A processor-implemented method includes: determining distances between an input vector and center vectors comprised in a plurality of output nodes comprised in a trained codebook; and outputting a first feature vector of the input vector based on the distances between the center vectors and the input vector, wherein the trained codebook is trained by: determining a distance between a training input vector and the center vector for each of the output nodes; determining, among the plurality of output nodes, a best matched unit (BMU) in which a distance between the training input vector and the center vector of the BMU is minimized; and training the codebook by updating the center vector of the BMU, based on the distance between the training input vector and the center vector of the BMU.