it provided significantly better quality than existing low bit-rate algorithms, such as RELP and LPC
vocoders
Introduction
The CELP algorithm is based on four main ideas:
• Using the source-filter model of speech production through linear prediction...
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it provided significantly better quality than existing low bit-rate algorithms, such as RELP and LPC
vocoders
Introduction
The CELP algorithm is based on four main ideas:
• Using the source-filter model of speech production through linear prediction (LP)(see the
textbook "speech coding algorithm");
• Using an adaptive and a fixed codebook as the input (excitation) of the LP model;
• Performing a search in closed-loop in a “perceptually weighted domain”.
• Applying vector quantization (VQ)
• Before exploring the complex encoding process of CELP we introduce the decoder here.
Figure 1 describes a generic CELP decoder.
The excitation is produced by summing the
contributions from an adaptive (aka pitch) codebook and a fixed (aka innovation or
stochastic) codebook:
•
• where ea[n] is the adaptive (pitch) codebook contribution and ef[n] is the fixed
(innovation) codebook contribution.
The fixed codebook is a vector quantization
dictionary that is (implicitly or explic
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