Qualcomm code-excited linear prediction
Nowadays, Qualcomm code-excited linear prediction has become a topic of great relevance in today's society. With the advancement of technology and globalization, Qualcomm code-excited linear prediction has acquired significant importance in different areas, from politics to economics, science and culture. Throughout history, Qualcomm code-excited linear prediction has been the subject of study and debate, generating conflicting opinions and deep reflections on its impact on people's lives. In this article, we will explore different perspectives and approaches on Qualcomm code-excited linear prediction, with the aim of offering a comprehensive and enriching vision on a topic that arouses the interest of millions of individuals around the world.
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| Filename extension |
.qcp |
|---|---|
| Internet media type |
audio/qcelp |
| Developed by | Qualcomm |
| Initial release | 1994 |
| Latest release | TIA IS-733 December 1999 |
| Type of format | Lossy audio |
| Open format? | Yes |
| Free format? | 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 CDMA networks. It was later replaced with 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 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 kHz (that is, 8,000 sample values per second) and then encoded by 8-bit quantization for each sample value. Such a system transmits at 64 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 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/_QCELP_Vocoders_in_CDMA_Systems_Design.pdf
- Archived PureVoice encoder and player downloads