Signals and Interfaces

Proposed DTV Formats

Current Formats for Standard Definition (DTV) and High Definition (HDTV)

What About 720p ?

Interlace vs. Progressive Scanning

Multipliers and Scalars
Inverse Telecine and 3:2 Pulldown

MPEG Decoding

Component Video
RGB vs Y,P_R,P_B

The idea of digital recording has been around for a long time. The IBA (the forerunner of the ITC-the Independent Television Commission) licensed the first digital tape recorder in the early 1980's. However the first advance in recording was an improved analog system, BetaCam. This was a component analog system where the information was split up into color and luminance, stored on separate tracks. This gave a higher picture quality, but was overtaken in the early 1990's by digital systems, such as DigiBetaCam. These give an even better picture and make editing with on-line computer systems possible (this form of editing makes the process much easier- it can be compared to a word processor whereas previous editing systems were mere typewriters!).

In the television industry the use of DVC and DVD (Digital Video Cassette and Digital Video Disk) are widespread. This means of recording has recently been standardized again. The broadcast industry standard is now MPEG-2 (Motion Picture Experts Group standard 2). This cuts the amount of information from nearly 100 million 'bits' per second to less then 5 million. It does this by not specifying the information for each individual pixel, but rather the boundaries of groups of pixels of the same color and brightness.

Although the use of digital technology in recording television is now quite established the next step is to broadcast the information digitally. This is the 'revolution' which is currently being discussed at length. There are three main ways of transmitting television broadcasts; cable, satellite, and terrestrial (or "over the air"). At the moment the ITC is formulating a technical code of practice for Digital Terrestrial Television. There are six 'multiplexes' available and five of these have already been licensed as follows:

Multiplex 2 Channel 3/4 Digital LTD
Multiplex 3 SDN:S4C Digital Networks Limited
Multiplex 4,5, and 6 BDB:British Digital Broadcasting

The information for these multiplexes can be transmitted in the 'gaps' of a normal analog broadcast, and the information is compressed to such a degree that four, five, or six digital channels can be broadcast in the spaces of one analog one.

As far as the major companies and web sites are concerned there are an overwhelming number of companies supplying equipment such as cameras, many of which have websites, but these are understandably biased towards a particular supplier. The best web site for your purposes is probably the ITC's own, which gives details of the companies who have been licensed and a digital television fact sheet. 

As digital engine based sets such as the DLP and LCD TV's become more common for home theater, it is expected to adopt and convert incoming signals to the 720p format. It is inherently simple to do so when using a display technology based on computing monitors, which are natively progressive.  Many consumer electronics manufacturers have decided to skip the more expensive circuitry required to scan in 720p. 

There has been much debate as to if this standard should be adopted in our television sets, and it is indeed the preference of many videophiles in viewing film based pictures in the progressive mode, where the movement flows smoother with the full frame based image. Currently 720p is found in high-end DLP and LCD engines.