Editing NICAM (section)

==Differing features==
NICAM sampling is not standard [[Pulse-code modulation|PCM]] sampling, as commonly employed with the [[Compact Disc]] or at the codec level in [[MP3]], [[Advanced Audio Coding|AAC]] or [[Ogg]] audio devices. NICAM sampling more closely resembles [[ADPCM|Adaptive Differential Pulse Code Modulation]], or [[A-law]] companding with an extended, rapidly modifiable dynamic range.

===Two's complement signing===
The [[two's complement]] method of signing the samples is used,<ref name="AllYouEverWanted">{{cite web|url=http://stoneship.org.uk/~steve/nicam.html |title=All You Ever Wanted to Know About NICAM but were Afraid to Ask |author=Steve Hosgood |access-date=2007-08-30 |url-status=dead |archive-url=https://web.archive.org/web/20050214130459/http://stoneship.org.uk/~steve/nicam.html |archive-date=February 14, 2005 }}</ref> so that:
* <span style="font-family: monospace;">01111111111111</span> represents positive full-scale
* <span style="font-family: monospace;">10000000000000</span> represents negative full-scale

=== ±0 V has three binary representations ===
* <span style="font-family: monospace;">00000000000001</span> represents 0 V, with no +/- distinction. This may have originated as a method to reduce the emergence of DC patterns from transmission of silent material.
* <span style="font-family: monospace;">00000000000000</span> represents 0 V, with no +/- distinction
* <span style="font-family: monospace;">11111111111111</span> represents 0 V, with no +/- distinction

=== Parity checking limited to only 6 of 10 bits ===
In order to strengthen parity protection for the sound samples, the parity bit is calculated on only the top six bits of each NICAM sample. Early BBC NICAM research showed that uncorrected errors in the least significant four bits were preferable to the reduced overall protection offered by parity-protecting all ten bits.