Fundamentals of Analogue and Digital

Broadcasting

Fundamentals of Analogue and Digital

Broadcasting

BSc. Media TechnologyBSc. Media TechnologyMay 2007May 2007

BSc. Media TechnologyBSc. Media TechnologyMay 2007May 2007

Q. Is it inevitable that all broadcasting will go digital?

• The radio spectrum is a finite resource• Society today wants more choice, more

TV channels, more phones, etc.• Digital broadcasting makes more efficient

use of the available radio frequency bandwidth

Q. Is it inevitable that all broadcasting will go digital?

• Analogue TV switch off planned to start in 2007 - 2012

• Digital distribution over the Internet is breaking down all the old models of broadcasting and traditional retail

Common Terms

Analogue

Digital

Bandwidth

Compression

Define the term Analogue:

• A continuous analogy of a sound or light wave transmitted as an electrical signal, which is an alternating voltage (A/C)

• Any audio or video equipment that has analogue signals going through it

• Old equipment!

A/C signalVolts

+

- Time

Waveforms:

Sine waves Complex waves

Analogue:

• Audio signals

• Video signals

• Problems: Distortion, not robust, large bandwidth signals

1011001101001001110010010101101110100100100010010010

10010DigitalDigital

Define the term Digital:

• Represent all signals or data with binary numbers, 0 or 1

• Turns audio and video signals into discrete values, e.g. snapshot measurements of the a/c voltage waveform at regular points in time

• Is this a new technology?

PCM - Pulse Code Modulation

Voltage

Time

5 4 3 2 1 0 1 2345

+

- + 2 = (10010011), + 4 = (10010100), - 1 = (01101100)

PCM - Pulse Code Modulation

Volume

Time

Advantages:

• Robust• Can be copied and cloned • No distortion

• Can take up less bandwidth than analogue when compressed

BandwidthBandwidth

Bandwidth

• This defines the maximum amount of information we can transmit through a given channel or connection

• Could be described as how much water you can get through a pipe

Bandwidth• In analogue broadcasting this is how

much of the radio spectrum is used by the TV channel or radio station

• In digital broadcasting: How many ‘bits per second’

Electro-magnetic Radio Spectrum

30 GHzEHF

3 GHzSHF

300MHzUHF

30MHzVHF

3 MHz300 KHz30 KHz

Radio Spectrum

150 -300 KHzLong Wave

AM

500 -1600 KHzMedium Wave

AM

6 -18MHzShort Wave

AM

88 -108 MHzFM

10.7 -12.7 GHz Satellite TV

217 -230 MHzDAB radio

470 -840 MHzTerrestrial TV

1800 MHzPCN

Mobile phones

900 MHzGSM

Mobile phones

2320 - 2345S Band

Digital Radio

1470 - 1490 MHzL Band

Digital Radio

Other used frequencies:Police, emergency services, military, navigation, CB radio, toys, microphones,WiFi, Bluetooth, etc.

Bandwidth Examplesshowing bits per second

Bandwidth Examplesshowing bits per second

Modem56 kbit

ADSL4 MbitCD audio

1.4 Mbit

DVD9.6 Mbit

HDTV &DV video25 Mbit

BluRay disc54 Mbit/sec

CompressionCompression

Compression

• Digital broadcasting would not be possible without data compression

• Compression also achieves the goal of efficient use of the airwaves

• We can now fit 6 - 8 digital TV channels into the same RF bandwidth as one old analogue TV channel

Codecs

• Short for code - decode• A mathematical algorithm describing how

to reduce the size of the data• Can be a Lossless or Lossy process• Can be built into a hardware device or

software running on a computer

Codec examples:

• Video: MPEG 1, MPEG 2, DivX, Windows Media video, MPEG 4 - H.264

• Audio: MP3, ATRAC, AAC, Windows Media audio, DTS, Dolby Digital AC3, Real Audio, Ogg Vorbis, MLP lossless

• Image: JPEG, JPEG2000, PNG, Gif, • Data: Zip, Stuffit

Compression Examplesstereo audio files

Compression Examplesstereo audio files

AAC-HE48 kbit/sec

Uncompressed CD audio1.4 Mbit/sec

MiniDisc282 Kbit/sec

MP3128 Kbit/sec

Summary:

• The global society is entering the digital information age

• All media production is becoming completely digital from start to finish

• For efficiency all broadcasting is going digital