<P>PROBLEM TO BE SOLVED: To provide a BC-TCQ (Block-Constrained Trellis Coded Quantization) method having excellent SNR (Signal to Noise Ratio) performance by drastically reducing a memory size required in quantization of input signals and moduli and the amount of calculation and complexity in a code book searching process in a speech encoding system, and to provide a method and system for quantizing an LSF (line spectrum frequency) moduli by applying the BC-TCQ method. <P>SOLUTION: The method is characterised by including the stages of: removing a DC component from an LSF modulus vector; quantizing the first predicted error vector formed by subjecting the LSF modulus vector having the DC component removed to inter-frame and intra-frame prediction by using a BC-TCQ algorithm and obtaining the first LSF modulus vector quantized by inter-frame and intra-frame prediction compensation; quantizing the second predicted error vector formed by subjecting the LSF modulus vector having the DC component removed to the intra-frame prediction by using the BC-TCQ algorithm and obtaining the second LSF modulus vector quantized by the intra-frame prediction compensation; and selectively outputting a vector of the short Euclidean distance from the input LSF modulus vector among the quantized first and second LSF modulus vectors. <P>COPYRIGHT: (C)2004,JPO&NCIPI 
BLOCK-CONSTRAINED TRELLIS CODED QUANTIZATION METHOD AND QUANTIZATION METHOD AND SYSTEM FOR LINE SPECTRUM FREQUENCY MODULUS EMPLOYING THE TRELLIS CODED QUATIZATION METHOD IN SPEECH ENCODING SYSTEM