Code‐Excited Linear Prediction
Wai C. Chu · 2003
The idea of code-excited linear prediction (CELP) was born as another attempt to improve on the existent LPC coder. CELP is among one of the most influential ideas in speech coding. Its principles lay the foundation for many standardized coders. In this chapter, generic techniques of CELP are given; the architecture, functionality, and constraint are described without referring to any particular standard. Thorough understanding of the material in this chapter is crucial for later chapters, where details of several CELP-based standards are described. The chapter begins with the speech production model, followed by an explanation of the principle of analysis-by-synthesis; operations of the encoder and decoder are described. Two important components—excitation codebook search and the postfilter—are analyzed and presented.