Communication medium in modern tv

transcript

PRESENTED BY,

HARSH MEHTA

Communication mediums in

modern TV

1)Direct Broadcast Satellite TV(DBS -TV)

2)Internet Protocol Television(IP -TV)

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

• 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.

1)Direct Broadcast Satellite(DBS) television

DBS Television

• 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

• This is a large GEO DBS TV Satellite.

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.

• 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).

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 .

• 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.

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.

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.

Components involved in a DBS system

• 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.

Application

• Subscription-based TV

• Pay per-view (PPV)

• Digital video recorders (DVR)

• Interactive services

VIDEO COMPRESSION BASICS

(MPEG-2)

• 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

{Y, Cb,Cr}

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

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

• 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

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

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.

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)

Group of

pictures

• Intra coded frames (I-frames),

• Predictive coded frames (P-frames)

• Bi-directionally predictive coded frames (B-frames)

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

Raw Frame

IMPEG-2 Frames

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

Previous Future

References

Previous Future

INTERNET

PROTOCOL

TELEVISION

(IP-TV)

• 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.

What is IPTV?

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”.

• 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

Recommendations, Rating,

Guides etc.

User Experience

(VIDEO)

(VOICE)

TELECOM

(DATA)

Triple Play Service

ADSL Splitter

ADSL Modem

IPTV Set Top Box (STB)

Internet

Voice service

Landline

Triple play setup using ADSL modem and

splitter

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

• 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

Thank You