View source for FIPS 137

{{Short description|Telephony speech encoding standard}}
'''FIPS 137''', originally issued as '''FED-STD-1015''', is a [[Secure telephone|secure telephony]] [[speech encoding]] standard for [[Linear predictive coding|Linear Predictive Coding]] [[vocoder]] developed by the [[United States Department of Defense]] and finished on November 28, 1984.<ref>{{cite web
| url = https://ptabdata.blob.core.windows.net/files/2017/IPR2017-01077/v23_Exhibit%201022%20-%20FS1015-LPC10.pdf
| title = FIPS PUB 137, Analog to Digital Conversion of Voice by 2,400 Bit/Second Linear Predictive Coding.
| publisher = National Institute of Standards and Technology
| access-date = 2018-08-17
}}</ref>
It was based on the earlier STANAG 4198<ref>{{cite web
| url = http://nso.nato.int/nso/
| title = PARAMETERS AND CODING CHARACTERISTICS THAT MUST BE COMMON TO ASSURE INTEROPERABILITY OF 2400 BPS LINEAR PREDICTIVE ENCODED DIGITAL SPEECH
| publisher = North Atlantic Treaty Organization
| access-date = 2018-08-17
}}</ref> promulgated by [[NATO]] on February 13, 1984.
FED-STD-1015 was re-designated as '''''Federal Information Processing Standard''''' ('''[[Federal Information Processing Standards|FIPS]]''') Publication 137, (FIPS PUB 137) on October 20, 1988.<ref>{{Federal Register|53|41221}}</ref>
It is also known as "LPC-10".
The [[codec]] uses a bit rate of 2.4&nbsp;kbit/s, requiring 20 [[instructions per second|MIPS]] of processing power, 2 kilobytes of [[random access memory|RAM]] and features a frame size of 22.5 ms. Additionally, the codec requires a large [[Dynamic range compression#Look-ahead|lookahead]] of 90 ms.
In 1998, an improved version{{According to whom|date=December 2020}} of the standard was introduced. With a longer super frame structure and better [[Vector quantization|VQ]] quantizer, the [[bit rate]] is reduced to 800 bit/s.<ref>{{cite journal
| last = Xianglin
| first = Wang
| author2 = C.-C. Jay Kuo
| author2-link = C.-C. Jay Kuo
| date = May 1998
| title = An 800 bit/s VQ-based LPC voice coder
| journal = The Journal of the Acoustical Society of America
| volume = 103
| issue = 5
| pages = 2778
| doi = 10.1121/1.422247
| bibcode = 1998ASAJ..103.2778W
| s2cid = 14294667
| url = http://link.aip.org/link/?JASMAN/103/2778/1
| accessdate = 2007-03-24
| archive-url = https://archive.today/20130223071802/http://link.aip.org/link/?JASMAN/103/2778/1
| archive-date = 2013-02-23
| url-status = dead
}}</ref>{{Unreliable source?|date=December 2020}}
==References==
{{Reflist}}
==External links==
* [http://www.speech.cs.cmu.edu/comp.speech/Section3/Software/celp-3.2a.html CELP-3.2a and LPC-10] {{Webarchive|url=https://web.archive.org/web/20161212000335/http://www.speech.cs.cmu.edu/comp.speech/Section3/Software/celp-3.2a.html |date=2016-12-12 }}
* [http://www.speech.cs.cmu.edu/comp.speech/Section3/speechlinks.html Various Speech Coding Links] {{Webarchive|url=https://web.archive.org/web/20161204174554/http://www.speech.cs.cmu.edu/comp.speech/Section3/speechlinks.html |date=2016-12-04 }}
* [http://frc.gatech.edu/wp-content/uploads/sites/578/2004/05/Bae-LPC10.ppt  LPC10 presentation, Soo Hyun Bae, ECE 8873 Data Compression & Modeling, Georgia Institute of Technology, 2004]
[[Category:Speech codecs]]
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