Digital Video Signal

7/27/2019 Digital Video Signal

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DigitalVideo

By

RAVINDRA NAITHANI

Assistant Engineer

Doordarshan Kendra Lucknow


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Analog video signal consists of three component video

signals, one Luminance signal Yand two color difference

signals CB, CR , derived from the primary colorsR,G,B

Component Video Signal

Y = 0.3R+0.59G+0.11BCB = 0.71(B-Y)

CR = 0.56(R-Y)

Matrix

R

G

B


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Component Video Signal

Y - Signal

CB - Signal

CR- Signal

sec52sec12

Active periodBlanking period


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Conversion of Analog Video to Digital Video Signal

( ITU-BT.R.601)

There are two main processes which convertanalog signal to digital signal

Sampling : Converting analog signal into discrete signal

Quantization : A process in which each discrete value is

represented or coded using a group of bits

(8 or 10 bits)

LPF Sample and

Hold

Quanitization

Analog Signal Digital Signal


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How to choose number of samples per second

1. Sampling frequency, fS must be greater than

or equal to Nyquist Frequency fN (=> 2fmax )

2. Sampling frequency must be the integermultiple of horizontal scanning frequency,

hf

3. Sampling Frequency is chosen to be 13.5 MHz which

is compatible to PAL and NTSC system and

computed from the following relation

PALhNTSChS fff ,, 864858

5.131562586415750858 Sf MHz


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Sampling Format

For every 2 2 Y pixels

4Cb & 4Cr pixels(No sub-sampling) 4:4:4 Format

4:4:4 Format

4:2:2 Format


2Cb & 2Cr pixels

(sub-sampling by 2:1

horizontally only)

Cb and Cr Pixels

Y Pixel


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Sampling Format Cont ..

4:1:1 Format


1Cb & 1Cr pixels(sub-sampling by 4:1

horizontally only)


1Cb & 1Cr pixels

(sub-sampling by 2:1both

horizontally and vertically)

4:2:0 Format


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sec33.53 sec66.10

Discrete Video Signal

Active period

Blanking period

720 Samples144

Samples


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Number of

samples in

PAL SDTV

Number ofsamples in

NTSC SDTV


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FORMAT RESOLUTION RAW BIT

RATE

REMARK

CCIR 601 720 ppl 576 Ipf 25 fps 149.3 Mbps Digital video

CIF 352 ppl 288 Ipf 30 fps 36.5 Mbps Digital video

QCIF 176 ppl 144 Ipf 30 fps 9.13 Mbps Digital video

SIF 360 ppl 288 Ipf 30 fps 37.3 Mbps Digital video

HDTV 1280 ppl 720 Ipf 59.94/60 fps

1920 ppl 1080 Ipf 29.97/30 fps

663.6 Mbps

1.3905 Gbps

Digital TV

NTSC 525 Ipf 29.97 fps Analog TV

PAL 625 Ipf 25 fps Analog TV

SECAM 625 Ipf 25 fps Analog TV

VGA 640 ppl 480 lines Computer

SVGA 1024 ppl 768 lines computer

List of source image / video formats


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Sampling of component in accordance of ITU-BT.R.601


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sec33.53 sec66.10

Quantization

Active period

Blanking period

1101001110110101

720 Samples144

Samples


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QuantizationQuantization Error/Noise

n

geVoltageRanAna

2

log

2

1


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Y

235 / 940

16 / 64

255 / 1023

0mv

Level Diagram

The video signal conforming to ITU BT R601, (Normally availableas a SDI signal), forms the input signal to an MPEG encoder.

700mv

0mv

240 / 960

16 / 64

255 / 1023

-350mv

350mv

128 / 512

Cb / Cr

0 / 0 0 / 0

1111 1111

1111 0000

0001 0000

0000 0000

Quantization

1000 0000

1110 1011

0001 0000


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SAV and EAV Code Words in the ITU-BR.R601

F = Field (0 = 1st field, 1 = 2nd field)

V = Vertical blanking (1 = vertical blanking interval)

H = SAV/EAV identification (0 = SAV, 1 = EAV)

P0, P1, P2, P3 = Protection bits (Hamming code)

S

AV

EAV

Cb Y Cr Y Cb

TRS-ID TRS-ID

SAV

EAV

Blanking orAncillary data

Blanking orAncillary data(Audio signal, or error protection information)

Active Line Pixel Data

TRS - ID : Timing reference sequence identificationSAV - Start of active videoEAV End of active video

Code pattern of SAV & EAV

11111111 (11) 00000000 (00) 00000000 (00) 1F V H P3 P2 P1 P0 (00)


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Sampling rate for analog video signal

Sampling Frequency for Y-signal 13.5 MHz

Sampling Frequency for CB-signal

Sampling Frequency for CR-signal

6.75 MHz

6.75 MHz

Bit rate for a digital video signal

with 8-bit quantization resolution13.5 *8=108 Mbps

6.75 *8=54 Mbps

6.75 *8=54 Mbps

216 MbpsTotal

Digital Video Data Rate

Sampling rate for analog video signal

Sampling Frequency for Y-signal 13.5 MHz

Sampling Frequency for CB-signal

Sampling Frequency for CR-signal

6.75 MHz

6.75 MHz

Bit rate for a digital video signal with

10-bit quantization resolution

13.5 *10=135 Mbps

6.75 *10= 67.5 Mbps

6.75 *10= 67.5 Mbps

270 MbpsTotal


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44.1 kHz

(32/44.1/48 kHz)

2*16*44.1=1.41 Mbps

Bit rate of digital audio signal with 16-

bit quantization resolutionSampling Frequency for

audio signal

Digital Audio Data Rate


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Serial Digital Interface (SDI)

Uncompressed digital Video signals have a data rate of 270 M.bits/s.

Digital video is distributed through SDI (Serial CCIR 601 Interface)

SDI uses waveform that is symmetrical about ground and has an

initial amplitude of 800 mVpp across 75 ohm load.

SDI signal can be fed through 75 ohm coaxial cable having BNC

connectors.

Unlike analog vide practice, serial digital receivers contain correct

termination that is permanently present and passive loop through isnot possible.

In permanent installations, no attempt should be made to drive more

than one load using T-pieces as this will result in signal reflections

that seriously compromise the data integrity.


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TRS-ID

Generator(Composite only)

10 bit

shift

register

8 or 10 bit

samples

Linedriver

75Coax. Equalizer

Scrambles

Descrambles

PLL

Shiftclock

360MHz

270MHz40Fx

PLL10

27MHz

36MHz

or 4 Fx Centre

Freq.

Adjust

30 bit

shift register

Latch

Sync

Pattern

detect

10

Out

Clock

Word

ClockBit

Clock

30

10

Regenerated

Clock


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THANK YOU

Documents

Digital Video Signal