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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
For every 2 2 Y pixels
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
For every 4 1 Y pixels
1Cb & 1Cr pixels(sub-sampling by 4:1
horizontally only)
For every 2 2 Y pixels
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