FS-1015
Encyclopedia
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 1984. The algorithm used is a linear predictive coding
vocoder
. The vocoder enables understandable speech, but the quality is very unnatural and synthetic. File size is 20 times smaller than MP3 - it is very small.
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 is introduced. With longer super frame structure and better quantizer the bit rate is reduced to 800 bit/s.
Speech encoding
Speech coding is the application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting...
standard developed by the United States Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
and later by NATO. It is also known as LPC-10 and STANAG 4198.
The standard was finished 1984. The algorithm used is a linear predictive coding
Linear predictive coding
Linear predictive coding is a tool used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model...
vocoder
Vocoder
A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...
. The vocoder enables understandable speech, but the quality is very unnatural and synthetic. File size is 20 times smaller than MP3 - it is very small.
The codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
uses a bit rate of 2.4 kbit/s, requiring 20 MIPS
Instructions per second
Instructions per second is a measure of a computer's processor speed. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches, whereas realistic workloads typically lead to significantly lower IPS values...
of processing power, 2 kilobytes of RAM and features a frame size of 22.5 ms. Additionally, the codec requires a large lookahead
Lookahead
Lookahead is a tool in algorithms for looking ahead a few more input items before making a cost effective decision at one stage of the algorithm.- Lookahead in search problems :...
of 90 ms.
Recently an improved version of the standard is introduced. With longer super frame structure and better quantizer the bit rate is reduced to 800 bit/s.