Conversion Systems-The Whole Story

How did we get ourselves into this mess/why do different TV standards exist?

We got here as a result of a cocktail of historical developments, vested interests and a healthy dose of nationalist politics... The engineering reasons are lost in the mists of time, but this is where it all started.

TV sets work by displaying a number of pictures in quick succession on the screen. In the early days of television it was deemed A Good Thing if the number of frames per second were simply related to the AC power frequency. Unfortunately two AC mains frequencies are used in the world, 50 and 60 Hz, which immediately divided the world into two camps.

As technology improved it was no longer necessary to keep this relationship between the number of frames per second and the mains frequency - when the Americans introduced color they changed their frame frequency to 59.94 Hz while the mains frequency remained at 60Hz. Nevertheless, the world remains divided into countries that use 60 frames per second, primarily the USA and Japan, and those that have 50 frames per second, which is nearly everyone else. There is a corresponding difference in the number of horizontal lines which make up the picture - 60Hz systems tend to use 525 lines, and 50Hz systems use 625 lines.

The difference in the frame rate is the biggest incompatibility between standards, and is also the hardest to solve.

from bad to worse...

The introduction of colour was a new opportunity to create further divisions. The Americans were first to develop a colour standard, with a system developed by the National Television Standards Committee. Though capable of good results in a closed environment it could exhibit hue variations in a broadcast system, so not one but two incompatible methods of improving things were devised, PAL and SECAM.

Amongst the countries based on 50Hz systems, PAL has been the most widely adopted. PAL is not the only colour system in widespread use with 50Hz; the French designed a system of their own - primarily for political reasons to protect their domestic manufacturing companies - which is known as SECAM, standing for SEquential Couleur Avec Memoire. SECAM was widely adopted in Eastern Block countries to encourage incompatibility with Western transmissions - again a political motive. SECAM is further split between several variants.

Video Systems of The World

DVD Regions:

1: U.S., Canada, U.S. Territories
2: Japan, Europe, South Africa, and Middle East (including Egypt)
3: Southeast Asia and East Asia (including Hong Kong)
4: Australia, New Zealand, Pacific Islands, Central America, Mexico, South America, and the Caribbean
5: Eastern Europe (Former Soviet Union), Indian subcontinent, Africa, North Korea, and Mongolia
6: China
7: Reserved
8: Special international venues (airplanes, cruise ships, etc.)

0: Multiregion

Worldwide Standards For Digital Television

Lastly, you would think that the Worldwide implementation of Digital TV and HDTV would solve the issue of incompatible video systems, but that is not the case. There is a "world" of controversy surrounding the adoption of a universal standard for digital television broadcasting. The US and several North American and Asian countries have adopted the ATSC (Advanced Television Standards Committee standard, Europe has adopted the DVB (Digital Video Broadcasting) standard, and Japan is opting for its own system, ISDB (Integrated Services Digital Broadcasting) . For additional information on the state of Worldwide Digital TV/HDTV standards, check out reports from EE Times and Wikipedia. Leaving out all the technical jargon regarding the various types of Digital/HDTV broadcast standards, this means, in terms of broadcast, cable, and satellite television in the digital age, there will still be incompatibility between the world's nations.

Info collected thanks to:

http://www.centralhome.com/BALLROOMCOUNTRY/video_formats.htm

http://www.anima.demon.co.uk/pvs/faqwhystc.html

http://www.high-techproductions.com/pal,ntsc.htm

http://hometheater.about.com/cs/consumerresources/a/aawhosyourpala_3.htm

http://hometheaterinfo.com/dvd3.htm