FIPS 137

FIPS 137, originally issued as FED-STD-1015, is a secure telephony speech encoding standard for Linear Predictive Coding vocoder developed by the United States Department of Defense and finished on November 28th, 1984.[1] It was based on the earlier STANAG 4198[2] promulgated by NATO on February 13th, 1984.

FED-STD-1015 was re-designated as Federal Information Processing Standard (FIPS) Publication 137, (FIPS PUB 137) on October 20th, 1988.[3]

It is also known as "LPC-10".

The codec uses a bit rate of 2.4 kbit/s, requiring 20 MIPS of processing power, 2 kilobytes of RAM and features a frame size of 22.5 ms. Additionally, the codec requires a large lookahead of 90 ms.

Recently an improved version of the standard was introduced. With a longer super frame structure and better VQ quantizer, the bit rate is reduced to 800 bit/s.[4]

References
  1. "FIPS PUB 137, Analog to Digital Conversion of Voice by 2,400 Bit/Second Linear Predictive Coding" (PDF). National Institute of Standards and Technology. Retrieved 2018-08-17.
  2. "PARAMETERS AND CODING CHARACTERISTICS THAT MUST BE COMMON TO ASSURE INTEROPERABILITY OF 2400 BPS LINEAR PREDICTIVE ENCODED DIGITAL SPEECH". North Atlantic Treaty Organization. Retrieved 2018-08-17.
  3. 53 FR 41221
  4. Xianglin, Wang; C.-C. Jay Kuo (May 1998). "An 800 bit/s VQ-based LPC voice coder". The Journal of the Acoustical Society of America. 103 (5): 2778. Bibcode:1998ASAJ..103.2778W. doi:10.1121/1.422247. Archived from the original on 2013-02-23. Retrieved 2007-03-24.


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