Digital TV ATV, Freeview, Freesat and all that…

1. Digital TVATV, Freeview, Freesat and all that… Noel Matthews G8GTZ

2. Agenda • Digital TV basics • Why compress? • Compression and modulation standards • HD and SD • Multiplexing • Services • SKY • FreeView • FreeSat • Digital ATV • Why and How

3. Why digital? • Analogue signals have been around since day 1 of broadcasting • The signals are very fragile and degrade very easily – poor “signal to noise ratio” • Scratchy records • Medium and long wave radio • FM radio hiss • Ghosting on the TV pictures • So we digitise it • Once the signal is digital we can modify and transmit it without degrading it • We can also copy and store it like computer data • CD were first real consumer digital products • But the problem is audio and pictures are very BIG

4. Digital video – how big? 1100101001010 Analogue 270 Mbit/s A to D converter PAL SDI

5. HD – an even bigger problem! 1100101001010 High Definition 1.3 Gbit/s A to D converter

6. Why compress video? • Serial Digital Interface (SDI) is the uncompressed digital studio standard • High quality loss-less digital video • 270 Mbit/sec is a lot of data! • approximately 33.3Mbytes per second • Not practical to transmit 270Mbit/s - except on optical fibre • Even worse with High Definition • Studio standard is 1.3 Gbit/s • Approximately 150M Bytes per second

7. Compression • In the broadcast world we compress using industry standard techniques • MPEG-2 • MPEG-4 • MPEG-2 Standard definition compresses video at 270Mbit/s down to 2Mbit/s • MPEG-4 High definition compresses HD video at 1.3Gbit/s to 8 Mbit/s • In less than 1 second • 99% reduction in bit rate but still better than VHS quality? • watch the background and grass! • And you get delay • Both standard use similar techniques • Interframe • Intraframe

8. Inter frame compression Macro block

9. Intra frame compression P P ref B non-ref B I non-ref B

10. Inter frame compression – 1 Source Frame A

11. Inter frame compression – 2 Source Frame A

12. Inter frame compression – 3 Source Frame A

13. Inter frame compression – 4 Source Frame A

14. MPEG-2 and MPEG-4 • Standards are crucial to the success of the broadcasting industry • Ensures interoperability between the transmission head end and the set top box • 2 main standards affect what we do • Motion Pictures Expert Group (MPEG) • Video compression • Digital video broadcasting (DVB) • Transmission standards • MPEG-2 has been the major standard for the last 15 years • 100 million STBs! • But we needed something better • MPEG-4 is a completely new algorithm • 50% more efficient • Standard Definition used for “green field” • DTV and IPTV • High Definition used everywhere • SKY • FreeSat

15. Advanced Encoding Future 2005 1997 2000 2004 1994 1995 1996 1998 1999 2001 2002 2003 MPEG-2 - improvements Bit-rate for Broadcast First Broadcast MPEG-2 Encoder Quality Television* 8 7 TM Reflex Statistical Multiplexer Enhancements 6 Bit Rate (Mbits per second) Enhanced Motion 5 Estimation 4 TTV Noise Reduction 3 Advanced Pre- MPEG-2 Future processing 2 1 Year

16. How good is MPEG-4?

17. Typical System Architecture

18. Don’t forget the audio! • As many channels as you like • it’s only bits • Mono, dual Mono • Stereo, joint Stereo • Multiple languages • 5 Channel surround sound • Dolby & DTS • Sample rates from 32 – 256 Kbit/s

19. Not just pictures - EPG and CA • The EPG is the user interface • Transmitted at same time as TV and radio services • Contains program info plus forward looking data • Also available as XML files on the internet • Condition Access prevents illegal viewing of pay TV channels • None encrypted channels are known as Free To Air (FTA)

20. Putting it all together - Multiplexing • Alongside pictures we have stereo audio, conditional access EPG data etc • Can even multiplex SD & HD together • Also many programs are combined in to one big bit stream • Sky = 10 channels + • Freeview = 6 channels • to get many channels in a single radio channel • Can multiplex SD & HD together • Even greater gains using statistical multiplexing! • But that’s another story • SPTS used by IPTV and amateurs

21. Modulators • Now we have a data stream (or multiplex) containing all our programs we transmit it • Using DVB standards • Over terrestrial channels • Using DVB-T (OFDM) • From transmitter towers • Over satellite • Using DVB-S (QPSK, 8PSK or DVB-S2) • Over cable • Using DVB-C = QAM • Modulator at edge for VoD – hence “edge QAM” • Over IPTV • No standard adopted! • Not web TV

22. Multi vs single carrier • All use error correction • Transmitted rate is not useable video rate • Single carrier QPSK • Bandwidth varies with Bit rate • Gives DX mode • Half the symbol rate = 3dB • Multi-carrier OFDM • Fixed bandwidth • Freeview = PAL replacement = 8 MHz • Uses “guard interval” to protect against frequency selective fading

23. Multi-carrier vs single QPSK O F D M

24. OFDM on air

25. QPSK on air

26. Typical System

27. Hampshire technology = 2,000+ customers

28. Agenda • Digital TV basics • Why compress? • Compression and modulation standards • HD and SD • Multiplexing • Services • SKY • FreeView • FreeSat • Digital ATV • Why and How

29. The UK market • Probably the most advanced market in the world • 22million TV households • 5 major platforms providing a variety of services over different delivery systems: • Sky = DTH pay TV satellite • Freeview = Terrestrial • Virgin = cable • FreeSat = Free to air satellite • BTVision = “Hybrid IPTV”

30. FreeView • Digital terrestrial service • Transmitted from TV masts around the country • Will become the main service after Analogue Switch Off in 2012 • Government funded through Free To View Ltd • Very tight on bandwidth – a channel costs £12m pa • 6 frequencies transmitted from each station • 6 services per channel • Approximately 30 TV channels and 30 radio stations • 4 pay to view channels • Currently 16m STBs (not homes!) • Available via a STB or integrated TV • Currently uses MPEG2 Standard Definition and DVB-T • Experiments with MPEG4 HD and DVB-T2 • Large amount of TTV equipment – and growing;-0)

31. SKY • Satellite based pay to view service • 8.5m subs • Virtually unlimited bandwidth • 300 programs approximately • Mixture of pay to view, FTA and national TV services • SKY services are encrypted • Need a Sky Box to view • SKY boxes can view free to air • The SKY EPG joins it all up • Most channels are MPEG-2 Standard definition • 20+ MPEG-4 High definition channels • All TANDBERG TV technology ;-0)

32. BT Vision – 300k subs • BTVision is a “hybrid” service • Uses FreeView to deliver TV - free • Uses phone line to deliver on demand assets • Hybrid PVR set top box with hard disk • Is NOT a true IPTV service! • Why Hybrid? • Needed to have a TV offering to stop customers leaving • BT network cannot support live TV • Movies are trickle fed to the STB • Uses Microsoft MSTV system • Great way to get a free Freeview PVR and powerline adaptors!

33. Virgin Media – 3m subs • Consolidation of all UK cable companies (except IOW!) • Only available where the streets have been dug up! • Very controlled environment so high bit rates • 36 Mbit/s & 54 Mbit/s • MPEG2 SD and HD • Plenty of bandwidth • USP is a 2 way system with return path • High speed internet • VoD services

34. FreeSat – 100k subs • The BIG secret! • Is just an EPG!! • Uses same transmissions as SKY at 28 degrees east • FreeSat boxes have a new EPG to only list FTA channels • Will have MPEG2 SD and MPEG4 HD • Note ITV HD is encrypted at moment • Issues with SKY contract! • Designed to compliment FreeView • Gives 99.5% coverage • But could end up being the winner!

35. Internet or Web TV • Internet or web TV is watching video from a website • Not IPTV as quality is not guaranteed • 28% of Europeans currently watch short or full-length videos on-line • an increase of 150% since 2006.  • Biggest sites are “catch up TV” • BBC iPlayer, Ch4 on demand • BBC iPlayer is the outstanding success • 271m plays in 2008 • 41m plays in December • AND BATC.TV!

36. Agenda • Digital TV basics • Why compress? • Compression and modulation standards • HD and SD • Multiplexing • Services • SKY • FreeView • FreeSat • Digital ATV • Why and How

37. ATV • Most ATV is on 23cms or 1300MHz • Analogue FM • GB3IV = 1316 output • Some DATV activity using QPSK • 2 or 4 MHz bandwidth • Cheap receivers! • Expensive transmitters • Got gain but you can’t tweak!

38. Analogue P2

39. Digital P5

40. Pre-amp FM rxr Digital rxr In the shack Switch/ splitter/ amp

41. QPSK modulator MPEG encoder SSB transverter DATV transmit Power Amp

42. WWW.BATC.TV • Internet web site with loads of video clips! • The easy way to get on ATV • Most UK repeaters stream in real time • Including GB3IV from the IOW • Video & repeater audio plus 144.750 MHz talkback • GB3IW streamed on IV site • Real time chat room for talkback

44. Summary • It’s a digital world • Every picture you watch has been digitzed at some point! • Pictures are not better • You start at 270 Mbit/s and watch 2 Mbit/s! • Digital will happen • Digital has gain over analogue • Spectrally efficient • We should start to experiment now • Digital can save 70cms ATV • Have a look at www.batc.tv