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FS-1015 is a secure telephony speech encoding standard developed by the United States Department of Defense and later by NATO. It is also known as LPC-10 and STANAG 4198.

The standard was finished in 1984. The algorithm used is a linear predictive coding vocoder. The vocoder enables understandable speech, but the quality is very unnatural and synthetic.

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 quantizer, the bit rate is reduced to 800 bit/s.[1]


  1. ^ 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. doi:10.1121/1.422247. Retrieved 2007-03-24. 

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