Copyright © Steven Morris 2005 All Rights Reserved Downloaded from An introduction to DTV receiver technology Steve Morris

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from What does a DTV receiver do? Receives digital TV broadcasts from a cable, satellite or terrestrial network Decodes them Outputs them to a television or other display device –This display device is usually a television May do other things –E.g. execute applications included with the broadcast

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Types of digital TV receiver Set-top box (STB) –The most common type –Varies in functionality and features from very basic to very advanced –May be integrated with other types of device E.g. a DVD player or PVR system Integrated Digital TV (IDTV) –Receiver is built into a TV set –Can receive digital or analog broadcasts with no extra hardware PC with digital tuner card –Similar to analog TV tuners, except it decodes digital TV signals

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Block diagram of a typical receiver TunerFront-end Smart card / CA Module MPEG-2 decoder CPU Middleware SDRAM Flash memory Graphics processor Descrambler MPEG-2 demultiplexer

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from The Front End The part of the receiver that actually receives the analog signal and converts it into a stream of bits –Two main components, the tuner and the front end –These may be integrated into a single package –Usually specific to cable, satellite or terrestrial networks –Some may support both analog and digital signals The tuner –Receives a signal on the frequency specified by the rest of the STB –Demodulates the signal –Turns the analog signal into a digital bitstream The front-end –Performs first level of error correction –Removes the first level of packetization in the stream –Outputs an MPEG-2 transport stream in digital format

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from The Demultiplexer Takes an MPEG-2 transport stream and locates those elements that the STB is interested in –All elements of the current channel Audio and video streams Broadcast data streams Service information –Some service information for the network as a whole Passes these streams on to other parts of the system –Service information and data streams to the CPU (if it is interested) –Audio and video to the MPEG decoder Other data from the transport stream is thrown away –But demultiplexer may include section filtering capability to filter other MPEG-2 sections as requested by applications

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from The MPEG Decoder Decodes audio and video streams and displays them on the screen May include support for graphical overlays –Cursor, graphics –Some receivers support up to five graphics planes Background, video, two graphics planes, cursor May include support for scaling, clipping and repositioning video –But this may be limited Typically combined with the graphics processor –Makes it easier to integrate different elements of the display

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from The CPU Handles all of the other tasks in the system –Decoding and handling service information –Decoding broadcast data streams –User interaction –Running built-in or downloaded applications Often integrated with the MPEG-2 decoder and other components Typical CPUs –STMicroelectronics 551x family –NEC EMMA2 –ATI Xilleon –Broadcom BCM3560

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Conditional access (CA) Anti-piracy system for pay-TV –Decrypts some or all of the data Depending what was encrypted by the network operator –Usually based around some kind of physical token Smart card or similar device Only that token will work with that receiver Each STB usually has one CA system integrated –This is enough for most pay-TV systems –The box is tied with the subscription, so only used on one network and one CA system Most common CA vendors: –Canal + (MediaGuard) –Philips (Cryptoworks) –Irdeto (IrdetoAccess) –General Instrument (DigiCypher II) –NDS (VideoGuard) –Nagravision-Kudelski (Nagravision) –Conax (Conax) –Motorola –France Telecom (Viacess)

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Conditional Access (CA) Some CA systems require special hardware support –e.g. NDS –Usually features built into the CPU –Most systems will use a standard Smart Card slot Some receivers will use two, one for CA and one for banking card, etc. Some network operators are now using pure software CA systems –No need for extra hardware module –Makes it quicker to roll out new encryption when the old one is cracked –May still use smart cards for authentication CA systems may do more than just encryption –Pair a smart card to a single receiver Smart card can not be moved to other receivers –Provide a way of uniquely identifying the receiver Smart card serial number –Prevent STBs moving to other household Second STB usually provided at lower price by network operator CA system may stop that box being given to neighbor, friend, other family member Every household must have their own subscription

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Conditional Access (CA) Integrated CA systems are unsuitable for some markets May use a pluggable CA module instead –Entire decryption solution on a PCMCIA card –Smart card plugs in to PCMCIA card –Used on retail systems to allow use with any network –Common systems include: DVB Common Interface (DVB-CI) ATSC Point Of Deployment (POD) module OpenCable CableCARD (based on POD) This has several limitations –More expensive (PCMCIA card vs. integrated smart card reader) –Very few vertical markets will use pluggable CA modules because there is no need or benefit –Also perceived as being less secure, in the case of DVB-CI Not all CA systems will support pluggable modules

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Return channel Used to communicate with the network operator or other service operator –Ordering pay-per-view services, home shopping, home banking May be used for general network access –Web browsing, , chat Many types in use –PSTN modem (usually 56K) is still the most common –Cable modem and ADSL modem are becoming more common –Exotic technologies such as GSM, DVB RCS (return channel via satellite) etc. also in limited use Not every receiver will have a return channel –Adds to the cost –Not all subscription services will need or use one

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Middleware Provides a common software platform for application development –Usually in C or Java –Every middleware platform has basically the same features Graphics & video manipulation, return channel access, access to service information, etc. Most middleware platforms today are proprietary –OpenTV (OpenTV Core) –NDS (NDS Core) –Canal+ (MediaHighway) –PowerTV (PowerTV) –Microsoft (Microsoft TV) –Nagravision-Kudelski (Tsunami) –Liberate (Liberate) But open middleware platforms are now being deployed –MHP, OCAP, ACAP, JavaTV, ARIB-B23

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Integration Cost is a major factor in STB manufacture –Especially in vertical markets –Everyone wants the product cheaper –Lots of competition –Typical cost is ~100 USD to the network operator for a standard STB Retail is more expensive Many components get integrated to save cost –Tuner and front end –Demultiplexer/MPEG decoder/CPU/graphics processor Most current STBs are one- or two-chip solutions –Depends on features needed Pressure is always towards more integrated solutions

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Block diagram of a typical receiver Tuner Smart card / CA Module MPEG-2 decoder CPU Middleware SDRAM Flash memory Graphics processor Descrambler MPEG-2 demultiplexer Front-end Standard STB with pay-TV support (integrated) BOM Cost: ~80 USD Integrated into front-end Integrated into CPU

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Three distinguishing features To use a receiver on a given network, we care about three things: –Middleware The APIs used to develop interactive applications –Conditional access system The type of encryption used to protect pay-TV content –Type of network it receives the signal from Terrestrial, cable or satellite Does it use ATSC, OpenCable, or DVB standards? These determine whether a receiver will work on a that network –Other specifications are less important –All of these features will be determined by the network operator in a vertical market

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Receiver markets Two types of market for digital TV receivers –Horizontal market (receivers sold in retail stores) Free-to-air networks Some cable networks in the USA –Vertical market (receivers supplied by network operators) Pay-TV networks in Europe and Asia Some Pay-TV networks in the USA These markets have very different business models –Thus, the pressures on the receiver manufacturer and on the spec of the receiver are also different –Which market type is best for a given manufacturer depends on their skills and strengths –Neither type of market will go away Both will likely grow in the short term Becoming more common with more digital terrestrial TV deployments and the use of open standards for middleware

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Horizontal markets Receivers are sold through retailers –E.g. electronics store, supermarket Often used for free-to-air channels only –Especially in Europe and Asia –No subscriptions needed User may be able to buy subscription from pay-TV company –Some US cable networks –Provides access to pay-TV channels as well as free-to-air channels –Uses a pluggable CA module to ensure receiver works on all networks But not every receiver in every horizontal market will include this! –More choice for the user –More scope for different types of receiver –Means the network operator doesn’t have to own the boxes Less capital investment

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Vertical markets Boxes are bought by the network operator and supplied to customers –Either rented or as part of subscription package The main model for pay-TV systems at the moment –Especially in Europe & Asia –Usually used by pay-TV satellite or cable networks Gives the network operator more control over their network –Network operator defines the hardware and software specification for the boxes –May still be supplied by more than one vendor –Gets better price because of volume discounts and guaranteed order numbers But has the costs associated with owning all of the receivers –Large capital investment –More support needed Logistics, tech support, installation, repair, etc.

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Classes of receiver Different groups have different needs from an STB –Some people want something cheap –Most people want an average box that lets them do a little bit more –Some people will pay extra for more advanced features –A few want to add DTV support to their PC Products are available for most of these groups –But some groups don’t have much choice Pay-TV operators will only support a few types of product –Supporting more is expensive –Typically will only provide an average box with some support for interactivity –May provide a more advanced box (as part of a more expensive subscription) Retail products have wider range of features and prices

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Classes of receiver – Basic ‘zapper’ Very basic hardware –Limited memory and CPU power, no return channel Usually sold retail Can receive free channels only –No support for subscription or pay-per-view channels Simple features –Channel up/down –Control audio language –Control subtitles –No program guide or other features –No interactivity

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Block diagram of a basic receiver μController SDRAM ROM Free-to-Air ‘zapper’ box BOM Cost: ~30-40 USD MPEG-2 decoder SDRAM MPEG-2 demultiplexer Tuner / Front-end

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Classes of receiver - Standard Slightly more advanced STB –More memory, faster CPU, maybe a return channel Usually sold retail or as part of a subscription May receive some pay-TV channels –Usually tied to a specific network in subscription systems –May include support for pluggable CA module in retail products Some interactivity –Program guide –Maybe games or features associated with a specific show –Maybe other interactive services offered by the network operator

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Classes of receiver - Advanced Advanced features –More memory, faster return channel, extra hardware (e.g. keyboard) Usually sold retail or as part of an advanced subscription package Receives some pay-TV channels –As for standard STB Integrates other features –E.g. PVR May include more interactive features –More applications, e.g. web browser or –Makes use of improved hardware to offer more services

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Classes of receiver – Very advanced Typically a PC with digital tuner card –Either internal or external May not be able to receive pay-TV channels –Piracy concerns may prevent this May include many advanced features –PVR, web browsing, , DVD playback –All PC applications –But the actual DTV functionality may also be very limited Not usually the main device in a home –Typically will not replace the TV/STB combination in the living room except in a very small urban home –May be used in a young person’s bedroom or university accommodation Combination device to save space

Copyright © Steven Morris 2005 All Rights Reserved Downloaded from Conclusion All DTV receivers are fairly similar –Most differences are in the software E.g. middleware, CA system Feature sets range from extremely basic to very advanced –But most boxes currently sold will have roughly the same features Middleware to provide some interactive applications (e.g. program guide and downloaded apps) PSTN modem or cable modem for return channel The move towards horizontal markets is giving more opportunities for receiver manufacturers –Markets are growing –Wider range of feature sets can be sold As markets grow, more televisions will include this functionality –Just like TVs now include cable as well as terrestrial reception