1. University of Canberra Advanced Communications Topics
Television Broadcasting into the Digital Era
Lecture 2
Digital Video
Formats, Standards
and Sampling
by: Neil Pickford 1

2. Standard Definition Television SDTV
The current television display system
4:3 aspect ratio picture, interlace scan
Australia/Europe
625 lines pixels x 576 lines displayed
50 frames/sec 25 pictures/sec
pixels total
USA/Japan
525 lines pixels x 480 lines displayed
60 frames/sec 30 pictures/sec
pixels total
SDTV - The television system we have at the moment

3. Enhanced Definition Television EDTV
Intermediate step to HDTV
Doubled scan rate - reduce flicker
Double lines on picture - calculated
Image processing - ghost cancelling
Wider aspect ratio - 16:9
Multi-channel sound
Next Step up towards HDTV
Line doubling is done by interpolating the lines inbetween the transmitted lines.
Ghost Cancelling was one of the last advances in analog television technology to be incorporated in Australia

4. High Definition Television - HDTV
Not exactly defined - number of systems
System with a higher picture resolution
Greater than 1000 lines resolution
Picture with less artefacts or distortions
Bigger picture to give a viewing experience
Wider aspect ratio to use peripheral vision
Progressive instead of interlaced pictures
HDTV
Many people are talking about it but it is not exactly defined.
Wider aspect ratio so it starts to engrosse your peripheral vision, unlike normal TV which primarily occupies the central vision.

5. HDTV Have We Heard This Before?
The first TV system had just 32 lines
When the 405 line system was introduced it was called HDTV!
When 625 line black & white came along it was called HDTV!
When the PAL colour system was introduced it was called HDTV by some people.
Now we have line systems and digital television - guess what? Its called HDTV!
HDTV - This term has been used over and over.
Some people are saying we are not going to make any money out of HDTV, however in the press clipping of 1930s & 1950s the same type of people were saying the same things about the HDTV improvements then. Just talk to the TV companies and see if they are making any money?

6. All Current Generation PCs use Progressive
Do You Use A PC?
All Current Generation PCs use Progressive
Scan and display
Pictures which match
or exceed HDTV
resolutions although the pixel pitch, aspect ratio and colorimetry are not correct.
HDTV
Some PC monitors have RGB bandwidths exceeding 120 MHz. HDTV only requires 30 MHz.

7. Digital Television Why digital?
To Overcome Limitations of Analog Television
Noise free pictures
Higher resolution images Widescreen / HDTV
No Ghosting
Multi-channel, Enhanced Sound Services
Other Data services.
The average domestic TV in Australia has all sorts of distortions. Digital TV will remove those distortions. Just like a CD, you never hear a scratched CD. It’s either perfect or it’s nothing.

8. Enabling Technologies
Source digitisation (Rec 601 digital studio)
Compression technology (MPEG, AC-3)
Data multiplexing (MPEG)
Display technology (large wide screens)
Transmission technology (modulation)
Production
Digital TV has Key Technologies that make it possible. Most production within the current TV stations already happens in the digital domain using standards such as Rec 601 digital video. It only becomes analog when it is transmitted over the air to the viewer.
Display technology has not reached the level needed for HDTV to be fully implementable at present.

9. Sampling
Digital video requires sampling of the Analog image information.
Highest quality achieved when sampling Component video signals.
For SDTV a basic luminance sampling frequency of 13.5 MHz has been adopted.
Various methods exist to sample the complete colour image information
4:2:2 4:4:4
4:1:1 4:2:0

10. YUV Sampling Points 13.5 MHz
YUV YUV
YUV Sampling Points 13.5 MHz
4:4:4
YUV Y Only
4:2:2

11. YUV Sampling Points 13.5 MHz
4:1:1 & 4:2:0 MPEG-1 Sampling
YUV Y Only Y Only Y Only
YUV Sampling Points 13.5 MHz
4:1:1
Y V Y
Y U Y
JPEG/JFIF H.261 MPEG-1
4:2:0

12. YUV Sampling Points 13.5 MHz
4:1:1 & 4:2:0 MPEG-2 Sampling
YUV Y Only Y Only Y Only
YUV Sampling Points 13.5 MHz
4:1:1
YV Y Only
YU Y Only
Co-sited Sampling MPEG-2
4:2:0

13. Rec BT-601/656 Digital Standard for Component Video
27 MHz stream of 8 / 10 bit 4:2:2 Samples
8 bit range 219 levels black to white (16-235)
Sync/Blanking replaced by SAV & EAV signals
Ancilliary data can be sent during Blanking
128 16
235
0 & 255 Y V U

14. Parallel BT-656 1st Rec 656 connection format used.
Uses 110 Ohm twisted pairs for data and clock
ECL level 27 MHz
Width: 10 bits NRZ data + 1 clock pair
Uses standard DB-25 Female on Equipment
All cables are DB-25 Male to Male pin for pin
All cables have overall shield to prevent EMI
Max length without a DA 50 m, with EQ 200 m

15. SDI - Serial BT-656 Serial Data Interface - Current version of 656
Uses standard 75 Ohm video coax Cabling
1300 nm Optical fibre interface also defined
270 Mb/s Serial data stream of 10 bit data
X9+X4+1 scrambling used for data protection
Encoding polarity free NRZI 800 mV pk-pk
4 channel Audio can be encoded into ancillary data areas during the blanking period

16. Video Formats - SDTV - 50 Hz
Here are some of the SDTV video formats, with the relevant number of pixels and bitrate.
All these formats are Interlaced

17. Video Formats - HDTV - 50 Hz
HDTV formats with pixels and bitrate.
Yellow are interlaced formats
White are progressive formats
Green can support both formats

18. HD Video Formats
1152
1440
1,658,880
1080
1920
2,073,600
576
720
414,720
720
1280
921,600
480
345,600
1,552,200

19. Common Image Format CIF
1920 pixels x 1080 lines is now being promoted as the world CIF.
All HDTV systems will need to support this image format and then allow conversion to any other display formats that are supported by the equipment.
In Australia we have adopted the CIF for our HDTV production format. The Recommended Video format is 1920 x 1080 Interlaced at 50 Hz with a total line count of 1125 lines.
Finally the International community have got together and defined a Common Image Format (CIF) for HDTV type production. This means that world wide people can produce material in the same HD format allowing easier interchange without standards conversion. All the future HDTV systems will support this format even if they are working with lower level display devices, they will be required to be able to up or down convert to the CIF.

20. HDTV Parameters - AS 4599
HDTV Defined as a MPEG-2 stream which is compliant with encoding.
HDTV sample rate:
Less than samples per second
Greater than samples per second
Systems with less than samples per second are defined as SDTV

21. Chromaticity
SDTV needs compatibility with legacy displays, so default SDTV chromaticity in DVB is:
same as PAL for 25Hz
same as NTSC for 30Hz
HDTV has unified world-wide chromaticity and no legacy displays
default is BT.709 for both 25Hz and 30Hz
simulcast allows mixture of legacy chromaticity for SDTV and BT.709 for HDTV
Often neglected until you get it wrong, then it becomes very visible.

22. Colour Difference Signals
BT-709 Colorimetry
HDTV uses a different colour space to SDTV
HDTV display Phosphors not same as SDTV
BT-709 defines the parameter values for HDTV
HDTV has a slightly different colour equation
Y = R G B
U = (B - Y)
V = (R - Y)
Colour Difference Signals