Introduction:One more pronounced in digital television and systems
Introduction:One of the major concerns of IPTV network deployment is channel change delay (also knownas zapping delay or zap time). The zap time is the total duration of time from which the viewerchanges the channel using a remote control to the point that the picture of the new channel isdisplayed. This includes the corresponding audio. These delays exist in all televisionsystems, but they are more pronounced in digital television and systems that use the internetsuch as IPTV. Human interaction with the system is completely ignored in thesemeasurements, so zap time is not the same as channel surfing.Zap time can be very disturbing for some viewers and for this reason it is considered an issuethat must be addressed in IPTV systems. The delays when changing the channel can becaused by several different factors. These factors can be classified according to the systemsthat cause them. Consequently, there are network factors, MPEG acquisition factors, and settop box buffering/decode factors. Users don't like these delays when they are watchingsomething eagerly. So, we have decided reduce such delays.? SET TOP BOX:A set-top box (STB) or set-top unit (STU) (one type also colloquially known as a cablebox) is an information appliance device that generally contains a TV-tuner input anddisplays output to a television set and an external source of signal, turning the source signalinto content in a form that then be displayed on the television screen or other displaydevice. They are used in cable television, satellite television, and over-the- air-televisionsystems, as well as other uses.Set Top Box or STB has become an integral part of TV viewing in many parts of theworld. We commonly see this sleek looking device sitting on side of TVs. Though thisdevice looks slim and simple but it is one of the most complex embedded systems today.STBs are increasing their feature set day by day. Few of the common features in currentgeneration STBs are time shift mode viewing, recording, Internet based viewing, video ondemand, Full High definition video output etc.STB is very complex embedded system; it consists of 30+ hardware blocks and similarnumber of software drivers. STB has lot of computing power distributed across mainprocessor and various co-processors. In few of top end STBs if we add operatingfrequencies of all co- processors then it would be in range of 3-4 GHz.? STB BLOCKS:1. Power Supply2. Smart Card Slot3. RAM4. STB Decoder5. Flash6. DVB-CI Slot7. Satellite Front End8. RF Modulator9. Video Interfaces10. Audio Interfaces11. Storage12. Front PanelA more logical relationship between various components is shown in following blockdiagram.Set Top Box Hardware BlocksPower Supply: This is the main power source for board. This unit generates differentvoltage required by various components on board. Input to this unit can be main line AC(220/110) or DC 12V via standalone power adapters.Smart Card Slot: This slot is provided to use smart card for Conditional Accessimplementation. Unique subscriber ID is stored on each card. Smart card is also usedin decrypting the channels.RAM: RAM is used to store all intermediate data (such as decoded video/audiobuffers) and application variables. In many cases main application is also copied to RAM andis executed from RAM to speed up the operation (as RAM is faster compared to Flash).RAM size ranges from 32MB in standard definition STBs to 256MB in some top end Full HDSTBs.STB Decoder: This is heart of the whole system. In current generation STBs most ofthe features required by STB system are integrated in STB decoder chips. This level ofintegration is called System On Chip (SoC). STB SoCs contain a large number of blocksranging from de- multiplexer to decoders and peripherals like USB, SATA etc.Flash: This is used to store boot loader, main application and other user specific nonvolatile data. Different STBs uses different sizes of flash ranging from 8MB to 64MB.DVB-CI Slot: This slot is provided to support various conditional access schemes.Conditional Access providers provide compatible DVB-CI cards to be used with STB. TheDVB-CI card decrypts the channels encrypted by Conditional Access provider as per user’ssubscription policies.Satellite Front End: Front End part of STB is responsible for receiving thebroadcasted signal, demodulating the signal and outputting digital data output for STBdecoder chip. Depending upon broadcasting environment terrestrial or satellite or cable frontend will be used. Front end unit consist of 3 main blocks tuner to tune correct frequency,demodulator to demodulate as per standard and forward error correction (FEC) unit fordata recovery.RF Modulator: This is used to modulate Audio and video into RF signal. This is mainlyto be used with older TVs which have only RF input and no composite (CVBS) input.Video Interfaces: STB decoder chip outputs video data in analog or digital format. Tomake these signals compatible with external devices, special circuitry like filter and physicalconnector are required. Current generation STBs provide many video output formatssuch as CVBS, S Video, Component video and HDMI.Audio Interfaces: STB decoder chip outputs audio data in analog as well as digitalformat. In some cases high quality DACs are used to convert digital data into analogformat. Digital data is also transmitted in digital format using SPDIF standard.Storage: Few STBs also work as digital video recorders. To aid storage of programssome storage device (HDD) is added via any of the interfaces (SATA, eSATA, ATAPI orUSB) provided by decoder chip.Front Panel: This is STBs interface to external world. Front panels are different fordifferent boxes. But most of them provide IR input/output, Status LEDs, 7 segments orLCD and few switches to configure set top box. These features are controlled byparallel IOs of main decoder chip. In some cases a dedicated microcontroller is added tofront end to reduce processing load for main chip and also to reduce the number of wiresgoing from front panel to main PCB.? STB Decoder SoCSTB Decoder is one of the most complex system on chip (SoC). There is generally onemain processor and lot of co-processor doing dedicated processing.A typical decoder SoC will have following blocks.Set Top Box Decoder blocksMain CPU: This is the main CPU executing the STB application. It is a generalpurpose CPU with lot of development tools available. Its speed range from 200MHz onstandard definition devices to near 1GHz on High Definition devices. The main CPU isgenerally based on industry standard core such Super H or ARM to improve ease oftools and reusable stack availability.Demux: Demux is a dedicated co-processor to de-multiplex the digital transport streaminto audio, video and other data. Demux checks the input stream for errors and protocolcompliance and filters the required data into desired buffers (Audio, video)Video Decoder: This co-processor is responsible for converting compressed video(MPEG) data into basic video format. Current generation decoders have programmablevideo decoders, so video decoders can support a variety of formats such as MPEG2,H264, VC1 etc.Graphics Engine: This co-processor is dedicated to graphics acceleration. Its maintask is to draw pictures and menus for user interface (UI). This unit is becoming morepowerful these days with introduction of 3D menus.Mixer: This block is responsible for mixing the video output and graphics output andproducing a final single image. This is also responsible for ordering of video and graphicsplane and transparency settings. As shown is image there are two planes one video inbackground on video plane and other is rectangular window showing program informationon graphics plane. These two planes are mixed by mixer to generate a single image.Video Output: Final result after mixing video decoder and graphics accelerator outputsis provided to video output block. This block is responsible for outputting data as perrequired standards (PAL, NTSC, SECAM, HDMI). This block generates output in analogformat using DACs. This block also generates output in digital format using HDMI convertors.Audio Decoder: Audio decoder converts the compressed audio data into basic audiodata. Audio decoders are also programmable these days. They can be programmed tosupport any audio standard. Audio decoder generally supports MPEG, AAC, Dolby formats.Audio Output: Audio output is fed to audio output block. This block provides audiooutput in analog format using internal DACs and in digital format using SPDIF convertor.Peripherals: Other than main decoders and CPU a lot of peripheral devices aresupported by STB SoCs for providing various features.USB: For record/playback on external storageSATA: used to connect HDD for providing digital video recording facility.Ethernet: Input source for IP based STBsUART: Debug port. Sometimes also used for software upgrade in fieldI2C: Used by main STB SoC to communicate with external peripheral devicessuch as front end, SCART controller, HDMI controller etc.SPI : Used for connecting to non-volatile storage on serial flash devices.? INTERNET TELEVISION:Internet television (or online television) is the digital distribution of television content,such as TV shows, via the public internet (which also carries other types of data), asopposed to dedicated terrestrial television via an over-the- air aerial system, cable television,and/or satellite television systems. It is sometimes called web television, though thisphrase is also used to describe the genre of TV shows broadcast only online.Elements:Internet television is a type of over-the- top content. ;Over-the- top; (OTT) is the deliveryof audio, video, and other media over the Internet without the involvement of a multiple-system operator (such as a cable television provider) in the control or distribution of thecontent. It has several elements.Content provider:Examples include:? An independent service, such as Netflix or Amazon Video, Hotstar, Google playmovies, myTV(Arabic), Sony LIV, Viewster, or Qello (which specializes inconcerts).? A service owned by a traditional cable, or satellite TV provider, such as Ditto TV,Sling TV (owned by Dish Network) or Direct TV (owned by AT;T).? An international movies brand, such as Eros International or Eros Now.? A service owned by a traditional film or television Networks, television channel, orcontent conglomerate, such as BBC Three since 17 Jan 2016,CBSN, CNNGo,HBONow, Now TV (owned by Sky UK), PlayStation Vue(owned by Sony), or Hulu (ajoint venture).? A peer-to- peer Video hosting service such as YouTube, Vimeo, or Crunchyroll.? Combination services like TV UOL which combines a Brazilian Internet-only TVstation with user-uploaded content, or Crackle, which combines content owned bySony Pictures with user uploaded content.? Audio-only services like Spotify, though not ;Internet television; per se, aresometimes accessible through video-capable devices in the same way.InternetThe public Internet is used for transmission from the streaming servers to theconsumer end- user.ReceiverThe receiver must have an Internet connection, typically by Wi-fi or Ethernet, and couldbe:? A web browser running on a personal computer (typically controlled by mouse andkeyboard) or mobile device, such as Firefox, Google Chrome, or Internet Explorer.? A mobile app running on a smartphone or tablet computer.? A dedicated digital media player, typically with remote control. These can take theform of a small box, or even a stick that plugs directly into an HDMI port. Examplesinclude Roku, Amazon Fire, Apple TV , Google TV, Boxee, and WD TV. Sometimesthese boxes allow streaming of content from the local network or storage drive,typically providing an indirect connection between a television and computer orUSB stick .? A Smart TV which has Internet capability and built-in software accessed with theremote control.? A Video Game Console connected to the internet such as the Xbox Oneand PS4.? A DVD player or Blu-ray disc player with Internet capabilities in addition to itsprimary function of playing content from physical discs? A set-top- box or digital video recorder (DVR) provided by the cable or satellitecompany or an independent party like TiVo, which has Internet capabilities inaddition to its primary function of receiving and recording programming from thenon-Internet cable or satellite connectionNot all receiver devices can access all content providers. Most have websites thatallow viewing of content in a web browser, but sometimes this is not done due to digital rightsmanagement concerns or restrictions. While a web browser has access to anywebsite, some consumers find it inconvenient to control and interact with content with amouse and keyboard, inconvenient to connect a computer to their television, or confusing.Manufacturers of SmartTVs, boxes, sticks, and players must decide whichproviders to support, typically based either on popularity, common corporate ownership, orreceiving payment from the provider.Display device:A display device, which could be:? A television set or video projector linked to the receiver with a video connector(typically HDMI)? A smart TV screen? A computer monitor? The built-in display of a Smart phone or tablet computerLITERATURE SURVEY(1) Title: Survey of channel switching schemes for IPTVAuthor: Daniel A. G. Manzato and Nelson L. S da Fonseca, StateUniversity of Campinas.Description: Due to the increased deployment of IPTV, variousfunctionalities are still need to be improved. The main challenge inIPTV is the reduction in startup delays. These delays are due to channelswitching. In IPTV, this delay is due to Bandwidth limitation, distributionstructure and usage of large number of buffers. Users expect channelswitching quickly. So, the delay must be reduced for few secondsor milli seconds. In Peer-to- Peer (P2P) IPTVs, there are twoapproaches for video distribution . They are tree and meshapproaches. In tree approach, multi casting application layer has adistribution structure always ready for transmission thus avoiding the over-head transmission scheduling and as a consequence, reducingstartup delay. In mesh approach, the connection is established on-demand. This reduces cost of maintaining an active distribution structure.Although, it accrues over-head for content dissemination as well asfor transmission scheduling. So, to reduce such startup delays, weuse tree approach. During channel switching, the system configurationchanges by set-top- box or computer software. It is multi-cast affiliatedwhich means that, it uses “Leave Message” to leave from “current”group and “Join Message” to join into “new” group. The protocolused here is IGMP (Internet Group Management Protocol). P2PIPTV uses multiple trees(2 trees). One tree is for admittance andanother tree is for departure during channel switching.For P2p IPTV, mesh approach is worse. Because, peers findnew neighbors before join/leave message. These delays are not only dueto network latency(exchange of signaling messages) but also dueto processing time at each node to setup corresponding network state.(2) Title: Mitigating IPTV Zapping delayAuthor: Fernando M. V. Ramos, LaSIGE/FCUL, University of LisbonDescription: An obvious way to reduce zapping delay is to encodethe video stream with a higher frequency of I-frames. However, asexplained earlier, such a scheme would significantly increase thestorage needs at the video server as well as the band-width needed tooffer the service. This is therefore not a practical solution. Morefeasible solutions include the optimization of channel streamingand playout. The variation of playout speed of media frames depending onchannel conditions allows the client to buffer less data, thusintroducing less delay, for a given level of protection against bufferunderflow. In this scheme, the client varies the rate at which it plays outaudio and video according to the state of its playout buffer. Whenthe buffer occupancy is below a desired level, the client plays themedia slowly, generating unnoticeable latency. This latency isthen eliminated with periods of faster-than- normal playout.The user starts by issuing a channel change request using theremote control. The request reaches the set-top box (STB) after anestimated 5–10 ms delay. In IPTV video delivery, in contrast to cablenetworks, for instance, typically only the channel the user is watching isdelivered to the STB at any one time. This is due to bandwidthlimitations in the access network. When a user switches to a new channel,the STB has to issue a new channel request toward the network. Tominimize this component of the delay, all TV channels are distributedvery close to the user, commonly to the digital subscriber line accessmultiplexer (DSLAM, in DSL networks) or the local router. In addition tothis signaling delay we need to add the propagation delay experienced inthe access link. The sum of these types of delay, to which we jointly referas network delay, is usually below 100–200 ms.(3) Title: A Software and Hardware IPTV Architecture for Scalable DVBDistributionAuthor: Georg Acher, Detlef Fliegl and ThomasFuhrmannDescription: An IPTV architecture that is fully compatible to existingdigital television broadcast systems. This allows an easyconvergence of digital television and IPTV. During the transition,consumers can thus benefit from the advantages of both technologies.In traditional broadcast systems, this would be called simulcast. IPTVallows convergent deliverance of television content over IP.Convergence does not require restoring all physical capabilities ofdifferent transport media even though it is desirable. Therefore, theresulting feature set and quality of the encoded media streams maychange.Zapping mostly takes place between adjacent channels of a knownlist. When switching to a channel the client application joins the multicastgroup of the next channel in the list. If zapping continues the streamof the next channel is already present. As soon as a channel getswatched for a while the multicast group of the next channel is beingdropped again.With 3 clients continuously tuning to random services with multiplePIDs on random DVB-S/S2 transponders, the latency varies between 70ms and about 2 s with an average of about 0.5 s. The lower zappingtimes occur when a tuner already has a lock and only the PID filteringneeds to be modified. The average latency is mainly determined by thetuning itself and includes the time to acquire a lock (50–200 ms) andthe DiseqC- communication to the LNB (about 100 ms). Zapping timesover 1s happen only with a probability of less than 10% and aremainly caused by missing a multicast listener report at the server whichis sent by the client every second.(4) Title: Subscription-free Pay-TV over IPTVAuthor: Tolga Arul, Abdulhadi ShoufanbDescription: With the ever-expanding broadband networkconnectivity, television and Internet are converging and theInternet Protocol Television (IPTV) is gaining in importanceincreasingly. IPTV is one of altogether four transmission paths forbroadcast television alongside cable, satellite and free-to- airtransmissions. It differs considerably from web-TV, which has differentrequirements on the network infrastructure and therefore also usesdifferent protocols. Enabled by its return channel, IPTV ischaracterized by several developments such as time-, device- andplace-shifted viewing. Similarly to conventional television, the IPTVstandards support pay-TV. Pay-TV is a business model for fundingbroadcast transmission of media content, where the subscriber has topay for the provided content. The market for pay-TV shares more than40% of the total TV industry worldwide. Currently, there are threemajor charging models, which are used for pay-TV in broadcasttransmissions: subscription-based charging, Video on Demand, andpay-per- view. However, each charging model has several shortcomingswith regard to attribution of usage costs, availability of an upper limitfor costs, interactivity of entitlement and the adaptability of services.When subscription-based charging is used, users need to take out amonthly or an annual subscription for some channel or channel package,in which they are interested. This subscription-based pricing model offerstwo main advantages for users regarding convenience and insurance.Specifically, subscribed members, on the one hand, do not need todeliberate upon cost and benefit each time they want to view somecontent. On the other, the fixed-price subscription model protects usersfrom surprisingly high bills.(5) Title: The Analysis and Research of IPTV Set-top Box SystemAuthor: Fangyan Bai, Qi SunDescription: IPTV set-top box basic system structure can be dividedinto front-end devices, networks, and the receiving end three parts, eachpart consists of a number of key equipment, while the completion ofappropriate basic functionality, also to ensure the smooth operation ofIPTV TV business. On one hand, The box receives IP network port datastream through Ethernet interface, after decode, descramble,demodulation, and then make the video and audio D/A convert, they willbecome the analog signal that can be recognized by the TV, and betransmitted to the TV. On the other hand, it receives control commandsfrom the TV and send to the IP network server-side. The primaryfunction of IP network server is to send the appropriate data to theclient according to the TV instructions received by the box. Tocomplete the function of the system, it needs the cooperation of IPTVset-top box, IP server and TV communication. Set-top box systemarchitecture consists of three independent subsystems: TV Unit, PCunit and conditional access (encryption systems, CA) units. TVsubsystem is composed of tuner and video decoders, which used tohandle digital streaming information; CA subsystem service providerswith control capabilities, users can achieve close monitoring andmanagement, to know when the user watches what programmes; PCsubsystem are largely modular designs, STB designers can increase ordecrease depending on the needs of the components in the system, sinceIPTV STB's goal is to provide Internet services, its PC systems haveagreed to provide TCP/IP stack, and has better stocks.IPTV can use different physical network to send video programcontent and signal to a user effectively in the form of IP packet safety, itis an advanced system integration technology. Its basic forms are: contentdistribution and digital copyright technology, audio and video codec,broadband access technology, IP broadcast, multicast technology.