Post on 25-Dec-2015
transcript
Video Media
Department of Computer EducationKMUTNB
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Video MediaM
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iaVideo features in a range
of Multimedia application
• Entertainment – Broadcast television and VCR/DVD
recordings
• Interpersonal– Video telephony and videoconferencing
• Interactive– Windows containing short video clips
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Video MediaM
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iaBroadcast Television
• 525 Lines– NTSC American standard– 60 Fields / second– 30 Frames / second
• 625 Lines– PAL European standard /CCIR/SECAM– 50 Fields / second– 25 Frames / second
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Video MediaM
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iaScanning illustrated
Time
Volt
ag
e 1 2 3 4 5 6
123456
720 Sample
720 pixel
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Video MediaM
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iaType of Scanning
• Progressive = every scan line done in turn.
• Interlaced = every other scan line done.– Creates two fields: odd field and even field.– NTSC: 262.5 lines per field at 60 fields per
sec.– PAL: 312.5 lines per field at 50 fields per
sec.
• Fields are separated in time.
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Video MediaM
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iaComputer & TV
1 TV Frame = 2 Field
interlaced scan
1 Computer Frame
Progressive scan
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Video MediaM
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iaComputer & TV
Television
Computer1 Frame
1 Frame
1 2 3 4 5 6 7 .. ….. 625
……. …..
……. …..
1 3 5 7 .. ….. 625 2 4 6 8 ……
624
…….
312.5 Even Field
312.5 Odd Field
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Video MediaM
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iaVideo capture with both
fieldComputer 1
1 2
3 4
5 6
7 .. …
.. 625
……
. …..
……
. …..
1 3
5 7
.. …..
625
2 4
6 8
……
624
……
.
312
.5
Even
Field
312
.5
Odd
Field
Television Computer 2
1 2
3 4
5 6
7 .. …
.. 624
……
. …..
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Video MediaM
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iaVideo capture with one
fieldComputer 1
1 2
3 4
5 6
7 .. ..3
12
….
……
. …..
1 3
5 7
.. …..
625
2 4
6 8
……
624
……
.
312
.5
Even
Field
312
.5
Odd
Field
Television
Discard
1MPEG ( VCD)
From Interlaced to Progressive system discard resolution in half
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Video MediaM
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iaScanning Sequence in TV
Interlaced scanning principles
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Video MediaM
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iaScanning Sequence in TV
525-line systems : 262.5 each field, 240 visible625-line systems : 312.5 each field, 288 visible
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Safe Frame
From Camera View Finder
To TV
To Digital File
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Video MediaM
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iaBroadcast Television
• Video resolution and quality
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Video MediaM
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ia3 Main Properties of a
Color
• Hue: The actual color of the source, each color has a different frequency/wavelength and eye determines the color from this.
• Saturation: The strength of vividness of the color, a pastel color has a lower level of saturation than a color such as red.
• Brightness : The amount of energy that stimulates the eye and varies on a gray scale from black (lowest) Through to white(highest)
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Video MediaM
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iaLuminance & Chrominance
• Luminance : is used to refer to the brightness of a source, and the hue and saturation
• Chrominance: is used to refer to the color characteristics.
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Video MediaM
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iaTV Color Signals
Component Signal
Luminance
Chr omi nance
Traditional monochrome TV
White --> Black
Magnitude of the 3 electrical signals that energize the R,G,B Phosphors
0.299R + 0.587G + 0.114B
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Video MediaM
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iaComposite Video Signals
Ys = 0.299 Rs + 0.587 Gs + 0.114 BsCr = Rs - YsCb = Bs - Ys
Ys is amplitude of luminance signalRs, Gs, Bs is magnitude of 3 color
component signals
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Video MediaM
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iaComposite Video Signals
R
G
B
+
-
-Cr
Ys
Cb
-
Rs
Gs
Bs
monochrome
+
+Composite Video Signal
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Video MediaM
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iaChrominance components
From Ys, Cr, CbPAL : Y = 0.299 R + 0.587 G + 0.114 B
U = 0.493 (B - Y) V = 0.877 (R - Y)
NTSC : Y = 0.299 R + 0.587 G + 0.114 B
I = 0.74 (R-Y) - 0.27(B-Y) Q = 0.48 (R-Y) + 0.41(B-Y)
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Video MediaM
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iaSignal bandwidth
Baseband spectrum of color television signals in NTSC system 42NTSC : Y = . MHz
2 2 2 2=2 2 2 2 2= 1
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Video MediaM
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iaSignal bandwidth
Baseband spectrum of color television signals in PAL system 2 2 2: =5 . 5
2 2 2 2= 3 2 2 2 2=3
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Multimedia SummaryM
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iaDigital Video Frames
• Almost always progressive• 3 planes of pixel values (Y, U, and
V)• Pixel depth• Geometry of each plane: width x
height– Chrominance is generally
subsampled.
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Video MediaM
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iaDigital video
• The visual perception of the eye have less sensitive for color than luminance
• This means that 2 chrominance signals can tolerate a reduced resolution relative to that used for the luminance signal
• Saving in terms of resulting bit rate and transmission bandwidth
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Video MediaM
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iaDigital video standard
• International Telecommunications Union Radiocommunications Branch (ITU-R)
• Formerly known as the Consultative Committee for International Radiocommunications (CCIR)
Recommendation CCIR-601
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Video MediaM
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iaCCIR-601
• Standard established for digitizing NTSC and PAL signals
DigitalComponent
AnalogCounterpart
CCIR-601Recommendation
Height Lines NTSC: 480PAL: 576
Width Continuousvoltage changesalong scan line.
Sample at 13.5 MHzResults in 702 pixelsRecommended 720
Pixel depth Voltage range. Gamma-corrected8-bit sample.
Chrominancesubsampling
Bandwidthdifferences
4:2:2, 4:2:0, 4:1:1
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1,4
1,3
1,2
Video MediaM
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iaVideo Color Storing
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
The visual perception of the eye have less sensitive for color than luminance
From Source Storing method
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1,4
1,3
1,2
Video MediaM
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iaVideo Color Playback
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
1,1
1,1
1,1
1,1 3,
13,1
3,1
3,1
3,2
3,2
3,3
3,3
3,4
3,4
Cr,Cb Cr,Cb
Playback process
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Video MediaM
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iaVideo Digitization Formats
4:2:2 means 2:1 horizontal downsampling, no vertical downsampling. (Think 4 Y samples for every 2 Cb and 2 Cr samples in a
scanline.) 4:1:1 ought to mean 4:1 horizontal downsampling,
no vertical. (Think 4 Y samples for every 1 Cb and 1 Cr samples in a
scanline.) It is often misused to mean the same as 4:2:0 .
4:2:0 means 2:1 horizontal and 2:1 vertical downsampling. (Think 4 Y samples for every Cb and Cr samples in a scanline.)
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Video MediaM
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ia4:2:2
• Use in television Studio• For every 4 luminance samples,
take 2 chrominance samples from odd lines and 2 from even lines.
• Chrom. planes just as tall, half as wide.
• JPEG does this.
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Video MediaM
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ia4:2:2
Sample positions with 4:2:2 digitization format
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Video MediaM
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ia4:2:2
Sample positions with 4:2:2 digitization format
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
From Source Storing method
Every 4 pixel
Keep 2 odd
Keep 2 even
Storage size Y+Cr+Cb Storage size Y+0.5Cr+0.5Cb
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ia4:2:0
• Used in Digital Video broadcast application
• 2 chrominance samples for every 4 luminance samples, odd lines only.
• Chrominance halved in both directions.
• MPEG generally does this.
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Video MediaM
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ia4:2:0
Sample positions with 4:2:0 digitization format
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Video MediaM
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ia4:2:0
Sample positions with 4:2:0 digitization format
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
From Source Storing method
Every 4 pixel
Keep 2 odd
Keep 0 even
Storage size Y+Cr+Cb Storage size Y+0.25Cr+0.25Cb
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Video MediaM
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ia4:2:0
4:2:0 playback process
1,2
YCr
Cb
1,1 2,
2
2,1
1,2
YCr
Cb
1,1
2,2
2,1Play
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Video MediaM
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ia4:2:0
• To avoid flicker effect with the chrominance signal– the receiver uses the same chrominance value
from the sampled lines for the misslines
• Large-screen flicker effects are often reduced by– storing the incoming digitized signals of each
field in a memory buffer– Double the normal rate 100/120 Hz then used
with the stored set of signals used for the 2 field
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Video MediaM
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iaHDTV
• High-Definition Television• Older 4/3 aspect ratio 1440 x 1152 pixels• newer 16/9 aspect ratio 1920 x 1152
pixels• 1080 visible lines per frame• 4:2:2 digitization for studio application
– Frame rate 50/60 Hz
• 4:2:0 digitization for broadcast application– Frame rate 25/30 Hz
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Video MediaM
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iaSIF
• Source Intermediate Format• Used in Video Cassette Recorders (VCR)• Used Half spatial resolution in both
horizontal and vertical in 4:2:0 format• Frame rate 30 Hz for 525 line, 25 Hz for
625 line• Progressive (non interlaced) scanning• The receiver estimated by interpolating
between each pair of value missing line
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Video MediaM
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iaSIF and CIF
Sample positions for SIF and CIF
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Video MediaM
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iaSIF and CIF
Sample positions with 4:2:0 digitization format
1,4
1,3
1,2
YCr
Cb
1,1
2,4
2,3
2,2
2,1
3,4
3,3
3,2
3,1
4,4
4,3
4,2
4,1
1,3
Y1,1
3,3
3,1
From Source Storing method
Storage size Y+Cr+CbStorage size 0.25Y+0.0625Cr+0.0625Cb
CrCb
2,2
2,2
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Video MediaM
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iaSIF and CIF
Sample positions with 4:2:0 digitization format
1,3
1,3
1,1
Y Cr All 2 ,2
Cb All 2 ,2
1,1
1,3
1,3
1,1
1,1
3,3
3,3
3,1
3,1
3,3
3,3
3,1
3,1
Playback
1,3
Y1,1
3,3
3,1
Storing method
CrCb
2,2
2,2
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Video MediaM
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iaWhen Capture from Video
Tape
Sample positions with 4:2:0 digitization format
1,3
Y1,1
3,3
3,1
From Video Tapeor Home use Quality Signal
2,2
2,2 1,
3
YCr
Cb
1,1 3,
3
3,1
Capture to Computer
360x288360x288
VideoTape
VideoClip
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Video MediaM
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iaCIF
• Common Intermediate Format• Defined for use in Videoconferencing
applications• Typical bit rate used is a single 64 kbps ISDN
channel• Can multiple channel for high bit rate
4CIF: Y= 720 x 576Cb = Cr = 360 x 288
16CIF: Y= 1440 x 1152Cb = Cr = 720 x 576
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Video MediaM
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iaCIF
CIF 6 4 kbpsCIF 6 4 kbps
360x288
360x288
CIF720x576
720x576
CIF
CIFCIF CIF CIF
CIFCIF
256 kbps
256 kbps
6 4 kbps
6 4 kbps
In Videoconference Application
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Video MediaM
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iaCommon Digital Video
Sizes
• CCIR-601 720x480 4:2:2, 4:2:0• SIF 360x240 4:2:0• CIF 360x288 4:2:0• 4:3 HDTV 1440x1152 4:2:2, 4:2:0• 9:16 HDTV 1920x1152 4:2:2,
4:2:0• 4CIF, 16CIF, QCIF
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Video MediaM
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iaPC video digitization
formats
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Video MediaM
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iaMultimedia Communication
Standards
• H.320 Video Teleconferencing Standard– Visual Telephone System over N-ISDN
• H.324– low bit rate multimedia communication terminal
for PSTN and Mobile Radio
• H.321, H.310 – high resolution broadband audiovisual
communication systems via B-ISDN
• H.322, H.323– narrowband visual telephone services on LAN
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Video MediaM
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iaReferrence
• Multimedia communication Application, Networks, protocols and standards; fred halsall. Chapter 2 Multimedia information representation page 96-113; ISBN 0201398184
• http://www.sce.carleton.ca/courses/96502• http://www.crs4.it/~luigi/MPEG/ccir601.html• http://www.broadcastengineering.com/archives/
0198/199801be15.html• http://www.cs.unc.edu/~kmp/classes/sp01/comp249