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An introduction to DTV receiver technology

An introduction to DTV receiver technology. Steve Morris steve.morris@mhp-interactive.org. 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

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An introduction to DTV receiver technology

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  1. An introduction to DTV receiver technology Steve Morris steve.morris@mhp-interactive.org Downloaded from http://www.interactivetvweb.org

  2. 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 Downloaded from http://www.interactivetvweb.org

  3. 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 Downloaded from http://www.interactivetvweb.org

  4. Block diagram of a typical receiver Tuner Front-end Descrambler Smart card / CA Module MPEG-2 demultiplexer SDRAM MPEG-2 decoder Graphics processor CPU Flash memory Middleware Downloaded from http://www.interactivetvweb.org

  5. 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 Downloaded from http://www.interactivetvweb.org

  6. 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 Downloaded from http://www.interactivetvweb.org

  7. 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 Downloaded from http://www.interactivetvweb.org

  8. 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 Downloaded from http://www.interactivetvweb.org

  9. 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: • NDS (VideoGuard) • Nagravision-Kudelski (Nagravision) • Conax (Conax) • Motorola • France Telecom (Viacess) • Canal + (MediaGuard) • Philips (Cryptoworks) • Irdeto (IrdetoAccess) • General Instrument (DigiCypher II) Downloaded from http://www.interactivetvweb.org

  10. 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 Downloaded from http://www.interactivetvweb.org

  11. 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 Downloaded from http://www.interactivetvweb.org

  12. 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, email, 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 Downloaded from http://www.interactivetvweb.org

  13. 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 Downloaded from http://www.interactivetvweb.org

  14. 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 Downloaded from http://www.interactivetvweb.org

  15. Block diagram of a typical receiver Tuner Front-end Descrambler Smart card / CA Module MPEG-2 demultiplexer SDRAM Standard STB with pay-TV support (integrated) BOM Cost: ~80 USD MPEG-2 decoder Graphics processor CPU Integrated into front-end Integrated into CPU Flash memory Middleware Downloaded from http://www.interactivetvweb.org

  16. 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 Downloaded from http://www.interactivetvweb.org

  17. 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 Downloaded from http://www.interactivetvweb.org

  18. 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 Downloaded from http://www.interactivetvweb.org

  19. 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. Downloaded from http://www.interactivetvweb.org

  20. 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 Downloaded from http://www.interactivetvweb.org

  21. 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 Downloaded from http://www.interactivetvweb.org

  22. Block diagram of a basic receiver Tuner / Front-end Free-to-Air ‘zapper’ box BOM Cost: ~30-40 USD MPEG-2 demultiplexer SDRAM SDRAM MPEG-2 decoder μController ROM Downloaded from http://www.interactivetvweb.org

  23. 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 Downloaded from http://www.interactivetvweb.org

  24. 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 email • Makes use of improved hardware to offer more services Downloaded from http://www.interactivetvweb.org

  25. 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, email, 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 Downloaded from http://www.interactivetvweb.org

  26. 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 Downloaded from http://www.interactivetvweb.org

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