Archive for category Digital TV
The 2012 London Olympics really brought home to me just what a massive technological jump in digital media has occurred during the last few years. There has been significant advances in digital compression and transmission.
This year, in addition to high definition broadcast, which made its appearance in the 2008 Beijing games, 3D television was also added to the line up, offering more channels and choices. With analogue television broadcast almost becoming extinct, digital televisions promise of delivering more for less has become a reality. Now, how did we arrive at this point and what does the future hold for digital multimedia?
Prior to the digital switchover, analogue television was resource hungry in terms of the amount of bandwidth required to carry a single channel. This is typically between 6 – 8 MHz depending on the type of video standard being used. This limited the number of channels which could be transmitted, since there is a finite amount of spectrum that must be shared with other services such as mobile, radio and two way communications.
What the digital standards of ATSC (North America) and DVB (Rest of the World) provided was the ability to reuse the existing analogue spectrum more efficiently. This meant a typical 8 MHz carrier used for analogue broadcast could be converted to DVB-T (Digital Video – Terrestrial) making it possible to carry 9 standard definition channels or 3 HD channels plus one SD channel for the same amount of bandwidth.
It would have required in excess of 70 MHz of frequency spectrum to achieve this with the old analogue standard. In addition to squeezing more channels into less space, digital television is much clearer and doesn’t suffer from ghosting or other artifacts which troubled analogue systems. Being digital also allows other features like improved digital sound, electronic program guide and subtitle support to be included.
Televisions are sold with the digital decoder integrated and older televisions can use a separate set top box. As technology advances, we will also see improvements in the compression techniques used, which means even more content for digital media, already this has enabled 3D broadcasts for some events such as the Olympics.
Eventually as fibre to the home is deployed worldwide, the all IP enabled set top box will replace the DVB standard, since the IP set top box has a distinct advantage over digital broadcast technologies, specifically multicast join requests. Unlike DVB-T or DVB-S, IP multicast allows the receiver to send a join message to the network for the desired channel then if the request is successful the broadcast is routed to the receiver, only the bandwidth for the requested channel is used. With the DVB standard, all available channels are being broadcast simultaneously, and the channel count is limited by the finite amount of channel bandwidth regardless of the compression techniques being used.
The IP set top box can support both selective multicast (one to many) and on demand unicast (one to one) broadcast, this allows for virtually unlimited amount of content. However, unlike DVB, IP set top boxes have to worry about latency and QOS, since there is traffic contention with both residential broadband and IP Telephony. A poorly implemented IPTV deployment can behave like analogue television in an over subscribed service provider network, unless the correct traffic management is in place. Read the rest of this entry »
Whether you want to watch digital television on your computer or on your analog television you will need a way to receive digital broadcasts. While a lot of people are unhappy about their analog TVs not working there is a solution. Digital TV receivers can be purchased and enable analog televisions to receive digital broadcasts.
Many manufacturers produce digital TV receivers making them widely available. You can buy one from most electrical stores and a number of online stores. For analog TV users, a digital receiver will convert digital signals so that you may watch them on your TV. A digital receiver isn’t just designed for people who have analog TVs.
They can also be used on new TVs for those without access to a digital broadcast. An indoor digital antenna can receive digital signals directly and can be highly practical. Its portability makes it good for virtually anywhere, for example in a caravan or for a student living on a campus.
They are easily installed and don’t require a professional to setup. The only problem that you may encounter is the inability to use your TV remote if you have an analog TV. Since the digital TV receiver does the receiving and converting, the channel is changed via the digital box. For digital TV users, this should not be a problem.
Before you rush out and buy a receiver for your analog TV check that you don’t already have capability to watch digital channels. There are a few circumstances that make a digital TV receiver unnecessary. People with satellite or cable TV will already have the ability to watch digital telly.
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