Video Media

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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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


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


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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Video MediaM

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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


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Video MediaM

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ia4:2:0


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


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


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


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


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


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

Video Media

Documents

Transcript of Video Media