Review of Analog Video standards for Audio and video broadcast

1. Analog Video
Broadcast
Yossi Cohen
VDroid

2. Agenda
Introduction to Color Spaces
Connectors
Video Broadcast Standards
NTSC
PAL
Audio Standards
NICAM
BTSC
EIAJ
A2
Transmission Path
Reception Path

3. INTRO TO ANALOG TV
Color Spaces
Connectors
Broadcast Standards

4. Color Representation
The most simple way to represent G
color is by using RGB representation. B
The color space will look like:
This is usually the color space used
for:
Display output
Sometimes as camera input
For video compression & video R
transport other color spaces are used.
G
In those color spaces luminance is
separated from the color channel:
B
In the diagramed we see the YUV
space I U Y
Reasoning is the number and
sensitivity of the light sensing cells V
(rods) in the eye in comparison to color
sensing cells (cons) Q R

5. Color Models in Video
In Europe, video broadcast uses PAL or SECAM coding,
uses the YUV color model.
A matrix transform YIQ is used to transmit TV signals in
North America and Japan. (NTSC) This coding also
makes its way into VHS video tape coding in these
countries since video tape technologies also use YIQ.
Digital video uses a matrix transform called YCbCr that is
closely related to YUV.
Recently NV12 format has gained popularity

6. YUV Separation

7. YUV Color Model
YUV codes a luminance signal (for gamma-
corrected signals) equal to Y , the “luma".
Chrominance refers to the difference between a
color and a reference white at the same
luminance. (U and V)
The transform is:

8. YIQ Color Model
YIQ is used in NTSC color TV broadcasting.
Again, gray pixels generate zero (I;Q)
chrominance signal.
I and Q are a rotated version of U and V .
The transform is:

9. YUV / YIQ relationship
We can easily see that the
difference between YIQ &
YUV spaces is a 33 degree
offset of the IQ plane

10. Analog TV Connectors
Analog TV connectors have a tradeoff between
Number of Pins & wires
Quality of video
Using one wire to deliver luminance and color leads to
interferences between the luminance and color
components while using three wires or more just for the
video is not convenient.
Those problems are solved in new digital video connection
standards like:
DVI (obsolete)
HDMI 1.4

11. Composite Video
CVBS - Composite Video, Blanking, and Sync
Composite Video uses only ONE wire to transfer the mix
of:
Video color signals (chrominance)
Luminance signals
Since color and intensity are wrapped into the same
signal, some interference between the luminance and
chrominance signals is inevitable.

12. S-Video
S-Video uses two wires, one for luminance and another
for a composite chrominance signal.
This limits the crosstalk between the color information and
the gray-scale information.
Humans are able to differentiate spatial resolution in
grayscale images with a much higher acuity than for the
color part of color images.
As a result, we can reduce color information since we can
only see fairly large blobs of color, so it makes sense to
send less color detail.

13. Component Video
Component uses three separate video signals for R,G,B
planes.
Each color channel is sent as a separate video signal.
Most computer systems use Component Video, with
separate signals for R, G, and B signals.
Provides the best color reproduction since there is no
“crosstalk“ between the three channels.
Component video, requires more bandwidth and good
synchronization of the three components than
composite/S-Video .

14. ANALOG BROADCAST
STANDARDS

15. Broadcast Standard
The main Analog Broadcasting standards are:
NTSC
PAL
SECAM
They differ in:
Resolution
Frame Rate
Color scheme
Modulation methods
Channel BW
Carrier Distances

16. NTSC
• NTSC (National Television System Committee) TV standard
is mostly used in North America and Japan.
▫ 4:3 aspect ratio
▫ 525 scan lines
▫ 30 frames per second (fps)
• NTSC follows the interlaced scanning system, and each
frame is divided into two fields, with 262.5 lines/field.
• The horizontal sweep frequency is 525 X 29.97 = 15,734
lines/sec,
• Line swept cycle is 63.6u second.
• The horizontal retrace takes 10.9 u sec, this leaves 52.7 sec
for the active line signal during which image data is displayed

17. NTSC
NTSC video is an analog signal with no fixed horizontal
resolution. Therefore one must decide how many times to
sample the signal for display: each sample corresponds
to one pixel output.
A “pixel clock" is used to divide each horizontal line of
video into samples. The higher the frequency of the pixel
clock, the more samples per line there are.
Different video formats provide dierent numbers of
samples per line,

18. NTSC Color Modulation
NTSC uses the YIQ color model, and the technique of
quadrature modulation is employed to combine (the
spectrally overlapped part of) I (in-phase) and Q
(quadrature) signals into a single chroma signal C:
C = I cos(Fsct) + Qsin(Fsct)
This modulated chroma signal is also known as the color
subcarrier, whose magnitude is qI2 +Q2, and phase is
arctan(Q/I). The frequency of C is Fsc 3.58 MHz.
The NTSC composite signal is a further composition of the
luminance signal Y and the chroma signal as defined
below:
composite = Y +C = Y +I cos(Fsct) + Qsin(Fsct) (5:2)

19. PAL
PAL (Phase Alternating Line) is a TV standard widely
used in Western Europe, China, India, and many other
parts of the world.
4:3 Aspect Ratio
625 scan lines
25 frames/second
YUV Color space
8 MHz channel
5.5 MHz to Y
1.8 MHz each to U and V.
Color subcarrier frequency is fsc 4.43 MHz.

20. Analog Video Signal
B/W Sync Pulse
Luminance values
signal levels at 0-4.2MHz
Color Burst
Color Sync ~9-10 cycles
Color subcerrier at 3.85MHz
(NTSC)
Completing color values
Hue – Color Phase
Saturation – Color Amplitude

21. Audio and Video modulation
For NTSC
Total channel bandwidth is 6MHz
Luminance signal 0 - 4.2MHz
Color sub-carrier at 3.58MHz
Audio sub-carrier at 4.5MHz.

22. Video sub-standards
Standards defines:
Scan time
Resolution
signal
The sub-standards (B,GH, DK, M, N, L, I etc)
Modulation depth
Modulation type
Frequency map of the modulated channel

23. Audio Modulation Methods
Mono AM
BTSC / MTS
EIA-J
A2 / Zweikanalton
NICAM

24. Overview
Legacy TV only has monaural sound capabilities which
receives a single L+R channel
Later audio system delivered stereo capabilities while
supporting the legacy TVs:
Must provide the legacy mono channel
Add Stereo of L-R using new technique & Bandwidth

25. BTSC
BTSC includes:
Normal Mono is FM modulated over L+R
BTSC adds Stereo Channel by adding AM L-R
SAP – Secondary Audio Channel (like subtitles)
Optional Professional channel
Source: Video Demystified

26. EIAJ
Stereo Broadcast standard in Japan
Used in conjunction with NTSC-J, similar to BTSC
Uses FM instead of AM for the L-R Modulation
Differentiate between dual mono and single stereo using a
3.5FH subcarrier AM modulated (for 1/0)

27. A2
Instead of L+R and L-R transmission, A2 FM modulates two
separate L+R, R channels
This enables
Better L/R crosstalk performance
Transmission of two separate mono channels (second lang.)
Source: Video Demystified

28. NICAM
NICAM is used for Digital Audio broadcast.
NICAM uses an “A-Law Like” commanding algorithm.
NICAM Supports
One digital stereo sound channel.
Two completely different digital mono sound channels.
One digital mono sound channel and a 352 kbit/s data
channel.
One 704 kbit/s data channel.
NICAM scrambles bits to resemble white noise and
provides parity check

29. BTSC EIAJ A2 NICAM
Mono V V V V
Stereo V V V V
Dual Mono V V V
SAP V
Data V

30. Simplified Broadcast Path (Mono)
Audio IF Freq
Mono Audio FM
Modulator
Audio Video
41.25MHz
Video AM + HF
Conditioning
Modulator Modulator
Audio
video
666MHz
Video IF carrier freq Channel carrier freq
(30-40MHz) (~650MHz)

31. Broadcast Path
Conditioning
Back porch clamping
White clamping
LPF Filtering
IF Modulation
Fixed IF Frequency per standard
Carrier Modulation
Frequency changes according to channel

32. Signal Conditioning
FV Back Porch
Back Porch Clamping
clamping
-1.25MHz in NTSC
Reduce Channel BW
White Clamping
10%-90% of max signal
Prevents over modulation /
Buzzing
Chroma is added
3.58MHz in NTSC chroma
Low Pass Filtering
4.2MHZ in NTSC
chroma
BackLPF
Porch
clamping

33. Modulation
Video is AM modulated to IF
Audio Video
freq
45.75MHz in NTSC*
and mixed with modulated
Audio 41.25MHz 45.75MHz
41.25MHz in NTSC
The Signal is later modulated
to HF
Example of 666MHz
channel video Audio
664.25MHz 668.75MHZ
*For non-NTSC IF Frequency check backup slide

34. Simplified Reception Path
Audio
video
666MHz
SIF Audio I2S (Digital)
Display
Demodulator
Analog L,R (Analog)
Tuner Processor
CVBS Video
Digitizer Speakers
(HDMI)

35. Thank you!
More About me:
• Video Expert
Yossi Cohen
• Lectures on Video / Android /
VoIP
yossicohen19@gmail.com
+972-545-313092
• Android Native Developer