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Vocoder Phone Voice
Linear Predictive Coding
- this page is a stub
Linear Predictive Coding (LPC), also known as LPC-10, FIPS 137 and
FED-STD-1015, is a speech encoding standard,
or vocoder, used in (secure) telephony.
It is a method for digitizing speech by analyzing and storing
specific characteristics of it,
such as pitch and voiced/voiceless sounds,
in such a way that an intelligible
signal can be reconstructed (synthesized) later.
The standard, finished on 28 November 1984, was developed by the
US Department of Defense (DoD) and is based on the
earlier STANAG 4198 standard, promulgated by
NATO on 13 February 1984 [1].
LPC was used with early voice encryption equipment, such as
STU-I, STU-II,
KY-57 (VINSON) and
Spendex 40,
and allows speech compression at low bitrates — typically between 800 and
2400 baud.
LPC-10e is a US Government standard that was even used on
STU-III terminals, when running at 2400 baud.
LPC-10 is an open standard, used and implemented by many manufacturers.
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Name LPC-10 Description Linear Predictive Coding with 10 coefficients Developer NSA Standards FIPS 137, FED-STD-1015 Year 1973 Bandwidth 2400 bps Frame 180 samples, 54 bits, 22.5 ms (i.e. 44.44 frames/sec) Target 8 kHz sampling rate, 16 bit quantisation
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- Linear Predictive Coding
- LPC
- LPC-10
- FIPS 137
- FED-STD-1015
- STANAG 4198
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- GSM
- Shorten
- MPEG-4 ALS
- FLAC
- SILK audio codec
- Military narrowband communication
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1944 Norbert Wiener: Mathematical Theory of Linear Prediction 1947 Claude Shannon: Mathematical Theory of Communication (general) 1952 C. Chapin Cutler, Bernard M. Oliver & Henry C. Harrison:
work on predictive coding 1955 Peter Elias: two papers on predictive coding 1966 Fumitada Itakura (Nagoya University): Linear predictors used in speech analysis 1966 Shuzo Saito (Nippon Telegraph and Telephone):
Linear predictors used in speech analysis 1967 Bishnu S. Atal, Manfred R. Schroeder and John Burg:
Adaptive Linear Predictor approach, Primciple of maximum entropy 1969 Itakura & Saito: Partial Correlation (PARCOR) 1969 Glen Culler: Real-time speech encoding proposal 1969 Bishnu S. Atal: First presentation of LPC speech coder 1971 Philco-Ford: Real-time LPC with 16-bit hardware (demonstration) 1972 Bob Kahn (ARPA) & Jim Forgie (LL) & Dave Walden (BBN):
First developments in packetized speech (later: VoIP) 1973 Ed Hofstetter (LL): first real-time 2400 bps LPC 1973 US Navy: first real-time LPC 1974 First real-time two-way LPC between Culler-Harrison and LL
via ARPANET at 3500 pbs 1978 US Navy becomes technical agent for further LPC development 1978 Atal, Vishwanath et al. (NBN): first variable-rate LPC algorithm 1978 Atal & Schroeder (Bell Labs): LPC codec: Adaptive Predictive Coding 1 1985 Atal & Schroeder: Code-Exited Linear Prediction (CELP)
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Based on masking properties of the hman ear. This later became the
basis for the perceptual coding technique used in MP3 (1993).
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© Crypto Museum. Created: Saturday 03 April 2021. Last changed: Monday, 06 October 2025 - 09:05 CET.
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