NICAM

from Wikipedia, the free encyclopedia

NICAM stands for Near Instantaneous Companded Audio Multiplex ('almost immediately compressed sound multiplex') and describes the digital transmission of two audio channels in analog television. The procedure is specified as ETS EN 300 163.

The sound is PCM -coded with 14 bit at 32 kHz sampling frequency .

history

NICAM was developed by the BBC in the 1980s and has been used in the UK for broadcasting stereo broadcasts since 1986 . The transmission method is used by many broadcasters with PAL B / G, I and D / K worldwide, for example in the Nordic countries , Benelux , Spain , Israel , Hong Kong and New Zealand . In Germany, Austria and Switzerland the two-channel sound technique (also called A2 technique) is used.

technology

The NICAM signal is transmitted as a separate subcarrier, regardless of the mono audio carrier signal used (5.85 MHz for System B / G or 6.552 MHz for System I). This means that up to three completely independent audio signals can be transmitted: the conventional mono signal and the two channels of the NICAM signal.

The transmitter shows the content of the two NICAM channels via a control field:

  • a stereo sound channel
  • two mono audio channels (e.g. different languages)
  • a mono audio channel and a 352 kbit / s data channel
  • a 704 kbit / s data channel

The sound is digitized with 14 bits at 32 kHz . This means that the frequency range is limited to 15 kHz. The data of a packet of 32 samples (corresponding to one millisecond) is scaled to 10 bits per sample and provided with a common area information of 3 bits.

The data compiled in this way are packed together with control and parity information in a 728-bit long frame (hence the full name NICAM 728) and sent QPSK- modulated.

See also

Web links

Individual evidence

  1. ↑ ETSI ETS EN 300 163, (previously: EBU T 3266)
  2. ↑ Handbook of Tonstudiotechnik, Volume 1, KG Saur Verlag, 7th edition, Munich 2008, page 651 , ISBN 978-3-598-11765-7 , also from Google books, accessed on March 25, 2020.
  3. ↑ a b Overview of the television standards used worldwide (English) ( Memento from December 5, 2010 in the Internet Archive )
  4. ↑ Steven Hosgood: All You Ever Wanted to Know About NICAM but were Afraid to Ask , 1995–1997, archived September 18, 2010