Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Digital Television shopping experience:

1. Compare - without doubt the biggest advantage that the Digital Television offers shoppers today is the ability to compare thousands of Digital Television at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Digital Television? Wrong! If the Digital Television is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Digital Television then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Digital Television? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Digital Television and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Digital Television wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Digital Television then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Digital Television site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Digital Television, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Digital Television, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to Analog television used by analog (traditional) TV. DTV uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set, or a standard receiver with a set-top box, or a PC fitted with a television card. Introduced in the late 1990s, this technology appealed to the television broadcasting business and consumer electronics industries as offering new financial opportunities.

Technical information Formats and bandwidth In current practice, high-definition television (HDTV), which is usually used over DTV, uses one of two formats: 1280 × 720 pixels in progressive scan mode (abbreviated 720p) or 1920 × 1080 pixels in interlace mode (1080i). Each of these utilizes a 16:9 aspect ratio. (Some televisions are capable of receiving an HD resolution of 1920 × 1080 at a 60Hz progressive scan frame rate — known as 1080p60 — but this format is not standard and no broadcaster is able to transmit these signals over the air at acceptable quality yet.)

Standard definition TV, by comparison, may use one of several different formats taking the form of various aspect ratios, depending on the technology used in the country of broadcast. For 4:3 aspect-ratio broadcasts, the 640 × 480 format is used in NTSC countries, while 704 × 576 (rescaled to 768 × 576) is used in PAL countries. For 16:9 broadcasts, the 704 × 480 (rescaled to 848 × 480) format is used in NTSC countries, while 704 × 576 (rescaled to 1024 × 576) is used in PAL countries. A broadcaster may opt to use a standard-definition digital signal instead of an HDTV signal, because current convention allows the bandwidth of a DTV channel (or "multiplex (TV)") to be subdivided into multiple digital subchannel, providing multiple feeds of entirely different programming on the same channel.

This ability to provide either a single HDTV feed or multiple lower-resolution feeds is often referred to as distributing one's "bit budget" or multicasting. This can sometimes be arranged automatically, using a statistical multiplexer (or "stat-mux"). With some implementations, image resolution may be less directly limited by bandwidth; for in DVB-T, broadcasters can choose from several different modulation schemes, giving them the option to reduce the transmission bitrate and make reception easier for more distant or mobile viewers.

Reception There are a number of different ways to receive digital television. One of the oldest means of receiving DTV (and TV in general) is using an antenna (radio) (known as an aerial in some countries). This way is known as Digital terrestrial television (DTT). With DTT, viewers are limited to whatever channels the antenna picks up. Signal quality will also vary.

Other ways have been devised to receive digital television. Among the most familiar to people are digital cable and digital satellite. In some countries where transmissions of TV signals are normally achieved by microwaves, digital MMDS is used. Other standards, such as Digital multimedia broadcasting and DVB-H, have been devised to allow handheld devices such as mobile phones to receive TV signals. Another way is IPTV, that is receiving TV via Internet Protocol with guaranteed quality of service (QoS). Finally, an alternative way is to receive TV signals via the open Internet infra-structure, usually referred to as Internet TV.

Today, regardless of how viewers receive DTV, most will pick up digital television via a set-top box, which decoder the digital signals into signals that analog televisions can understand — thus using the television purely as a monitor. However, a growing number of TV sets with integrated receivers are available — these are known as iDTVs.

Some signals carry encryption and specify use conditions (such as "may not be recorded" or "may not be viewed on displays larger than 1m in diagonal measure") backed up with the force of law under the WIPO Copyright Treaty and national legislation implementing it, such as the U.S. Digital Millennium Copyright Act. Access to encrypted channels can be controlled by a removable smart card, for example via the Common Interface (DVB-CI) standard for Europe and via Point Of Deployment (POD) for IS or named differently CableCard.

Protection parameters for terrestrial DTV broadcasting {| class="wikitable"|-! System Parameters
(protection ratios)! Canada ! USA ! EBU 12
ITU-mode M3! Japan 37ISDB-T (6MHz, 64QAM, R=2/3), Analog TV (M/NTSC).
|-! C/N for AWGN Channel| +19.5 dB
(16.5 dBThe Canadian parameter, C/(N+I) of noise plus co-channel DTV interface should be 16.5 dB.
)| +15.19 dB| +19.3 dB| +19.2 dB|-! Co-Channel DTV into Analog TV| +33.8 dB| +34.44 dB| +34 ~ 37 dB| +38 dB|-! Co-Channel Analog TV into DTV| +7.2 dB| +1.81 dB| +4 dB| +4 dB|-! Co-Channel DTV into DTV| +19.5 dB
(16.5 dB)| +15.27 dB| +19 dB| +19 dB|-! Lower Adjacent Channel DTV into Analog TV| −16 dB| −17.43 dB| −5 ~ −11 dBDepending on analog TV systems used.| −6 dB|-! Upper Adjacent Channel DTV into Analog TV| −12 dB| −11.95 dB| −1 ~ −10| −5 dB|-! Lower Adjacent Channel Analog TV into DTV| −48 dB| −47.33 dB| −34 ~ −37 dB| −35 dB|-! Upper Adjacent Channel Analog TV into DTV| −49 dB| −48.71 dB| −38 ~ −36 dB| −37 dB|-! Lower Adjacent Channel DTV into DTV| −27 dB| −28 dB| −30 dB| −28 dB|-! Upper Adjacent Channel DTV into DTV| −27 dB| −26 dB| −30 dB| −29 dB|}

Interaction Interaction happens between the TV watcher and the DTV system. It can be understood in different ways, depending on which part of the DTV system is concerned. It can be an interaction with the STB only (to tune to another TV channel or to browse the Electronic program guide).

Modern DTV systems are able to provide interaction between the end-user and the broadcaster through the use of a return path. With the exceptions of coaxial and fiber optic cable, which can be bidirectional, a dialup modem, Internet connection, or other method is typically used for the return path with unidirectional networks such as satellite or antenna broadcast.

In addition to not needing a separate return path, cable also has the advantage of a communication channel localized to a neighborhood rather than a city (terrestrial) or an even larger area (satellite). This provides enough customizable bandwidth to allow true video on demand.

Analog switch-off Many countries around the world currently operate a simulcast service where a broadcast is made available to viewers in both analog and digital at the same time. As digital becomes more popular it is likely that the existing analog services will be removed. In some cases this has already happened where a broadcaster has offered incentives to viewers to encourage them to switch to digital or simply switched their service regardless of whether they want to switch. In other cases government policies have been introduced to encourage the switch-over process, especially with regard to terrestrial broadcasts.

Government intervention usually involves providing some funding for broadcasters to enable a switch-over to happen by a given deadline.

Switch-off completed

Switch-off in progress

Switch-off time announced

The analog switch-off ruling, which so far has met with little opposition from consumers or manufacturers, would render all non-digital televisions dark and obsolete on the switch-off date, unless connected to an external off-the-air tuner, analog or digital cable, or a satellite system. The FCC has determined that an external tuning device can simply be added to non-digital televisions to lengthen their useful lifespan. Several of these devices have already been shown, and it is expected that low-cost units will be available in January 2008. At that same time, the U.S. government will take requests from households for up to two coupons to reduce the price of some converter boxes by $40. Currently, even the earliest televisions continue to work with present broadcast standards. This mandate was designed to help provide a painless transition to the new standard.

Pros and cons DTV has several advantages over traditional, analog TV, the most significant being that digital channels take up less bandwidth (and the bandwidth needs are continuously variable, at a corresponding cost in image quality depending on the level of compression). This means that digital broadcasters can provide more digital channels in the same space, provide High-definition television service, or provide other non-television services such as multimedia or interactivity. DTV also permits special services such as multiplexing (more than one program on the same channel), electronic program guides and additional languages, spoken or subtitled. The sale of non-television services may provide an additional revenue source. In many cases, viewers perceive DTV to have superior picture quality, improved audio quality, and easier reception than analog.

However, DTV picture technology is still in its early stages. DTV images have some picture defects that are not present on analog television or motion picture cinema, due to present-day limitations of bandwidth and compression algorithms such as MPEG-2.

When a compressed digital image is compared with the original program source, some hard-to-compress image sequences may have digital distortion or degradation. For example:

Broadcasters attempt to balance their needs to show high quality pictures and to generate revenue by using a fixed bandwidth allocation for more services.

See also

References External links

Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to Analog television used by analog (traditional) TV. DTV uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set, or a standard receiver with a set-top box, or a PC fitted with a television card. Introduced in the late 1990s, this technology appealed to the television broadcasting business and consumer electronics industries as offering new financial opportunities.

Technical information Formats and bandwidth In current practice, high-definition television (HDTV), which is usually used over DTV, uses one of two formats: 1280 × 720 pixels in progressive scan mode (abbreviated 720p) or 1920 × 1080 pixels in interlace mode (1080i). Each of these utilizes a 16:9 aspect ratio. (Some televisions are capable of receiving an HD resolution of 1920 × 1080 at a 60Hz progressive scan frame rate — known as 1080p60 — but this format is not standard and no broadcaster is able to transmit these signals over the air at acceptable quality yet.)

Standard definition TV, by comparison, may use one of several different formats taking the form of various aspect ratios, depending on the technology used in the country of broadcast. For 4:3 aspect-ratio broadcasts, the 640 × 480 format is used in NTSC countries, while 704 × 576 (rescaled to 768 × 576) is used in PAL countries. For 16:9 broadcasts, the 704 × 480 (rescaled to 848 × 480) format is used in NTSC countries, while 704 × 576 (rescaled to 1024 × 576) is used in PAL countries. A broadcaster may opt to use a standard-definition digital signal instead of an HDTV signal, because current convention allows the bandwidth of a DTV channel (or "multiplex (TV)") to be subdivided into multiple digital subchannel, providing multiple feeds of entirely different programming on the same channel.

This ability to provide either a single HDTV feed or multiple lower-resolution feeds is often referred to as distributing one's "bit budget" or multicasting. This can sometimes be arranged automatically, using a statistical multiplexer (or "stat-mux"). With some implementations, image resolution may be less directly limited by bandwidth; for in DVB-T, broadcasters can choose from several different modulation schemes, giving them the option to reduce the transmission bitrate and make reception easier for more distant or mobile viewers.

Reception There are a number of different ways to receive digital television. One of the oldest means of receiving DTV (and TV in general) is using an antenna (radio) (known as an aerial in some countries). This way is known as Digital terrestrial television (DTT). With DTT, viewers are limited to whatever channels the antenna picks up. Signal quality will also vary.

Other ways have been devised to receive digital television. Among the most familiar to people are digital cable and digital satellite. In some countries where transmissions of TV signals are normally achieved by microwaves, digital MMDS is used. Other standards, such as Digital multimedia broadcasting and DVB-H, have been devised to allow handheld devices such as mobile phones to receive TV signals. Another way is IPTV, that is receiving TV via Internet Protocol with guaranteed quality of service (QoS). Finally, an alternative way is to receive TV signals via the open Internet infra-structure, usually referred to as Internet TV.

Today, regardless of how viewers receive DTV, most will pick up digital television via a set-top box, which decoder the digital signals into signals that analog televisions can understand — thus using the television purely as a monitor. However, a growing number of TV sets with integrated receivers are available — these are known as iDTVs.

Some signals carry encryption and specify use conditions (such as "may not be recorded" or "may not be viewed on displays larger than 1m in diagonal measure") backed up with the force of law under the WIPO Copyright Treaty and national legislation implementing it, such as the U.S. Digital Millennium Copyright Act. Access to encrypted channels can be controlled by a removable smart card, for example via the Common Interface (DVB-CI) standard for Europe and via Point Of Deployment (POD) for IS or named differently CableCard.

Protection parameters for terrestrial DTV broadcasting {| class="wikitable"|-! System Parameters
(protection ratios)! Canada ! USA ! EBU 12
ITU-mode M3! Japan 37ISDB-T (6MHz, 64QAM, R=2/3), Analog TV (M/NTSC).
|-! C/N for AWGN Channel| +19.5 dB
(16.5 dBThe Canadian parameter, C/(N+I) of noise plus co-channel DTV interface should be 16.5 dB.
)| +15.19 dB| +19.3 dB| +19.2 dB|-! Co-Channel DTV into Analog TV| +33.8 dB| +34.44 dB| +34 ~ 37 dB| +38 dB|-! Co-Channel Analog TV into DTV| +7.2 dB| +1.81 dB| +4 dB| +4 dB|-! Co-Channel DTV into DTV| +19.5 dB
(16.5 dB)| +15.27 dB| +19 dB| +19 dB|-! Lower Adjacent Channel DTV into Analog TV| −16 dB| −17.43 dB| −5 ~ −11 dBDepending on analog TV systems used.| −6 dB|-! Upper Adjacent Channel DTV into Analog TV| −12 dB| −11.95 dB| −1 ~ −10| −5 dB|-! Lower Adjacent Channel Analog TV into DTV| −48 dB| −47.33 dB| −34 ~ −37 dB| −35 dB|-! Upper Adjacent Channel Analog TV into DTV| −49 dB| −48.71 dB| −38 ~ −36 dB| −37 dB|-! Lower Adjacent Channel DTV into DTV| −27 dB| −28 dB| −30 dB| −28 dB|-! Upper Adjacent Channel DTV into DTV| −27 dB| −26 dB| −30 dB| −29 dB|}

Interaction Interaction happens between the TV watcher and the DTV system. It can be understood in different ways, depending on which part of the DTV system is concerned. It can be an interaction with the STB only (to tune to another TV channel or to browse the Electronic program guide).

Modern DTV systems are able to provide interaction between the end-user and the broadcaster through the use of a return path. With the exceptions of coaxial and fiber optic cable, which can be bidirectional, a dialup modem, Internet connection, or other method is typically used for the return path with unidirectional networks such as satellite or antenna broadcast.

In addition to not needing a separate return path, cable also has the advantage of a communication channel localized to a neighborhood rather than a city (terrestrial) or an even larger area (satellite). This provides enough customizable bandwidth to allow true video on demand.

Analog switch-off Many countries around the world currently operate a simulcast service where a broadcast is made available to viewers in both analog and digital at the same time. As digital becomes more popular it is likely that the existing analog services will be removed. In some cases this has already happened where a broadcaster has offered incentives to viewers to encourage them to switch to digital or simply switched their service regardless of whether they want to switch. In other cases government policies have been introduced to encourage the switch-over process, especially with regard to terrestrial broadcasts.

Government intervention usually involves providing some funding for broadcasters to enable a switch-over to happen by a given deadline.

Switch-off completed

Switch-off in progress

Switch-off time announced

The analog switch-off ruling, which so far has met with little opposition from consumers or manufacturers, would render all non-digital televisions dark and obsolete on the switch-off date, unless connected to an external off-the-air tuner, analog or digital cable, or a satellite system. The FCC has determined that an external tuning device can simply be added to non-digital televisions to lengthen their useful lifespan. Several of these devices have already been shown, and it is expected that low-cost units will be available in January 2008. At that same time, the U.S. government will take requests from households for up to two coupons to reduce the price of some converter boxes by $40. Currently, even the earliest televisions continue to work with present broadcast standards. This mandate was designed to help provide a painless transition to the new standard.

Pros and cons DTV has several advantages over traditional, analog TV, the most significant being that digital channels take up less bandwidth (and the bandwidth needs are continuously variable, at a corresponding cost in image quality depending on the level of compression). This means that digital broadcasters can provide more digital channels in the same space, provide High-definition television service, or provide other non-television services such as multimedia or interactivity. DTV also permits special services such as multiplexing (more than one program on the same channel), electronic program guides and additional languages, spoken or subtitled. The sale of non-television services may provide an additional revenue source. In many cases, viewers perceive DTV to have superior picture quality, improved audio quality, and easier reception than analog.

However, DTV picture technology is still in its early stages. DTV images have some picture defects that are not present on analog television or motion picture cinema, due to present-day limitations of bandwidth and compression algorithms such as MPEG-2.

When a compressed digital image is compared with the original program source, some hard-to-compress image sequences may have digital distortion or degradation. For example:

Broadcasters attempt to balance their needs to show high quality pictures and to generate revenue by using a fixed bandwidth allocation for more services.

See also

References External links



UK Government Digital Television
UK Government Digital Television Switchover Information ... you are here : home . Between 2008- 2012, television services in the UK will go completely digital, TV region by TV ...

Digital Television - Publications
Publications Homepage, Digital Television Publications Archive ... you are here : home | publications Recent Publications . 14 December 2007 . BERR releases two tender documents ...

Digital TV - Digital Spy
Showbiz, TV, entertainment and media news around the clock. ... Aug 18, 15:02. Lorraine Kelly series to launch Real Lives HD A second series of Lorraine Kelly's DNA Stories will ...

Television - Digital Spy
Showbiz, TV, entertainment and media news around the clock. ... Suranne Jones to star in new ITV thriller. Aug 19, 14:25 - Former Corrie star Suranne Jones is starring in ...

Compare UK Digital TV Packages
Compare digital, cable and satellite TV packages in the UK - read consumer guides and check availability.

Getting set for the Digital TV Switchover Digital UK
Not for profit organisation formed by the broadcasters to assist consumers in the conversion to digital TV. Includes information on tuning, digital switch over, timetables ...

Digital TV - Compare Digital TV Providers Online
Compare Digital TV providers online with Digital TV, find out what digital tv packages are on offer and from whom - with up-to-date information on the digital switchover.

Digital TV Group Web Site Home Page
UK-based industry group of companies devoted to standards for DVB and digital television.

digital television recorders | digital tv products | best set top ...
Digital TV Consumer test reports. This UK Government-funded website is to help consumers choose the equipment needed to switch to digital television

BBC - Digital - TV
Find out what digital tv is all about, what it means for you and how to go digital. ... The BBC is not responsible for the content of external internet sites

 

Digital Television



 
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