Broadcasting System Details

Technical Specifications

Stereo Sound

• MTS - Used in conjunction with NTSC/525. Consists of two independant carriers each carrying a discrete channel. One channel provides stereo sound by providing left/right channel difference signals relative to transmitted mono audio track. The second carrier carries the Secondary Audio Program (SAP) which is used for a second language or a descriptive commentary for the blind. Uses a technique based on the dbx noise reduction to improve the frequency response of the audio channel.
• FM-FM - dual carrier FM coded discrete stereo transmissions, analogue. Can be used for bi-lingual operation under user selection, but no auto-selection is available. Audio characteristics better than standard mono soundtrack.
• NICAM - (full name: NICAM 728) Digital two-channel audio transmissions with sub-code selection of bi-lingual operation. Stereo digital signals with specifications approaching those of Compact Disc are possible. NICAM stands for Near Instantaneously Companded Audio Multiplex and uses a 14bit sample at a 32KHz sampling rate which produces a data stream of 728KBits/sec.

Subtitling

• CC - (full name: Closed Captioning) Transmitted on line 21 of NTSC/525 transmissions, contains subtitling information only. CC has no support for block graphics or multiple pages but it can support 8-colours and the use of an italic typeface. Frequently found on pre-recorded VHS cassettes and LDs, also used on broadcast. Also found on PAL/625 pre-recorded VHS cassettes in a modified version.
• TeleText - An information service of 200-700 "pages" covering a wide range of topics including TV Schedules, News, Financial Market prices, Comment, Reviews, Concert & Theatre information. Subtitles are typically transmitted on page 888 in the UK, on pages 199/299/399 in Belgium and Holland, on page 150 in Germany and on page 777 in Italy. There are a number of variant character sets used, but the encoding is identical and all English alphabet characters plus numbers and most punctuation can be handled by any decoder. Includes support for 8 colours, and limited block graphics, and selective revealing of underlying TV picture. Transmitted on a variable number of lines (specified in header which contains basic information such as time, date and channel), starting on line 12 and continuing for 7-8 lines typically. Found on broadcasts and some LaserDiscs; recording of TeleText signals is marginal on S-VHS, almost impossible on VHS hence the PAL/625 version of CC.

The BBC-designed Teletext system is known in some quarters as World Standard Teletext. There is an enhanced version known as Fastext which defines four links to additional pages that can be followed with one of four coloured buttons on the Teletext receivers remote control. The U.S. "CC" is known widely in technical circles as LITO = LIne Twenty-One! where it lives.

Color and Broadcasting Systems by Country

Provided through the courtesy of Bevis King <B.King@ee.surrey.ac.uk>

To view his original version of this page click here.

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