View source for Enhanced Variable Rate Codec

{{Short description|Speech codec used by CDMA networks}}
'''Enhanced Variable Rate CODEC''' ('''EVRC''') is a [[speech codec]] used in [[CDMA]] networks. It was developed in 1995 to replace the [[QCELP]] vocoder which used more bandwidth on the carrier's network, thus EVRC's primary goal was to offer the mobile carriers more capacity on their networks while not increasing the amount of bandwidth or wireless spectrum needed.<ref>[http://telephonyonline.com/wireless/mag/wireless_evrc_best_worlds/ EVRC: Best of Both Worlds<!-- Bot generated title -->]</ref> EVRC uses [[RCELP]] technology.

EVRC compresses each 20 milliseconds of 8000&nbsp;Hz, 16-bit sampled speech input into output frames of one of three different sizes: full rate – 171 bits (8.55&nbsp;kbit/s), half rate – 80 bits (4.0&nbsp;kbit/s), eighth rate – 16 bits (0.8&nbsp;kbit/s). A quarter rate was not included in the original EVRC specification and eventually became part of [[EVRC-B]]. 

EVRC was replaced by [[Selectable Mode Vocoder|SMV]]. Recently, however, [[Selectable Mode Vocoder|SMV]] itself has been replaced by the new [[CDMA2000]] 4GV codecs. [[4GV]] is the next generation [[3GPP2]] standards-based [[EVRC-B]] codec. 4GV is designed to allow service providers to dynamically prioritize voice capacity on their network as required.

EVRC can be also used in 3GPP2 container file format - [[3GP|3G2]].

==References==
{{reflist}}

== External links ==
* [https://web.archive.org/web/20041102191849/http://www.3gpp2.org/Public_html/Specs/C.S0014-A_v1.0_040426.pdf 3GPP2 specification]
* [https://web.archive.org/web/20041204051511/http://www.arcx.com/sites/EVRC.htm EVRC – The Savior of CDMA?]
* {{IETF RFC|4788|link=no}} - Enhancements to RTP Payload Formats for EVRC Family Codecs

{{Compression formats}}

[[Category:Speech codecs]]
[[Category:3rd Generation Partnership Project 2 standards]]


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