Editing Half Rate

{{Short description|Speech coding standard}}
'''Half Rate''' ('''HR''' or '''GSM-HR''' or '''GSM 06.20''') is a [[speech coding]] system for [[GSM]], developed in the early 1990s.

Since the [[codec]], operating at 5.6&nbsp;kbit/s, requires half the [[Bandwidth (computing)|bandwidth]] of the [[Full Rate]] codec, network capacity for voice traffic is doubled, at the expense of audio quality. The sampling rate is 8&nbsp;kHz with resolution 13 bit, frame length 160 samples (20 ms) and subframe length 40 samples (5 ms).

GSM Half Rate is specified in [[European Telecommunications Standards Institute|ETSI]] EN 300 969 (GSM 06.20), and uses a form of the [[Vector sum excited linear prediction|VSELP]] algorithm.<ref>ETSI, [http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=10142 EN 300 969 - Half rate speech transcoding (GSM 06.20 version 8.0.1 Release 1999)], Retrieved on 2009-07-11</ref> Previous specification was in [[ETSI]] ETS 300 581–2, which first edition was published in December 1995.<ref>[http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=6242 ETSI ETS 300 581-2 - Half rate speech transcoding (GSM 06.20 version 4.3.1)], Retrieved on 2009-07-11</ref>

For some Nokia phones one can configure the use of this codec:

* To activate HR codec use enter the following code: *4720#
* To deactivate HR codec use enter the following code: #4720#

==See also==
* [[Full Rate]]
* [[Enhanced Full Rate]] (EFR)
* [[Adaptive Multi-Rate]] (AMR)
* [[Adaptive Multi-Rate Wideband]] (AMR-WB)
* [[Extended Adaptive Multi-Rate - Wideband]] (AMR-WB+)

==References==
{{reflist}}

==External links==
* [http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=10142 ETSI EN 300 969 - Half rate speech transcoding (GSM 06.20 version 8.0.1 Release 1999)] - technical specification
* [http://webapp.etsi.org/workprogram/Report_WorkItem.asp?WKI_ID=6242 ETSI ETS 300 581-2 - Half rate speech transcoding (GSM 06.20 version 4.3.1)] - obsoleted
* [http://www.3gpp.org/ftp/Specs/html-info/0620.htm 3GPP TS06.20] - technical specification
* {{IETF RFC|5993|link=no}} - RTP Payload format for GSM-HR


{{Compression formats}}

[[Category:Audio codecs]]
[[Category:Speech codecs]]

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