Code-excited linear prediction: Difference between revisions

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{{shortShort description|CodingSpeech coding algorithm}}

{{No footnotes|date=May 2022}}

'''Code-excited linear prediction''' ('''CELP''') is a [[linear predictive coding|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{{Citation needed|reason=No sources to back this claim up.|date=November 2016}}. 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.

==IntroductionBackground==

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");

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==See also==

* [[MPEG-4 Part 3]] (CELP as an MPEG-4 Audio Object Type)

* [[G.728]] – Coding of speech at 16  kbit/s using low-delay code excited linear prediction

* [[G.718]] – uses CELP for the lower two layers for the band (50–6400 Hz) in a two-stage coding structure

* [[G.729.1]] – uses CELP coding for the lower band (50–4000 Hz) in a three-stage coding structure

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* This article is based on a [http://people.xiph.org/~jm/papers/speex_lca2006.pdf paper] presented at [http://linux.conf.au/ Linux.Conf.Au]

* Some parts based on the [[Speex]] codec [https://www.speex.org/docs/ manual]

* [http://www.speech.cs.cmu.edu/comp.speech/Section3/Software/celp-3.2a.html reference implementations] of CELP 1016A (CELP 3.2a) and LPC 10e. {{Webarchive|url=https://web.archive.org/web/20161212000335/http://www.speech.cs.cmu.edu/comp.speech/Section3/Software/celp-3.2a.html |date=2016-12-12 }}

* [https://web.archive.org/web/20090602220112/http://www.otolith.com/otolith/olt/lpc.html Linear Predictive Coding (LPC)]

=== Selected readings ===

* [https://www.speex.org/docs/manual/speex-manual/node9.html Introduction to CELP Coding]

* [https://cnx.org/content/m10482/latest/ Speech Processing: Theory of LPC Analysis and Synthesis] {{Webarchive|url=https://web.archive.org/web/20140615041652/http://cnx.org/content/m10482/latest/ |date=2014-06-15 }}

{{Compression Methods}}

{{Compression formats}}

[[Category:Speech codecs]]

[[Category:Data compression]]