History of LPC Digital Speech and its impact on the Internet Protocol

Created 6 January 2011
Last modified: 12 February 2021

The following material is intended to supplement the article ``Digital speech and the Internet protocol: the 1974 origins of VoIP,'' which appeared in the IEEE Signal Processing Magazine, Vol. 22, July 2005, pp. 87-90, and the 2010 book Linear Predictive Coding and the Internet Protocol: A survey of LPC and a History of of Realtime Digital Speech on Packet Networks, A short book expanding on the basic story.

The book also appeared as a two part article in Foundations and Trends in Signal Processing published by Now Publishers:

"A survey of linear predictive coding: Part I of Linear Predictive Coding and the Internet Protocol," Foundations and Trends in Signal Processing, Vol. 3, No. 3, pp. 153-202.
"A history of realtime digital speech on packet networks: Part II of Linear Predictive Coding and the Internet Protocol," Foundations and Trends in Signal Processing, Vol. 3, No. 4, pp. 203-303153-203.

Supporting materials

• A complete scanned version of the June 3, 1982, Packet Speech Program Review Meeting. This roughly 16M file is a low resolution pdf of the proceedings of the meeting at MIT Lincoln Lab which closed the project. Many thanks to Earl Craighill for loaning me his copy. I have higher resolution scans available on request. The report includes slides presented by many of the major players in the development of realtime voice over the ARPAnet, PRnet, SATnet, and WBSATnet as well as related algorithmic and hardware developments.
• A version of the talk presented to the Computer Club on 29 June 2006, another at Research Triangle Park, North Carolina, 11 June 2007.
• The original talk California Coding: Early LPC Speech in Santa Barbara, Marina del Rey, and Silicon Valley, 1967-1982 was presented in January 2004 at the Special Workshop in Maui:Lectures by Masters in Speech Processing. The talk describes several threads of the history of LPC speech with an emphasis on Pacific rim contributions. One of the stories is the development of the first packet speech protocols and experiments on the ARPANET, especially the first documented real-time packet speech communication between Lincoln Labs and Culler-Harrison, Inc. in December 1974. The talk includes extensive references to both published and company documentation.
• The updated version for the August 2004 presentation at the University of California, Santa Barbara. The update includes further details regarding the ARPANET and Internet side of the story.
• The MPG video of the 1976 packet speech conference on the ARPANET shown in the talk.
• The official RFC for Specifications for the Network Voice Protocol, NSC Note 68, January 1976.
• For Interenet history with reference to the separation of IP from TCP, see B.M. Leiner, V.S. Cerf, D.D. Clark, R.E. Kahn, L. Kleinrock, D.C. Lynch, J. Postel, L. Kleinrock, D.C. Lynch, J. Postel, L. C. Roberts, S.S. Wolff, ``The past and future history of the Internet,'' Communications of the ACM, Vol. 40, No. 2, 102--108, February 1997. See also https://www.internetsociety.org/internet/history-internet/brief-history-internet/ . Barry was my first PhD student and he went on from information theory to become a pioneer in information technology as well as an Internet historian. See Bob Kahn's Memorial Tribute to Barry Leiner

  For other historical information on the Internet, see https://comparite.ch/historyofinternet for a broader recent view of history not emphasizing the TCP separation from IP, but discussing more aspects of the Internet, including the early consumer driving applications of email and the World Wide Web, and http://www.pcbargainhunter.com/articles/history-of-the-internet.html, which provides another perspective.

• The Voice over IP Forum. See in particular the "Materials Submitted to the VoIP Forum" link with opinions from Bob Kahn (Corporation for National Research Initiatives) and several polititians, companies, and scientists.

Robert M. Gray