In data compression, vector quantization is a quantization technique often used in lossy data compression in which the basic idea is to code values from a multidimensional vector space into values from a discrete subspace of lower dimension. The lower-space vector requires less storage space and the data is thus compressed. The transformation into the subspace is usually achieved through projection, or by using a codebook. In some cases, a codebook implementation can be also used to entropy code the discrete value in the same step by generating a prefix coded variable-length encoded value as its output.