View source for Milestone-Proposal:Line spectrum pair (LSP), an essential technology for high-compression speech coding, 1975

{{Proposal
|docketid=2012-07
|more than 25 years=Yes
|within fields of interest=Yes
|benefit to humanity=Yes
|regional importance=Yes
|ou is paying=Yes
|ou is arranging dedication=Yes
|section is taking responsibility for plaque=Yes
|a11=Yes
|a3=1975
|a1=Line spectrum pair (LSP), an essential technology for high-compression speech coding, 1975
|plaque citation=LSP (Line Spectrum Pair), invented at NTT in 1975, is a key technology for speech coding. A speech synthesizer LSI was designed based on LSP in 1980, and many international speech coding standards of ITU-T, 3GPP, 3GPP2, and IETF have adopted LSP as an essential technology. These standards cover almost all cellular phones and IP phones worldwide.
|a2b=IEEE Tokyo Section, Japan
|IEEE units paying={{IEEE Organizational Unit Paying
|Unit=IEEE Tokyo Section, Japan
}}
|IEEE units arranging={{IEEE Organizational Unit Arranging
|Unit=IEEE Tokyo Section, Japan
}}
|IEEE sections monitoring={{IEEE Section Monitoring
|Section=IEEE Tokyo Section, Japan
}}
|Milestone proposers={{Milestone proposer
|Proposer name=Takehiro Moriya
|Proposer email=moriya.takehiro@lab.ntt.co.jp
}}
|a2a=NTT Musashino R&D center　
9-11, Midori-cho 3-Chome Musashino-Shi, Tokyo 180-8585 Japan
|a7=Initial invention, follow up investigations and developments have been carried out at this site.
|a8=No. New building has been built on the original site.
|mounting details=The plaque will be placed near the reception area in the ground floor entrance hall. All visitors have free access to this hall.
|a9=NTT’s receptionists are always near the plaque, and the plaque will be displayed in a transparent hard case.
|a10=NTT (Nippon Telegraph and Telephone) corporation
|permission letter=PermissionLetter(LSP).pdf
|support letter=Agreement.pdf
|a4=The line spectrum pair (LSP), invented in 1975, is one of the most efficient feature representation technologies for speech signals. Due to its number of practical merits for high-compression speech coding, it is commonly used worldwide in speech coding standards for cellular and IP phones, including 3GPP AMR (3G cellular in Europe and Japan), 3GPP2 EVRC (3G cellular in the USA and Japan), ITU-T G.723.1 and G.729 (IP phones), IETF SILK (software IP phones, Skype) , and PDC half (2G cellular in Japan), which cover almost all high-compression telephone communications systems that are widely used around the world now and will be in the future.
|a6=Auto-regressive linear prediction coding (LPC) technology is one of the most powerful and useful speech coding tools [1]. Pioneering investigations of the technology were independently and simultaneously started by Dr. B. S. Atal and Dr. M. R. Schroeder at AT&T Bell Labs in 1966, and by Dr. F. Itakura and Dr. S. Saito at NTT (Nippon Telegraph and Telephone) Labs. Representation and quantization of the prediction coefficients with less bit consumption and smaller LPC spectral distortion are the most critical issues in the LPC framework. At the same time, speech coding for cellular phones needs to be robust against transmission bit errors in the radio-wave environment. Thus, the representation method of predictive coefficients needs to achieve smaller LPC spectral distortion with fewer quantization bits while maintaining robustness against transmission channel errors.
|a5=It is possible to transmit prediction coefficients directly. Quantizing predictive coefficients, however, needs many bits for maintaining the LPC spectral shape. It is also difficult to avoid the risk of instability of the coding system.
Partial auto correlation (PARCOR), invented by Dr. F. Itakura and Dr. S. Saito in 1972, enables an easy stability check but still needs many bits of quantization to maintain the LPC spectral shape. It is possible to reduce bit consumption for quantizing PARCOR by applying adaptive bit allocation and variable length coding schemes. Both schemes are, however, extremely sensitive to transmission channel errors.
LSP, an alternative representation technology for prediction coefficients, was invented by Dr. F. Itakura in 1975 [2]. It enables a simple stability check and can maintain the LPC spectrum shape with around 30% less bit consumption than PARCOR, even without using adaptive bit allocation or the variable length coding schemes [3] – [7]. This is because the quantization distortion of LSP has smaller and more natural influences on LPC spectral shape than PARCOR. Thus, small LPC spectral distortion is achieved by efficient coding of LSP in combination with prediction, interpolation, and vector quantization.
|references=[1] B. S. Atal, “The History of Linear Prediction”, IEEE SIGNAL PROCESSING MAGAZINE, pp. 154-157, MARCH 2006.

[2] F. Itakura, “Line Spectrum Representation of Linear Predictive Coefficients of Speech Signals,” J. Acoust. Soc. Am., 57, 533(A), 1975.

[3] JP Patent 56051116 - ALL POLE TYPE DIGITAL FILTER invented by F. Itakura
http://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=8&ND=6&adjacent=true&locale=en_EP&FT=D&date=19810508&CC=JP&NR=56051116A&KC=A

[4] US Patent 4,393,272  Sound synthesizer invented by F. Itakura and N. Sugamura
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=4,393,272.PN.&OS=PN/4,393,272&RS=PN/4,393,272

[5] F. Itakura, “Statistical Methods for Speech Analysis and Synthesis –from ML Vocoder to LSP through PARCOR –,” IEICE　Fundamental Review Vol.3 No.3. 2010. (in Japanese)
Abstract: The invention process of the line spectrum air (LSP), one of the most important analysis technologies for speech signals, is described. Partial auto correlation (PARCOR) and LSP are alternative representation methods for a speech spectrum shape or a vocal tract shape. Both methods were invented at NTT Labs in 1972 and 1975, respectively. This paper covers the processes for these inventions, starting from the original invention of a speech analysis method based on maximum likelihood estimation in 1966.

[6] F. Itakura, T. Kobayashi and M. Honda, “A Hardware implementation of a new narrow and medium band speech coding,”, Proc. ICASSP 82, pp. 1964 – 1967, 1982.

[7] F. Soong and B. H. Juan, “Line spectrum pair (LSP) and speech data compression,” Proc. ICASSP 84, Vol. 9, pp. 37 – 40, 1984.
|supporting materials=[8] ITU-T G.723.1(Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s)
http://www.itu.int/rec/T-REC-G.723.1-200605-I,section 2.4-2.7

[9] ITU-T G.729(Coding of speech at 8 kbit/s using conjugate structure algebraic-code-excited linear prediction (CS-ACELP))
http://www.itu.int/rec/T-REC-G.729-200701-S, section 3.2

[10] 3GPP AMRhttp://www.etsi.org/deliver/etsi_ts/126000_126099/126090/10.01.00_60/ts_126090v100100p.pdf, section 5.2

[11] 3GPP2 EVRC
http://www.3gpp2.org/public_html/specs/C.S0014-0_v1.0_revised.pdf, section 4.2

[12] IETF SILKhttp://tools.ietf.org/html/draft-vos-silk-01, page 261

[13] Example of VoIP gateway supporting G. 729
http://www.cisco.com/en/US/docs/ios/solutions_docs/voip_solutions/CAC.html
|submitted=No
}}