IPTV

IPTV (Internet Protocol Television) is a system where a digital television service is delivered using the Internet Protocol over a network infrastructure, which may include delivery by a broadband connection.

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 a Triple Play. Adding the mobile voice service leads to the Quadruple Play denomination. IPTV is typically supplied by a broadband operator using a closed network infrastructure. This closed network approach is in competition with the delivery of TV content over the public Internet. This type of delivery is widely called TV over Internet or Internet Television.

In businesses, IPTV may be used to deliver television content over corporate LANs and business networks. Perhaps a simpler definition of IPTV would be television content that, instead of being delivered through traditional formats and cabling, is received by the viewer through the technologies used for computer networks.

DTV

Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to analog signals 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.

Digital television has several advantages over traditional analog TV, the most significant being that digital channels take up less bandwidth space. This means that digital broadcasters can provide more digital channels in the same space, provide High-Definition digital service, or provide other non-television services such as pay-multimedia services or interactive services. Digital television also permits special services such as multicasting (more than one program on the same channel) and electronic program guides. The sale of non-television services may provide an additional revenue source. As well, digital television often has a superior image, improved audio quality, and better reception than analog.

However, digital television picture technology is still in its early stages. Digital television images have some picture defects that are not present on analog television or motion picture cinema, due to present-day limitations of bandwidth and the compression algorithms such as MPEG-2. When a compressed digital image is compared with the original program source, such as a 35mm motion-picture film print, some digital image sequences may have distortion or degradation such as quantization noise, incorrect color, blockiness when high-speed motion is depicted, or a blurred, shimmering haze.

Video On Demand

Video on demand (VOD) systems allow users to select and watch video content over a network as part of an interactive television system. VOD systems either "stream" content, allowing viewing in real time, or "download" it in which the program is brought in its entirety to a set-top box before viewing starts. The latter is more appropriately termed "store and forward". The majority of cable and telco based VOD systems use the streaming approach, whereby a user buys or selects a movie or television program and it begins to play on the television set almost instantaneously.