communication medium in modern tv
DESCRIPTION
it is updated form of my last ppt .TRANSCRIPT
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PRESENTED BY,
HARSH MEHTA
Communication mediums in
modern TV
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1)Direct Broadcast Satellite TV(DBS -TV)
2)Internet Protocol Television(IP -TV)
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References:
• Timothy Pratt, Charles Bostian and Jeremy Allnut,
“Satellite Communications", John Wiley & Sons,Inc,Second Edition,2006.
• http://en.wikipedia.org/wiki/Direct-broadcast_satellite
• http://www.maplenet.net/~trowbridge/DBSintro.htm
• http://www.bretl.com/mpeghtml/MPEGindex.htm
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• directbroadcastsatellitetv-090723111626-phpapp02.slideshare
• HiSeasNet Training Courses, August 2009.doc
• iptv-121106124704-phpapp02.pptx.slideshare
• Tiberius Artzi, ”Direct Satellite Communication", US Patent
No.6553009,Issued on April 22,2003.
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1)Direct Broadcast Satellite(DBS) television
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DBS Television
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• DBS Satellite used to deliver TV programs to viewers all over the world. Ex
“Nile-Sat”
• The signals used by broadcast TV satellites are typically digitally compressed.
• The provider selects programs and broadcasts them to subscribers as a set
package.
Overview of the DBS
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• This is a large GEO DBS TV Satellite.
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Need of Multiple Access
• Satellites are usually built and employed for the common good of one or more regions.
• For this purpose, one of the several multiple access techniques, Mentioned are FDMA, TDMA and DAMA.
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FDMA
• Satellite frequency is already broken into bands, and is broken in to smaller channels in Frequency Division Multiple Access (FDMA).
• Overall bandwidth within a frequency band is increased due to frequency reuse.
• The number of sub-channels is limited by three factors:
1. Thermal noise (a signal will be effected by background noise).
2. Intermodulation noise ( a signal will cause noise).
3. Crosstalk (cause by excessive frequency reusing).
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FDMA can be performed in two ways:
• Fixed-assignment multiple access (FAMA): The sub-channel assignments are
of a fixed allotment. Ideal for broadcast satellite communication.
• Demand-assignment multiple access (DAMA): The sub-channel allotment
changes based on demand. Ideal for point to point communication .
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TDMA
• TDMA (Time Division Multiple Access) breaks a transmission into multiple time
slots, each one dedicated to a different transmitter.
• TDMA is increasingly becoming more widespread in satellite communication.
• TDMA uses the same techniques (FAMA and DAMA) as FDMA does.
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Advantages of TDMA over FDMA:
• Digital equipment used in time division multiplexing is increasingly becoming
cheaper.
• There are advantages in digital transmission techniques. Ex: error correction.
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Demand Assigned Multiple Access (DAMA)
• This technique is used when the link between the station and satellite is not a constant one.
• This helps assign bandwidth according to demand.
• This can be implemented on TDMA or as a combination with FDMA and TDMA.
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Components involved in a DBS system
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• Programming sources are simply the channels that provide programming for
broadcast. The provider doesn't create original programming itself; it pays
other companies for the right to broadcast their content via satellite.
• The broadcast center is the central hub of the system. At the broadcast
center, the TV provider receives signals from various programming sources
and beams a broadcast signal to satellites in geosynchronous orbit.
• The satellites receive the signals from the broadcast station and rebroadcast
them to Earth.
• The viewer's dish picks up the signal from the satellite and passes it on to the
receiver in the viewer's house.
• The receiver processes the signal and passes it on to a standard TV.
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Application
• Subscription-based TV
• Pay per-view (PPV)
• Digital video recorders (DVR)
• Interactive services
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VIDEO COMPRESSION BASICS
(MPEG-2)
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• A video comprises of a sequence of frames.
Frame 1 Frame 2 Frame 3 Frame 4
• A video, of the duration of 1 second, generated by a TV camera usually
contains 24 frames or 30 frames.
• Each pixel in a frame is represented by three attributes (each 8 bits long) –
One luminance attribute and two chrominance attributes. (i.e. YCbCr)
Luminance(Y): Describes the brightness of the pixel.
Chrominance(CbCr):Describes the color of the pixel.
Overview
Frame
{Y, Cb,Cr}
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Raw Frame GR B
• RGB color space contains mutual redundancies, so it requires large space for
storage and high bandwidth for transmission.
• Encoding RGB into YCbCr color space reduces the mutual redundancies
Raw Frame Cr y Cb
• converts block’s RGB data into YCbCr color space.
example:
YCbCr encoding
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Video Scheme
1. Interlaced Video Scanning
Types of video schemes used for transmission -
Bottom
Even numbered
rows in a frame.
Top Fields
Odd numbered rows
in a frame.
• The two successive fields (field 1 & field 2) are called a frame.
• Both the fields are sent one after another and display puts them back together
before displaying the full frame.
• Maximum frame rate is 60 frames/ second.
Field 1Field 2
• In this, a frame is divided into two separate fields – Top Fields and Bottom
fields.Frame
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• In this, complete frame is send to display.
• Bandwidth requirement is twice as compared to Interlaced video scanning.
• Quality is good as frames come in sync and image is much sharper.
• Maximum frame rate is 30 frames/ second.
2.Progressive Video Scanning
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1. MPEG-1 : It was the very first project of this group and published in 1993
• MPEG stands for Motion Picture Experts Group established in 1988 as a
working group within ISO/IEC that has defined standards for digital
compression of audio & video signals. Such as-
• MPEG-1 defines coding methods to compress the progressively scanned
video.
• Commonly used in CD-i and Video CD systems.
• It supports coding bit rate of 1.5 Mbit/s.
• Commonly used in broadcast format, such as – Standard Definition TV (SDT)
and High Definition TV (HDT).
• It supports coding bit rate of 3 - 15 Mbit/s for SDT and 15 – 20 Mbit/s for HDT.
2. MPEG-2: is an extension of mpeg-1 and published in 1995
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3. MPEG-4 : introduced in 1998 and still in development ..
• MPEG-4 defines object based coding methods for mixed media data and
provides new features, such as – 3D rendering, animation graphics, various
types of interactivity etc.
• Commonly used in web based streaming media, CD, videophone, etc. .
• It supports bit rate of few Kbit/s of Mbit/s.
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MPEG-2 Video CompressionMPEG-2 compresses a raw frame into three different kind of frames –
Raw Frame
I-Frame P-Frame B-Frame
• Compressed frames (I, P & B frames) are organized in a sequence to form Group of Pictures
(GOP).
I B P B P B P B I
(GOP 1)
B
Group of
pictures
• Intra coded frames (I-frames),
• Predictive coded frames (P-frames)
• Bi-directionally predictive coded frames (B-frames)
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1. I - Frame
2. P - Frame
• Compression is based on spatial redundancy(pixels) as well as on time based
redundancy(frame).
• P-frame can be predicted by referring I-frame or P-frame immediately preceding it.
• I-frame is a reference frame and can be used to predict the P-frame immediately following it.
• Compressed directly from a raw (uncompressed) frame.
• Compression is based in the current raw frame only and inability of human eye to detect certain
changes in the image.
Reference
P
Next
I
Reference
Previous
P
Next
P
Compressed
Raw Frame
IMPEG-2 Frames
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3. B - Frame
• Compression is similar to P-frame except that B-frame compression is done by referring
previous as well as following I-frame and or P frame.
Previous Future
References
B PI
Previous Future
References
BP I
References
Previous Future
BP P
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INTERNET
PROTOCOL
TELEVISION
(IP-TV)
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• IPTV stands for Internet Protocol Television.
• It is a digital television services that receives both TV or multimedia services
via Internet connection.
• IPTV will provide better quality of service than Internet streaming video.
• IPTV has the potential to offer an interactive, customized experience.
29
What is IPTV?
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Technology used in IP-TV
1.Broadband –the key element
• As Per The Telecom Regulatory Authority of India (TRAI):
“An always-on data connection that is able to support interactive services, and
has the capability of minimum download speed of 256 kbps”.
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• DSL Family Tree
1. Symmetric DSL
• Provide identical data rates upstream & downstream
2. Asymmetric DSL
• Provide relatively lower rates upstream but higher rates downstream
2. DSL – DIGITAL SUBSCRIBER LINES
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Recommendations, Rating,
Guides etc.
User Experience
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IP-TV
CABLE
(VIDEO)
MEDIA
TELCO
(VOICE)
TELECOM
ISP
(DATA)
IT
Triple Play Service
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ADSL Splitter
ADSL Modem
IPTV Set Top Box (STB)
Internet
Voice service
Video
Landline
Triple play setup using ADSL modem and
splitter
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Content Services in IP - TV Triple Play1. Broadcast type
• IPTV
• Pay TV
• Electronic Programme Guide (EPG)
• Live Streaming for VOD
• Progressive Downloads(Video, gaming, music downloads)
3. On Demand type
• Interactive VOD(video on demand)
• Client side Personal Video Recording
• Pay per View(PPV)
• Time Shifted TV
• Others ( Music Download, Music on Demand, TV based internet access, caller ID pop up)2. Interactive type
• Interactive TV
• Video Conferencing
• Interactive Online Network
Gaming
• Interactive E-Learning
4. Internet and Voice types
• VoIP
• Browsing on TV
• E-mail/SMS/MMS from TV
• Caller ID Popup35
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• Replace the PC for entertainment (Limit it for programming, documenting)
• Everything (e-mail reading, FB, answering calls) from TV remote controller.
Future of ip-tv
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Thank You