Home cinema, also called home theater, seeks to reproduce cinema quality video and audio in the home. Technically, a home cinema could be as basic as a simple arrangement of a television, DVD, and a set of speakers. It is therefore difficult to specify exactly what distinguishes a "home cinema" from a "television and stereo". Most people in the consumer electronics industry would agree that a "home theater" is really the integration of a relatively high-quality video output with surround sound. Design A Home Theater Today, "home cinema" implies a real "cinema experience" and therefore a higher quality set of components than the average television provides. A typical home theater includes the following parts: 1.) Input Devices: One or more audio/video sources. High quality formats such as HD DVD or Blu-ray are preferred, though they often include a VHS player or Video Game Systems. Some home theatres now include a home theater PC to act as a library for video and music content. 2.) Processing Devices: Input devices are processed by either a standalone AV receiver or a Preamplifier and Sound Processor for complex surround sound formats. The user selects the input at this point before it is forwarded to the output. 3.) Audio Output: Systems consist of at least 2 speakers, but can have up to 11 with additional subwoofer. 4.) Video Output: A large HDTV display. Options include Liquid crystal display television (LCD), video projector, plasma TV, rear-projection TV, or a traditional CRT TV. 5.) Atmosphere: Comfortable seating and organization to improve the cinema feel. Higher end home theaters commonly also have sound insulation to prevent noise from escaping the room, and a specialized wall treatment to balance the sound within the room. Home Theatre Flow Diagram Component systems vs. Theater-in-a-Box High-quality home cinemas are assembled from component pieces purchased separately to provide the best combination of equipment for the cost. It is possible to purchase home theater in a box kits that include a set of speakers for surround sound, an amplifier/tuner for adjusting volume and selecting video sources, and sometimes a DVD player. Though these kits often pale in comparison to a custom-built home cinema, they are inexpensive and easy to set up; one needs only to add a television and some movies in order to create a simple home theater. Dedicated home theaters Some home cinema enthusiasts go so far as to build a dedicated room in the home for the theater. These more advanced installations often include sophisticated acoustic design elements, including "room-in-a-room" construction that isolates sound and provides the potential for a nearly ideal listening environment. These installations are often designated as "screening rooms" to differentiate from simpler installations. This idea can go as far as completely recreating an actual cinema, with a projector enclosed in a projection booth, specialized furniture, a piano or theatre organ, curtains in front of the projection screen, movie posters, or a popcorn or snack machine. More commonly, real dedicated home theaters pursue this to a lesser degree. Presently the days of the $100,000 and over home theater is being usurped by the rapid advances in digital audio and video technologies, which has spurred a rapid drop in prices. This in turn has brought the true digital home theater experience to the doorsteps of the do-it-yourself people, often for less than what you would expect to pay for a low budget economy car. Current consumer level A/V equipment can meet and often exceed in performance what you would expect to experience at a modern commercial theater. Home Theater Seating Home theater seating consists of chairs specifically engineered and designed for viewing movies in a personal home theater setting. Most home theater seats share these features: A cup holder built into the chairs' armrests and a shared armrest between each seat. Home theater seating come in two basic varieties: 1. Movie theater style chairs like those seen in a movie cinema, which features a flip up seat cushion, or 2. Plush leather reclining lounger type of home theater seating with a flip out footrest. Additional features like storage compartments, snack trays, tactile transducers, or even electric motors to recline the chair are available, depending on the model. Backyard theater In places that have the proper outdoor atmosphere, it is possible for people to set up a home theater in their backyard. Depending on the space available, it may simply be a temporary version with foldable screen, a projector and couple of speakers, or a permanent fixture with huge screens and dedicated audio set up poolside. Due to the outdoor nature, it is quite popular with BBQ parties and pool parties. Some people have built upon the idea, and constructed mobile drive-in theaters that can play movies in public open spaces. Usually, these require a powerful projector, a laptop or DVD player, outdoor speakers and/or an FM transmitter to broadcast the audio to other car radios History of Home Theater 1950s and 1960s home movies In the 1950s, home movies became popular in the United States and elsewhere as Kodak 8 mm film (Pathé 9.5 mm in France) and camera and projector equipment became affordable. Projected with a small, portable movie projector onto a portable screen, often without sound, this system became the first practical home theater. They were generally used to show home movies of family travels and celebrations but also doubled as a means of showing private stag films. Dedicated home cinemas were called screening rooms at the time and were outfitted with 16 mm or even 35 mm projectors for showing commercial films. These were found almost exclusively in the homes of the very wealthy, especially those in the movie industry. Portable home cinemas improved over time with color film, Kodak Super 8 mm film film cartridges, and monaural sound but remained awkward and somewhat expensive. The rise of home video in the late 1970s almost completely killed the consumer market for 8 mm film cameras and projectors, as VCRs connected to ordinary televisions provided a simpler and more flexible substitute. 1980s home cinema The development of multi-channel audio systems and laserdisc in the 1980s created a new paradigm for home cinema. The first known home cinema system was installed as a sales tool at Kirshmans furniture store in Metairie, Louisiana in 1974. They built a special sound room which incorporated the earliest quadraphonic audio systems and modified Sony trinitron televisions for projecting the image. Many systems were sold in the New Orleans area in the ensuing years before the first public demonstration of this integration occurred in 1982 at the Summer Consumer Electronics Show in Chicago, Illinois. Peter Tribeman of NAD (USA) organized and presented a demonstration made possible by the collaborative effort of NAD, Proton, ADS, Lucasfilm and Dolby Labs who contributed their technologies to demonstrate what a home cinema would "look and sound" like. Over the course of three days, retailers, manufacturers, and members of the consumer electronics press were exposed to the first "home like" experience of combining a high quality video source with multi-channel surround sound. That one demonstration is credited with being the impetus for developing what is now a multi-billion dollar business. 1990s home cinema Before the arrival of DVD. A typical 1990's Home Cinema would more than definitely have a Laserdisc player nestled right at the heart of it. Laserdiscs adopted what was back then, coded as AC3 (Dolby Digital5.1) sound, along with the rarer DTS sound found on some rarer specialist DTS encoded Laserdiscs. S-VHS players were the most popular and the most affordable. Large screen - Rear Projection TV's were mostly used throughout the 1990's. In the late 1990s, the development of DVD, 5.1-channel audio, and high-quality video projectors that provide a cinema experience at a price that rivals a big-screen HDTVs sparked a new wave of home cinema interest. HOME THEATER DESIGN IDEAS Source Jay Tayborg Room Dimensions The first thing we needed to decide was the room dimensions. I had three key goals for this theater which impact this decision: The room dimension ratios should be as acoustical optimal as possible. The display system should be rear projection to move the noisy projector (and other equipment) away from the listening position and improve the quality of the image when the room lights are not all the way off. The room should seat a minimum of six people using normal sofas (my wife doesn't like theater seating). In average size home theaters and listening rooms, the axial resonances (frequency at which the wavelength of the sound matches the room dimension) falls in the first few octaves of the audible sound spectrum. These resonances cause significant peaks and dips in the frequency response as heard in the room. To minimize the impact of these resonances, the room dimensions (length, width, height) are chosen so that they are not equal or an even multiple of one another. This essentially spreads out the resonances so that one frequency (or narrow range) is not affected by resonances along more than one room axis. A number of researchers have attempted to determine the optimal ratio for a rectangular room. The consensus is that there is no "optimal" ratio, but a number of different ratios that provide good distributions of room resonances. Some have chosen a ratio (1.0 : 1.6 : 2.33) proposed by L. W. Sepmeyer (Computer Frequency and Angular Distribution of the Normal Modes of Vibration in Rectangular Rooms, 1965). However making the wall between the theater and projection room acoustically transparent, effectively making the length of the room considerably longer. Larger rooms have fewer bass resonance problems because the modes are closer together in the audible frequency range. We're only increasing one of the room dimensions, but this is the most important dimension since this will make the bass response much smoother as we move forward and back in the room, giving us more flexibility in adjusting the seating positions. The effect of room modes can be reduced by using low frequency absorption in the room. This absorption broadens the bandwidth of each mode and reduces its amplitude. Low frequency absorption can be provided by appropriate room construction and using acoustic treatments designed for this purpose (such as RPG Modex panels and ASC Tube Traps, or similar homemade devices). A properly designed room with these treatments will result in a much smoother bass response, but more bass energy must be provided by the subwoofers to create the same bass loudness in the room. Increasing the length of the room also means that the rear wall is now a considerable distance from the speakers. This eliminates the rear room boundary from interfering with the front speaker response. Room boundaries can also have significant deleterious effect on frequency response smoothness. This is due to constructive and destructive interference between the direct sound from the speakers and the reflected sound from the walls. The projector room can also now be used for room acoustic treatments without worrying about esthetics. And the subwoofers can be placed in ideal positions to more evenly "load" the room so the bass response is more even throughout the entire listening area. The dimensions of the "theater" part of the room are 258" long, 178" wide, and 110" high. This room is separated from the projector room with a cloth partition. The length of the overall room is 442". Reverberation After considering room bass resonances, the most significant acoustical property of a room is its reverberation time. When a sound is generated in a room, it bounces around the room and eventually decays. The accepted definition of reverberation time is the time it takes sound to be attenuated by 60dB. In rough terms, this is the time it takes a loud sound to decay to inaudibility. A room with a long reverberation time will sound very live, perhaps even to the point of having echoes if the room is large enough. Many church cathedrals or gymnasiums will have this quality. A room with a very short reverberation time will sound dead and lifeless - an anechoic chamber or an open field are probably the best examples. There are many opinions about the optimum reverberation time for a home theater, but it is generally agreed that a reverberation time in the range of 0.2 to 0.6 seconds will work well. A longer reverberation time will make music sound more live, but at the expense of dialog intelligibility. Since movies are mostly about the dialog, I've designed the theater with a reverberation time goal of around 0.3 to 0.4 seconds. This is similar to my previous theater which worked very well. Reverberation time is determined by the size of the room and acoustic dampening. Acoustic dampening materials attenuate the sound as it reflects off the surface. Every material used in the room provides some acoustic dampening, so the challenge is to choose materials for their esthetic value that also provide good acoustical properties. For optimal sound, the reverberation time should be fairly consistent across the audible spectrum. It is fairly easy to absorb sound in the higher frequencies with materials such as carpeting, stuffed furniture, draperies, etc., but it is more difficult to match this absorption in the bass frequencies. The reverberation time can be approximated using the following simple formula, which was empirically derived by Sabine around the turn of the century. It should be noted, however, that this formula is not very accurate for small rooms, and empirical measurements will be required to fine tune the room. RT = 0.049V/Sa where, V = volume of the room in cu ft. S = total surface area of the room in sq ft. a = the average absorption coefficient of room surfaces. Sa = total absorption, sabins. The absorption coefficients of most building and acoustic materials are readily available. These are generally specified for six different frequencies (125Hz, 250Hz, 500Hz, 1KHz, 2KHz, and 4KHz). Please find below an example spreasheet from a theater to estimate the reverberation time based on the materials and room treatments. The determination of room treatments was partially determined by plugging their acoustical properties into this spreadsheet to see their effect. The calculated reverberation time for my theater ranges from 0.25 to 0.4 across the audio spectrum (at least from 125Hz to 4Khz). However, it is difficult to estimate the absorption that will result from the rear projector room. It was modeled this as open space (i.e., high absorption across the spectrum), and this seems to have been fairly accurate since the reverberation time inside the theater sounds that were expected. Size: 21.5 x 14.8 x 9.2 Floor Carpet with mat over suspended wood, vinyl sheeting between pad and carpet Walls Left 5/8" drywall over frame construction with fiberglass Right 5/8" drywall on hat channel with RSICs at 16" and 32" centers, with fiberglass insulation Front Guilford FR701 fabric, open to projector room, projection screen, 5/8" drywall above screen Rear 5/8" drywall over frame construction with fiberglass, topped with 1/2" plywood Ceiling 5/8" drywall on hat channel with RSICs over frame construction with fiberglass Volume: 2897 cu ft. Material S 125 Hz 250 Hz 500 Hz 1 Khz 2 Khz 4 Khz sq ft. a Sa a Sa a Sa a Sa a Sa a Sa Carpet with pad over wood floor 196 0.10 19.6 0.27 52.8 0.39 76.2 0.34 66.5 0.48 93.8 0.63 123.2 Carpet with pad over wood riser 123 0.40 49.3 0.35 43.2 0.39 48.1 0.34 41.9 0.48 59.2 0.63 77.7 Left wall (- acoustic treatment) 171 0.29 49.5 0.10 17.1 0.05 8.5 0.04 6.8 0.07 12.0 0.10 17.1 Right wall (- acoustic treatment, door) 165 0.34 56.0 0.20 33.0 0.06 9.9 0.04 6.6 0.07 11.5 0.10 16.5 Uncovered door 6 Back wall (- acoustic treatment) 78 0.29 22.6 0.10 7.8 0.05 3.9 0.04 3.1 0.07 5.4 0.10 7.8 Front wall (- screen & above) 90 0.85 76.2 0.85 76.2 0.85 76.2 0.85 76.2 0.90 80.7 1.00 89.6 Front wall above screen 17 0.29 4.9 0.10 1.7 0.05 0.8 0.04 0.7 0.07 1.2 0.10 1.7 Rear projection screen 30 0.35 10.4 0.25 7.4 0.18 5.3 0.12 3.6 0.07 2.1 0.04 1.2 Ceiling (-acoustic treatment) 294 0.34 100.0 0.20 58.8 0.06 17.7 0.04 11.8 0.07 20.6 0.04 11.8 Air (per 1000 cu ft) 2.9 0.00 0.0 0.00 0.0 0.00 0.0 0.90 2.6 2.30 6.7 7.20 20.9 Acoustic Treatments Left wall fiberglass absorption 15 0.90 13.5 0.92 13.8 1.00 15.0 1.00 15.0 1.00 15.0 1.00 15.0 Left wall angled reflectors 12 0.34 4.1 0.69 8.3 0.26 3.1 0.14 1.7 0.17 2.0 0.20 2.4 Right wall fiberglass absorption 15 0.90 13.5 0.92 13.8 1.00 15.0 1.00 15.0 1.00 15.0 1.00 15.0 Right wall angled reflectors 12 0.34 4.1 0.69 8.3 0.26 3.1 0.14 1.7 0.17 2.0 0.20 2.4 Rear wall bass trap diffusors 58 1.40 81.7 1.80 105.0 1.50 87.5 0.90 52.5 0.50 29.2 0.30 17.5 Ceiling Skyline diffusors 24 0.00 0.0 0.34 8.2 0.28 6.7 0.29 7.0 0.19 4.6 0.16 3.8 Audience (on leather sofas) 7 4.00 28.0 5.00 35.0 5.50 38.5 6.50 45.5 5.20 36.4 4.00 28.0 Total Sabins 533.3 490.2 415.6 358.1 397.4 451.5 Reverberation Time 0.27 0.29 0.34 0.40 0.36 0.31 Room Construction Two primary goals for room construction are noise isolation and good acoustical properties. Fortunately, conventional home building practices (specifically, drywall over framing) yield very good acoustics for small to moderate size rooms. To improve the acoustics from a cement floor, it would be recomended that the floor be built up with flooring plywood over 2x4 joists. Relatively thin (1/2") plywood is used for the floor to reduce the resonance frequency and increase low frequency absorption. Floor joists are spaced at random intervals through the room to vary the resonance frequencies. Closer spacing is used under higher traffic areas to firm up the floor. Sound absorbing material is used in between the floor joists. To reduce high frequency absorption from the carpet, vinyl sheeting is placed between the carpet and the pad on the rear shelf. The walls and ceiling are built using 5/8" drywall on framing which provides excellent acoustic properties (although some surface-applied acoustic treatment is still required for the best sound). My primary concern for the walls and floor construction is reducing sound transmission, both to avoid bothering family members outside the theater and to reduce ambient noise in the theater. The shared wall is built using double wall construction (two completely independent walls are built with an air gap separating them). This kind of wall construction provides more than 20dB of additional sound isolation compared to a normal stud partitioned wall. The drywall for this wall is mounted on hat channel using resilient sound isolation clips. The ceiling also uses 5/8" drywall mounted to hat channel using RSICs. 8" fiberglass batting with a 4" air gap is used between the floor joists. The ceiling is completely sealed to eliminate sound leakage. Acoustic Treatment Acoustic treatment can be applied to the surface of the walls to modify the acoustics of the space, including adjusting reverberation time, reducing room resonance problems, reducing comb-filter effects, and improving imaging specificity by reducing early reflections.Sound reflecting off of walls and other objects in the room can reduce detail and imaging specificity. Sound reflections fall into two categories - those that can be distinguished from the original sound and those that can't. Sounds that occur more than 10ms apart can generally be distinguished as separate sounds. Since sound travels at roughly 1100 ft per second, a reflection from a wall that adds 11 ft to the travel distance will fall into this first category. Shorter delays will fall into the second category. Reflections that can't be distinguished are generally the most harmful to the imaging. This is because these reflections confuse the brain's ability to determine spatial cues from the difference in arrival time to your two ears. The closer in time the reflection is to the original sound, the worse the problem. This is why refraction off the edge of a speaker cabinet can be so damaging to a speakers ability to image well. Longer delayed reflections can actually be helpful to creating a sense of airiness to the sound as long as the reflections are not high in energy compared to the original. In most rooms, these reflections will be fairly diffuse once they reach your ears. The other advantage of taming the first reflections is the reduction of comb filtering. These reflections can also cause constructive and destructive interference at low frequencies which result in peaks and dips in the frequency response. By reducing the amplitude of the coherent reflections, these interference effects are mitigated. The obvious way to reduce the effect of reflections is to put acoustic absorbing material on the surface of the room. However, too much use of these materials can reduce the reverberation time of the room to the point that the room sounds dead and flat. The alternative is to scatter or diffuse the sound so that only a small portion of the energy from the reflection actually arrives at your ear and the rest is reflected to other parts of the room. Using a small amount of absorptive material (shown as peach colored rectangles in the diagram above) at the first reflection point on the side walls since this is where the strongest reflections usually occur (since the floor is carpeted, it already has good absorption). The side wall absorptive material consists of 4" thick fiberglass batting set into the wall. Vertical slats are placed periodically between the batting which helps to diffuse the sound reflections within the batting, increasing its absorptive capability (particularly in the mid frequencies). The side walls beside the listening position are treated with slanted plywood panels. This reduces "slap echo" which is caused from mid to high frequency sounds reflecting back and forth across the room. I've also placed some fiberglass absorption material around the side channel speakers to reduce near wall reflections from these speakers. The rear wall requires the most treatment since the rear seating is relatively close to this wall. Direct reflections from a close wall can reduce image detail and cause interference effects affecting frequency response. One does not want to use too much absorptive material on this wall because this might make the room ACOUSTIC TREATMENTS ON REAR WALL sound too dead, particularly for those seated in the rear seating positions. Some form of diffusor is the right solution since this will diminish the effect of direct reflections while maintaining a degree of ambiance in the room. I decided to make polycylindrical diffusors which double as bass traps, similar to ASC Tube Trap half-rounds. A polycylindrical diffusor is not quite as effective as a reflection phase grating diffusor (such as those popularized by RPG Diffusors), but it still works well and can be produced at a fraction of the cost and complexity. A total of 16 diffusors, each 15"w x 36"h, are used on the real wall, as shown in the diagram above. Acoustic treatment can also be used to reduce the effect of room modes. By increasing the absorption of bass energy, the amplitude of frequency response deviations from room modes is decreased, while at the same time spreading out their effect over a wider range of frequencies. Much of the bass absorption will come from the room construction. The floor, walls, and ceiling are all designed to be relatively flexible with a low resonance frequency, allowing bass energy to be absorbed and dissipated. Since the rear seating is relatively close to the rear wall, additional bass absorption in this area will be beneficial at reducing room mode induced bass peaks in the region of these seats. The diffusors are designed to provide bass absorption in the 80-300Hz region which is where many of the room mode problems are likely to occur. Since these diffusors are not terribly efficient bass absorbers, the large number used (16 in my case) is necessary to have a meaningful effect on reducing room mode bass irregularities. Seating Leather sofas and loveseats are provided for seating for seven people. A 12" riser is used in the rear 100" of the room for the two love seats for a clear line of sight to the screen. Most seats are positioned such that expected head positions are not on even multiples of the room dimensions. This minimizes the effect of room resonances. The only significant exception is the center seat on the front sofa, but this position will provide the best imaging response. Lighting and Ventilation Lighting is provided by low voltage cans in the ceiling over each sofa and sconces on the side walls. There is also a rope light mounted under a lip on the riser. All of these lights are on dimmer controls. Since the theater is a well sealed room, some forced ventilation is required to maintain fresh air. Since there is no equipment inside the theater (other than speakers), relatively little heat will be generated in the room, so little cooling is required. A separate zone on the central air conditioning/heat pump is provided for the theater. The intake vent is mounted over the screen in the front of the room. The exhaust vent is mounted in the floor behind the rear loveseats. Ducting is implemented with flexible fiberglass lined ducts to minimize sound transmission A home theater is best implemented in a dedicated room that can be sound proofed and closed off from light. I prefer my music system in the living room where it can provide background tunes for socializing, as well as be used for focused listening. WHAT IS IPTV? IPTV (Internet Protocol Television) is a system where a digital television service is delivered by using Internet Protocol over a network infrastructure, which may include delivery by a broadband connection. A general definition of IPTV is television content that, instead of being delivered through traditional broadcast and cable formats, is received by the viewer through the technologies used for computer networks. For residential users, IPTV is often provided in conjunction with Video on Demand and may be bundled with Internet services such as Web access and VoIP. The commercial bundling of IPTV, VoIP and Internet access is referred to as "Triple Play" service (adding mobility is called "Quadruple Play"). IPTV is typically supplied by a service provider using a closed network infrastructure. This closed network approach is in competition with the delivery of TV content over the public Internet, called Internet Television. In businesses, IPTV may be used to deliver television content over corporate LANs. Because IPTV uses huge centralized servers to deliver video into consumers' homes, it can support a nearly unlimited number of channels and allow customers to pick from an ŕ la carte channel selection. It can even offer multiple camera angles for sporting events and make thousands of old movies, TV shows, and events available "on demand" at the push of the button. IPTV differs from earlier forms of Internet-based TV in that, while the video signal is encoded just like data over the Web, it travels solely over SBC's own servers and network. Viewers will find the experience akin to watching digital cable, rather than streaming video on the Web. Architecture of IPTV Broadcast IPTV has two major architecture forms: free and fee based. As of June 2006, there are over 1,300 free IPTV channels available. This sector is growing rapidly and major television broadcasters worldwide are transmitting their broadcast signal over the Internet. These free IPTV channels require only an Internet connection and an Internet enabled device such as a personal computer, HDTV connected to a computer or even a 3G cell/mobile phone to watch the IPTV broadcasts. See also: Internet television Mobile TV In December 2005, independently produced mariposaHD became the first original IPTV broadcast available in an HDTV format. Various Web portals offer access to these free IPTV channels. Some cite the ad-sponsored availability of TV series such as Lost as indicators that IPTV will become more prevalent. Because IPTV uses standard networking protocols, it promises lower costs for operators and lower prices for users. Using set-top boxes with broadband Internet connections, video can be streamed to households more efficiently than current coaxial cable. ISPs are upgrading their networks to bring higher speeds and to allow multiple High Definition TV channels. In 2006, AT&T launched its U-Verse IPTV service. Comprised of a national head end and regional video serving offices, AT&T offered over 300 channels in 11 cities with more to be added in 2007 and beyond. While using IP protocols, AT&T has built a private IP network exclusively for video transport. Local IPTV, as used by businesses for Audio Visual AV distribution on their company networks is typically based on a mixture of: a) Conventional TV reception equipment and IPTV encoders b) IPTV Gateways that take broadcast MPEG channels and IP wrap them to create multicast streams. IPTV uses a two-way digital broadcast signal sent through a switched telephone or cable network by way of a broadband connection and a set-top box programmed with software (much like a cable or DSS box) that can handle viewer requests to access to many available media sources. Currently, California based UTStarcom, Inc. and Tennessee based Worley Consulting are two companies offering end-to-end networking infrastructure for IPTV-based services. Protocols IPTV covers both live TV (multicasting) as well as stored video (Video on Demand VOD). The playback of IPTV requires either a personal computer or a set-top box connected to a TV. Video content is typically compressed using either a MPEG-2 or a MPEG-4 codec and then sent in an MPEG transport stream delivered via IP Multicast in case of live TV or via IP Unicast in case of Video on Demand. IP Multicast is a method in which information can be sent to multiple computers at the same time. The newly released (MPEG-4) H.264 codec is increasingly used to replace the older MPEG-2 codec. In standards-based IPTV systems, the primary underlying protocols used for: Live TV is using IGMP version 2 for connecting to a multicast stream (TV channel) and for changing from one multicast stream to another (TV channel change). VOD is using the Real Time Streaming Protocol (RTSP). Currently, the only alternatives to IPTV are traditional TV distribution technologies such as terrestrial, satellite and cable. However, cable can be upgraded to two-way capability and can thus also carry IPTV. NPVR (network-based Personal Video Recorder) Network Personal Video Recording is a consumer service where real-time broadcast television is captured in the network on a server allowing the end user to access the recorded programs on the schedule of their choice, rather than being tied to the broadcast schedule. The NPVR system provides time-shifted viewing of broadcast programs, allowing subscribers to record and watch programs at their convenience, without the requirement of a truly personal PVR device. It could be compared as a "PVR that is built into the network" -- however that would be slightly misleading unless the word "Personal" is, of course, changed to "Public" for this context. Subscribers can choose from the programmes available in the network-based library, when they want, without needing yet another device or remote control. However, many people would still prefer to have their own PVR device, as it would allow them to choose exactly what they want to record. This bypasses the strict copyright and licensing regulations, as well as other limitations, that often prevent the network itself from providing "on demand" access to certain programmes (see Heroes, below). In Greece, On Telecoms offers an NPVR service to all subscribers in their basic package with all the programming of all major national Greek TV channels for the last 72 hours. The user has to sign in their contract that they agree that the company will record national programming of the last 72 hours FOR them so that they can come around any legal implications (like the ones mentioned here) as this service would work like a personal PVR. Advantages The IP-based platform offers significant advantages, including the ability to integrate television with other IP-based services like high speed Internet access and VoIP. A switched IP network also allows for the delivery of significantly more content and functionality. In a typical TV or satellite network, using broadcast video technology, all the content constantly flows downstream to each customer, and the customer switches the content at the set-top box. The customer can select from as many choices as the telecomms, cable or satellite company can stuff into the “pipe” flowing into the home. A switched IP network works differently. Content remains in the network, and only the content the customer selects is sent into the customer’s home. That frees up bandwidth, and the customer’s choice is less restricted by the size of the “pipe” into the home. This also implies that the customer's privacy could be compromised to a greater extent than is possible with traditional TV or satellite networks. Interactivity An IP-based platform also allows significant opportunities to make the TV viewing experience more interactive and personalized. The supplier may, for example, include an interactive program guide that allows viewers to search for content by title or actor’s name, or a picture-in-picture functionality that allows them to “channel surf” without leaving the program they’re watching. Viewers may be able to look up a player’s stats while watching a sports game, or control the camera angle. They also may be able to access photos or music from their PC on their television, use a wireless phone to schedule a recording of their favorite show, or even adjust parental controls so their child can watch a documentary for a school report, while they’re away from home. VoD VoD stands for Video on Demand. VoD permits a customer to browse an online programme or film catalogue, to watch trailers and to then select a selected recording for playback. The playout of the selected movie starts nearly instantaneously on the customer's TV or PC. Technically, when the customer selects the movie, a point-to-point unicast connection is set up between the customer's decoder (SetTopBox or PC) and the delivering streaming server. The signalling for the trick play functionality (pause, slow-motion, wind/rewind etc.) is assured by RTSP (Real Time Streaming Protocol). The most common codecs used for VoD are MPEG-2, MPEG-4 and VC-1. In an attempt to avoid content piracy, the VoD content is usually encrypted. Whilst encryption of satellite and cable TV broadcasts is an old practice, with IPTV technology it can effectively be thought of as a form of Digital Rights Management. A film that is chosen, for example, may be playable for 24 hours following payment, after which time it becomes unavailable. IPTV based Converged Services Another advantage of an IP-based network is the opportunity for integration and convergence. Converged services implies interaction of existing services in a seamless manner to create new value added services. One good example is On-Screen Caller ID, getting Caller ID on your TV and the ability to handle it (send it to voice mail, etc). IP-based services will help to enable efforts to provide consumers anytime-anywhere access to content over their televisions, PCs and cell phones, and to integrate services and content to tie them together. Within businesses and institutions, IPTV eliminates the need to run a parallel infrastructure to deliver live and stored video services. Limitations Because IPTV requires real-time data transmission and uses the Internet Protocol, it is sensitive to packet loss and delays if the IPTV connection is not fast enough or picture break-up or loss if the streamed data is unreliable. This latter problem has proved particularly troublesome when attempting to stream IPTV across wireless links. Improvements in wireless technology are now starting to provide equipment to solve the problem. ABOUT THE HOME THEATER PC A home theater PC (HTPC) or media PC is a convergence device that combines the functions of a personal computer and a digital video recorder. It is connected to a television or a television-sized computer display and is often used as a digital photo, music, video player, TV receiver and digital video recorder. Home theater PCs are also referred to as media center systems or media servers. The general goal in a HTPC is usually to combine many or all components of a home theater setup into one box. They can be purchased pre-configured with the required hardware and software needed to add television programming to the PC, or can be cobbled together out of discrete components as is commonly done with GB-PVR, SageTV, Famulent or LinuxMCE. HTPC characteristics Beyond functioning as a standard PC, all HTPCs have three additional characteristics in common: * Television connectivity * Quiet / minimal noise during operation * High storage capacities Television connectivity Standard PC units are usually connected to a CRT or LCD display, while HTPCs are designed to be connected to a television. All HTPCs should feature a TV-out option, using either a HDMI, DVI, Component Video, VGA (for some LCD televisions), or S-Video output. Quiet / minimal noise A common user complaint with using standard PCs as HTPC units is background noise, especially in quieter film scenes. Most computers are designed for maximum performance or clock speed, while the functions of a HTPC system may not be processor-intensive. Thus, passive cooling systems, low-speed fans, vibration-absorbing elastic mounts for fans and hard drives, and other minimal noise devices are used in place of conventional cooling systems. Putting the operating system on flash memory and keeping the media on a separate file server elsewhere in the home can eliminate the noise and heat generated by a hard drive. Higher storage capacities Because of the nature of the HTPC, higher than average capacities are required for HTPC units to allow storage of pictures, music, television shows, videos, and other multimedia. Designed almost as a 'permanent storage' device, space can quickly run out on these devices. Because of restrictions on internal space for hard disc drives and a desire for low noise levels, many HTPC units utilise a file server across a network. Some HTPC units also feature a DVD writer to help users copy and move their media. - Comparison with dedicated media devices - Advantages Quality HTPCs may support high-definition television and surround sound. Upsampling DVDs to 720p, or even 1080p/i, for display on a connected HDTV will give a picture that rivals some dedicated home theater equipment. For DVD playback, HTPCs with mid to high end video card technology (Nvidia purevideo or Ati avivo) have defeated standalone DVD players up to the $2000 range in benchmarking tests. Digital video recording Computer-based digital video recorder software that enables the PC to record video from the television signal generally has no monthly subscription fees. The user can schedule recordings from any computer or mobile phone on the Internet. Recording space can easily be upgraded, and/or shows can be burned to DVD or other removable media. These features are also possible with HDTV when using an HDTV tuner card & appropriate software. Premium HDTV channels, which are encrypted, can only be time-shifted with a CableLabs-certified system using an OCUR device under Windows Vista, the same way a TiVo Series 3 can record Premium Content. One media location HTPCs often include online storage of music and movies, usually copied from the original media or downloaded from the Internet onto the HTPC or media server. This allows more convenient access to the content, as well as searching by artist, genre, director, etc. Other common features of a HTPC might include digital photo albums, weather information, news headlines, whole house lighting/appliance control, and the ability to use one remote for all HTPC devices. Gaming Advantages over video game consoles include the ability to play games produced by developers who don't get publishing license with the console manufacturers as well as more connectivity options and customizable input devices. A HTPC can also perform very well as an emulator of console games, allowing the user to store a large library of games designed for a large screen. In addition, computers can usually be built to specifications above that of video game consoles, which means that many PC games will look better than the same game released for a console. However, most HTPCs are not designed with high end gaming in mind, nor are most native commercial PC games designed for large screens. - Disadvantages [ Cost In general, PCs sold as HTPCs tend to be more expensive than ordinary PCs or than dedicated devices as not all PCs include a TV tuner, a remote control, and a flash memory card reader for loading digital photos. It's common to over engineer the hardware slightly so as to keep playback and recording smooth at all times; this increases cost. A special computer case designed to sit near a TV and look like a DVD player may also increase the price, and some of these need smaller motherboards. Setup and maintenance Because HTPCs are far from mainstream, a lot of the commonly used software is not easy for the average computer user to set up. Generally, setting up HTPC software should be done by people who are already very comfortable behind a computer. However, once properly set up, it can be easy to use. Gaming Computer games work on HTPCs, but apart from classics compilations that use software emulators of console or arcade systems, such as Midway Arcade Treasures, few are designed specifically for television displays. Games designed for a generic PC tend to draw text using small fonts that are difficult to read on a standard-definition TV. The majority of generic PC games also tend to allow only one player per machine, and multiplayer gaming requires more than one PC. This makes it difficult to find counterparts to popular party style console games such as Bomberman or the Super Smash Bros. series. Lastly, many HTPCs are normally not built with performance in mind. The graphic adapters equipped on HTPCs may not be top-of-the-line, they may not have the required expansion slots for performance-enhancing expansion cards, and even the motherboard may not be using a chipset that is optimized for performance. As such they do not perform well on games that have a very high hardware specification. Note, however, that most disadvantages presented here apply to pre-fabricated HTPCs sold under that auspice. - Hardware CPU Current generation computer systems have enough computing power to record and play at least one stream of HDTV content, but conservatively, a processor of at least 1GHz will be able to play standard definition TV content even without hardware support. A 2.5Ghz Pentium 4 (roughly a 2Ghz Athlon XP) or faster CPU is needed to play back the highest resolution of HDTV content without dropped frames. TV Capture Several manufacturers build combined TV tuner plus capture cards for PCs. Many such cards offer hardware MPEG encoding to reduce the computing requirements. Some cards are designed for analog TV signals such as standard definition cable or off the air television while others are designed for high definition digital TV. Remote Control Integrating a Media PC into a typical living room requires a way of controlling the computer from a couch across the room. Most wireless keyboards and pointing devices are intended for close range use from a hard surface like a table, but some wireless devices are intended for longer range use. Many TV tuner/capture cards include remote controls for use with the applications included with the card. GB-PVR, SageTV, Media Portal and Beyond TV support the use of a Windows MCE remote control or Snapstream's Firefly remote control. The MCE receiver has 2 IR blaster ports to control set top boxes. Some Directv receivers can be controlled with a serial cable as well. - Software Operating System There are Media PC options available for Windows and Linux users. A common approach for Windows based Media PCs is to install a version of Windows Vista that contains the Windows Media Center(Windows Vista Home Premium or Windows Vista Ultimate) or Windows XP Media Center Edition as the operating system. This release of Windows includes additional software that covers the PVR functions of the Media PC, including free program guide information and automatic program recording. When building your own Windows MCE based Media PC it is worth noting that Windows MCE does not, of itself, provide an MCE certified MPEG2 codec, although one can be purchased from Intel, or is alternatively included when purchasing Intervideo's WinDVD. Other MCE compatible MPEG2 decoders are Nvidia's PureVideo and Sonic's CinePlayer DVD Decoder packages. Alternatively, a Media PC may be built with the addition of a third party software PVR such as GB-PVR, SageTV or Snapstream's BeyondTV to a Windows-equipped PC. SageTV and GB-PVR have integrated placeshifting comparable to the Slingbox, allowing client PCs and the Hauppauge MediaMVP to be connected to the server over the network. Snapstream provides heuristic commercial detection and program recompression. When using a faster CPU, SageTV and Beyond TV can record content from TV capture cards which do not include hardware MPEG2 compression. For a free alternative, GB-PVR and MediaPortal provide full home theatre support and good multi-card DVR capabilities. GB-PVR also has a free client, free mediaMVP client, and free network media playback. For the Linux operating system, KnoppMyth combines the Knoppix Linux distribution with MythTV, a Linux based software PVR, while LinuxMCE combines MythTV and the Kubuntu distribution. SageTV provides commercially supported Linux Media PC software that is compatible with most major Linux distributions. ABOUT VIDEO PROJECTORS A video projector takes a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. Video projectors are widely used for conference room presentations, classroom training, and home theatre applications. A video projector may also be built into a cabinet with a rear-projection screen (rear-projection TV, or RPTV) to form a single unified display device, now popular for “home theater” applications. Common display resolutions for a portable projector include SVGA (800×600 pixels), XGA (1024×768 pixels), 720p (1280×720 pixels), and 1080p (1920×1080 pixels). The cost of a device is not only determined by its resolution, but also by its light output, acoustic noise output, contrast, and other characteristics. While most modern projectors provide sufficient light for a small screen at night or under controlled lighting such as in a basement with no windows[1], a projector with a higher light output (measured in lumens, abbreviated “lm”) is required for a larger screen or a room with a higher amount of ambient light. A rating of 1000 to 1500 ANSI lumens or lower is suitable for smaller screens with controlled lighting or low ambient light.[1][2] Between 1500 and 3000 lm is suitable for medium-sized screens with some ambient light or dimmed light. Over 3000 lm is appropriate for very large screens in a large room with no lighting control (for example, a conference room). Projected image size is important; because the total amount of light does not change, as size increases, brightness decreases. Image sizes are typically measured in linear terms, diagonally, obscuring the fact that larger images require much more light (proportional to the image area, not just the length of a side). Increasing the diagonal measure of the image by 25 % reduces the image brightness by 35 %; an increase of 41 % reduces brightness by half. Projection technologies CRT projector using cathode ray tubes. This typically involves a blue, a green, and a red tube. Minimal maintenance is required (unlike projectors that use expensive lamps which must be periodically replaced after they burn out). This is the oldest system and falling out of favor largely because of the bulky cabinet. However, it does provide the largest screen size for a given cost. This also covers three tube home models, which, while bulky, can be moved. LCD projector using LCD light gates. This is the simplest system, making it one of the most common and affordable for home theaters and business use. Its most common problem is a visible “screen door” or pixelation effect, although recent advances have minimized this. DLP projector using Texas Instruments’ DLP technology. This uses one, two, or three microfabricated light valves called digital micromirror devices (DMDs). The single- and double-DMD versions use rotating color wheels in time with the mirror refreshes to modulate color. The most common problem with the single- or two-DMD varieties is a visible “rainbow” which some people perceive when moving their eyes. Systems with 3 DMDs never have this problem. More recent projectors with higher speed (2x or 4x) and otherwise optimised color wheels have minimized this artifact. LCOS projector using Liquid crystal on silicon. D-ILA JVC’s Direct-drive Image Light Amplifier based on LCOS technology. LED Use an array of Light Emmitting Diodes as the light source, negating the need for lamp replacement. A LASER VIDEO projector takes a video signal and modulates a laser beam in order to project a raster-based image. The systems work either by scanning the entire picture a dot at a time and modulating the laser directly at high frequency, much like the electron beams in a CRT, or by optically spreading and then modulating the laser and scanning a line at a time, the line itself being modulated in much the same way as in a DLP. When well implemented this technology produces the broadest color gamut available in practical display equipment today, derived from the fact that lasers produce truly monochromatic primaries. Due to the special features of laser projectors it is possible to project images or data on any kind of projection surface. Typically sharpness, colour space and contrast are higher than that of other projection technologies (on – off contrast is typically 50,000:1 and higher). In comparison to conventional projectors laser projectors provide a lower luminous flux output, but because of the extremely high contrast, the brightness appears greater.