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MELP
Mixed-excitation linear prediction (MELP) is a United States Department of Defense speech coding standard used mainly in military applications and satellite communications, secure voice, and secure radio devices. Its standardization and later development was led and supported by the NSA and NATO. The current "enhanced" version is known as MELPe. History The initial MELP was invented by Alan McCree around 1995 while a graduate student at the Center for Signal and Image Processing (CSIP) at Georgia Tech, and the original MELP related patents have expired by now. That initial speech coder was standardized in 1997 and was known as MIL-STD-3005. It surpassed other candidate vocoders in the US DoD competition, including: (a) Frequency Selective Harmonic Coder (FSHC), (b) Advanced Multi-Band Excitation (AMBE), (c) Enhanced Multiband Excitation (EMBE), (d) Sinusoid Transform Coder (STC), and (e) Subband LPC Coder (SBC). Due to its lower complexity than Waveform Interpolative (WI) coder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secure Voice
Secure voice (alternatively secure speech or ciphony) is a term in cryptography for the encryption of voice communication over a range of communication types such as radio, telephone or IP. History The implementation of voice encryption dates back to World War II when secure communication was paramount to the US armed forces. During that time, noise was simply added to a voice signal to prevent enemies from listening to the conversations. Noise was added by playing a record of noise in sync with the voice signal and when the voice signal reached the receiver, the noise signal was subtracted out, leaving the original voice signal. In order to subtract out the noise, the receiver need to have exactly the same noise signal and the noise records were only made in pairs; one for the transmitter and one for the receiver. Having only two copies of records made it impossible for the wrong receiver to decrypt the signal. To implement the system, the army contracted Bell Laboratori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FS-1016
FS-1016 (also called FED-STD-1016) is a deprecated secure telephony speech encoding standard for Code-excited linear prediction (CELP) developed by the United States Department of Defense and finalized February 14, 1991. Unlike the vocoder used in FS-1015, CELP provides more natural speech. However, due to quite low bit rate and early development (1991), the speech quality is very noisy and below that of commercial cellular speech codec such as AMR. FS-1016 is no longer used since its follow-up MELP provides better performance in all applications. Technical details The bit rate of the codec is 4.8 kbit/s. The complexity of the codec is 19 MIPS. The RAM requirement is 1.5 kilobytes. Frame size of the codec is 30 ms. Look-ahead of 7.5 ms is also required. The variation of CELP Code-excited linear prediction (CELP) is a linear predictive speech coding algorithm originally proposed by Manfred R. Schroeder and Bishnu S. Atal in 1985. At the time, it provided s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FS1016
FS-1016 (also called FED-STD-1016) is a deprecated secure telephony speech encoding standard for Code-excited linear prediction (CELP) developed by the United States Department of Defense and finalized February 14, 1991. Unlike the vocoder used in FS-1015, CELP provides more natural speech. However, due to quite low bit rate and early development (1991), the speech quality is very noisy and below that of commercial cellular speech codec such as AMR. FS-1016 is no longer used since its follow-up MELP provides better performance in all applications. Technical details The bit rate of the codec is 4.8 kbit/s. The complexity of the codec is 19 MIPS. The RAM requirement is 1.5 kilobytes. Frame size of the codec is 30 ms. Look-ahead of 7.5 ms is also required. The variation of CELP Code-excited linear prediction (CELP) is a linear predictive speech coding algorithm originally proposed by Manfred R. Schroeder and Bishnu S. Atal in 1985. At the time, it provided s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
STANAG
In NATO, a standardization agreement (STANAG, redundantly: STANAG agreement) defines processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance. Each NATO state ratifies a STANAG and implements it within its own military. The purpose is to provide common operational and administrative procedures and logistics, so one member nation's military may use the stores and support of another member's military. STANAGs also form the basis for technical interoperability between a wide variety of communication and information systems (CIS) essential for NATO and Allied operations. The Allied Data Publication 34 (ADatP-34) NATO Interoperability Standards and Profiles which is covered by STANAG 5524, maintains a catalogue of relevant information and communication technology standards. STANAGs are published in English and French, the two official languages of NATO, by the NATO Standardization Office in Bru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FS-1015
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 28, 1984. It was based on the earlier STANAG 4198 promulgated by NATO on February 13, 1984. FED-STD-1015 was re-designated as ''Federal Information Processing Standard'' ( FIPS) Publication 137, (FIPS PUB 137) on October 20, 1988. 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 In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LPC-10
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 28, 1984. It was based on the earlier STANAG 4198 promulgated by NATO on February 13, 1984. FED-STD-1015 was re-designated as ''Federal Information Processing Standard'' ( FIPS) Publication 137, (FIPS PUB 137) on October 20, 1988. 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 In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AT&T
AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile telephone services in the U.S. , AT&T was ranked 13th on the ''Fortune'' 500 rankings of the largest United States corporations, with revenues of $168.8 billion. During most of the 20th century, AT&T had a monopoly on phone service in the United States. The company began its history as the American District Telegraph Company, formed in St. Louis in 1878. After expanding services to Arkansas, Kansas, Oklahoma and Texas, through a series of mergers, it became Southwestern Bell Telephone Company in 1920, which was then a subsidiary of American Telephone and Telegraph Company. The latter was a successor of the original Bell Telephone Company founded by Alexander Graham Bell in 1877. The American Bell Telephone Company formed the American Teleph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Texas Instruments
Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globally. It is one of the top 10 semiconductor companies worldwide based on sales volume. The company's focus is on developing analog chips and embedded processors, which account for more than 80% of its revenue. TI also produces TI digital light processing technology and education technology products including calculators, microcontrollers, and multi-core processors. The company holds 45,000 patents worldwide as of 2016. Texas Instruments emerged in 1951 after a reorganization of Geophysical Service Incorporated, a company founded in 1930 that manufactured equipment for use in the seismic industry, as well as defense electronics. TI produced the world's first commercial silicon transistor in 1954, and the same year designed and manufactured t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thales Group
Thales Group () is a French multinational company that designs, develops and manufactures electrical systems as well as devices and equipment for the aerospace, defence, transportation and security sectors. The company is headquartered in Paris' business district, La Défense, and its stock is listed on the Euronext Paris. Having been known as Thomson-CSF since its foundation in 1968, the company was rebranded ''Thales'' (named after the Greek philosopher Thales and pronounced , reflecting its pronunciation in French) in December 2000. A communication audit, launched in spring that year, highlighted Thomson-CSF's image deficit, particularly among the young French graduates it was seeking to recruit. The wish to liven up its image as well as the expansion of its business worldwide were cited among the reasons for the change. Thales is partially owned by the French State and operates in more than 56 countries. It had 80,000 employees and generated €18.4 billion in revenues in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CVSD
Continuously variable slope delta modulation (CVSD or CVSDM) is a voice coding method. It is a delta modulation with variable step size (i.e., special case of adaptive delta modulation), first proposed by Greefkes and Riemens in 1970. CVSD encodes at 1 bit per sample, so that audio sampled at 16 kHz is encoded at 16 kbit/s. The encoder maintains a reference sample and a step size. Each input sample is compared to the reference sample. If the input sample is larger, the encoder emits a ''1'' bit and adds the step size to the reference sample. If the input sample is smaller, the encoder emits a ''0'' bit and subtracts the step size from the reference sample. The encoder also keeps the previous ''N'' bits of output (''N'' = 3 or ''N'' = 4 are very common) to determine adjustments to the step size; if the previous ''N'' bits are all 1s or 0s, the step size is increased. Otherwise, the step size is decreased (usually in an exponential manner, with \tau being in the range ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CELP
Code-excited linear prediction (CELP) is a linear predictive speech coding algorithm originally proposed by Manfred R. Schroeder and Bishnu S. Atal in 1985. At the time, it provided significantly better quality than existing low bit-rate algorithms, such as residual-excited linear prediction (RELP) and linear predictive coding (LPC) vocoders (e.g., FS-1015). Along with its variants, such as algebraic CELP, relaxed CELP, low-delay CELP and vector sum excited linear prediction, it is currently the most widely used speech coding algorithm. It is also used in MPEG-4 Audio speech coding. CELP is commonly used as a generic term for a class of algorithms and not for a particular codec. Background The CELP algorithm is based on four main ideas: * Using the source-filter model of speech production through linear prediction (LP) (see the textbook "speech coding algorithm"); * Using an adaptive and a fixed codebook as the input (excitation) of the LP model; * Performing a search in close ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
