Assume view at distance 4 times the screen height. Dots
on screen less than (1/2000) x 4 x H = H/500 apart are not separated by eye. No need to have more than 500 lines
– NTSC set 525 lines (475 active)• Movies in 1940 has 4:3 aspect ratio (width to height)• 25 or more pictures per second to see continuous motion• 50 or more pictures per second to avoid flicker
– movies use 24 frames/sec, each shown twice• 30 frames/sec with 2:1 interlace (60 even-odd fields/sec)
ELE 488 F06
Television Tube
ELE 488 F06
2:1 Interlaced Scanning
even field odd field
ELE 488 F06
Bandwidth of Broadcast Television
• Without interlace (progressive scan), 60 frames/sec– 500 lines alternating black and white gives 250 full cycles– each horizontal line has 250 x 4/3 ~ 350 full cycles– 60 (frames/sec) x 500 (line) x 350 = 10,000,000 cycles/sec
or 10 MHz (video ONLY)
• With 2:1 interlace, 5 MHz for video
• FCC assigns 6 MHz per broadcast channel– real usable bandwidth is less, MUCH less– actual resolvable lines per vertical height ~250
• Color insertion - must compatible with B/W receiver– Change R-G-B to Y-Cb-Cr – Y is luminance (brightness), Cb and Cr are chrominances– B/W sets converts Y to picture, – Color sets converts Y-Cb-Cr to R-G-B, then display
ELE 488 F06
Digital Video
• What drives digital video?– Information technology:
• electronics, communication infrastructure, storage, functionality, …
– HDTV
• R-G-B component video– 640 x 480 (pixel) x 3 (color) x 8 (bits/color) x 30 = 221 Mb/sec
• Y-Cb-Cr with subsampled Cb and Cr– 640 x 480 (pixel) x 1.5 (color) x 8 (bits/color) x 30 = 110 Mb/sec