LPC

THE CVSD CODEC IS DESIGNED FOR USE IN MILITARY COMMUNICATION SYSTEMS

Linear Predictive Coding

Audio Technology

Features List

  • Functions are C-callable.
  • Excellent choice for very low bit rate communication systems
  • Useful for developing backward compatible equipment based upon DSP technology

Coding Rate: 2.4 kbps

Sampling Rate: 8 kHz

Availability

Platforms
Texas Instruments – TI TMS320C6000 C67x

ADT LPC is available on the above Platforms: Other configurations are available upon request.

Specifications

LPC C67x

CPU UTILIZATION & MEMORY REQUIREMENTS
Memory usage is given in units of byte.
FunctionPeak Loading MIPSProgram MemoryData Memory
Encode1055 k31 k
Decode14.6
Encode/Decode24.6

Description

The Adaptive Digital Technologies LPC-C67Xvoice coder is a real-time implementation of one of the LPC-10 vocoder. LPC analyzes the speech signal by estimating the formants*, removing their effects from the speech signal, and estimating the intensity and frequency of the remaining buzz. The process of removing the formants is called inverse filtering, and the remaining signal after the subtraction of the filtered modeled signal is called the residue.

The LPC vocoder algorithm is a form of voice compression commonly used for speech analysis and resynthesis. It is also used for secure wireless, where voice must be digitized, encrypted and sent over a narrow voice channel.

 

* A formant is a concentration of acoustic energy around a particular frequency in the speech wave. There are several formants, each at a different frequency, roughly one in each 1000Hz band. Or, to put it differently, formants occur at roughly 1000Hz intervals. Each formant corresponds to a resonance in the vocal tract.

Function API's​

API function call summary

LPCinit(. . .) 
LPCencode(. . .) 
LPCdecode(. . .)

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