Editing Qualcomm code-excited linear prediction

{{short description|Speech codec by Qualcomm}}
{{inline|date=July 2009}}
{{Infobox file format
| name = Qualcomm PureVoice
| icon = 
| logo =
| extension = .qcp
| mime = audio/qcelp
| type code =
| uniform type = 
| magic = 
| owner = [[Qualcomm]]
| type = [[Lossy compression|Lossy]] [[Audio file format|audio]]
| container for =
| contained by = 
| extended from = 
| extended to = 
| standard = 
| released = {{start date and age|1994|df=y}}
| latest_release_version = TIA IS-733
| latest_release_date = {{start date and age|1999|12|df=y}}
| open = Yes
| free = No
}}
'''Qualcomm code-excited linear prediction''' ('''QCELP'''), also known as '''Qualcomm PureVoice''', is a [[speech codec]] developed in 1994 by [[Qualcomm]] to increase the speech quality of the [[IS-96A]] codec earlier used in [[code-division multiple access|CDMA]] networks. It was later replaced with [[Enhanced Variable Rate Codec|EVRC]] to achieve better speech quality with fewer bits. The two versions, ''QCELP8'' and ''QCELP13'', operate at 8 and 13 [[kilobits per second]] (Kbit/s) respectively.

In [[Code-division multiple access|CDMA]] systems, a QCELP [[vocoder]] converts a sound signal into a signal transmissible within a circuit. In wired systems, voice signals are generally sampled at 8&nbsp;kHz (that is, 8,000 sample values per second) and then encoded by 8-bit [[Quantization (signal processing)|quantization]] for each sample value. Such a system transmits at 64&nbsp;kbit/s, an expensive rate in a wireless system. A QCELP vocoder with variable rates can reduce the rate enough to fit a wireless system by [[Line coding|coding]] the information more efficiently. In particular, it can change its own coding rates based on the speaker's volume or pitch; a louder or higher-pitched voice requires a higher rate.

==References==
* https://web.archive.org/web/20130129041829/http://www.rfdh.com/ez/system/db/lib_jnl/upload/2489/[CSD9904]_QCELP_Vocoders_in_CDMA_Systems_Design.pdf
* [https://www.rarewares.org/rrw/purevoice.php Archived PureVoice encoder and player downloads]

{{Compression formats}}
{{Compression Software Implementations}}

{{DEFAULTSORT:Qcelp}}
[[Category:Speech codecs]]
[[Category:Qualcomm]]