Download - TVU Tech Episode 1 extra information
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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
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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
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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
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Common Terms
Analogue
Digital
Bandwidth
Compression
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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!
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A/C signalVolts
+
- Time
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Waveforms:
Sine waves Complex waves
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Analogue:
• Audio signals
• Video signals
• Problems: Distortion, not robust, large bandwidth signals
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1011001101001001110010010101101110100100100010010010
10010DigitalDigital
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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?
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PCM - Pulse Code Modulation
Voltage
Time
5 4 3 2 1 0 1 2345
+
- + 2 = (10010011), + 4 = (10010100), - 1 = (01101100)
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PCM - Pulse Code Modulation
Volume
Time
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Advantages:
• Robust• Can be copied and cloned • No distortion
• Can take up less bandwidth than analogue when compressed
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BandwidthBandwidth
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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
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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’
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Electro-magnetic Radio Spectrum
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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.
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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
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CompressionCompression
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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
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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
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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
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Compression Examplesstereo audio files
Compression Examplesstereo audio files
AAC-HE48 kbit/sec
Uncompressed CD audio1.4 Mbit/sec
MiniDisc282 Kbit/sec
MP3128 Kbit/sec
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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