Abstract: Provided are techniques which offer an advantage of reduced time and reduced storage capacity required to calculate the feature value of AAC-format song data. A feature extraction unit includes: an MDCT coefficient extraction unit which extracts MDCT coefficients from AAC-format song data; a classification unit which locates the MDCT coefficients thus extracted by the MDCT coefficient extraction unit on Mel frequency regions so as to uniformly classify the MDCT coefficients into classes, the number of which is the same as that of a predetermined number of Mel filter banks; an integrating unit which extracts the MDCT coefficients classified by the classification unit by applying a predetermined window function, and integrates the MDCT coefficients thus extracted, in increments of the Mel filter banks; and a feature calculation unit which calculates the feature value by performing logarithmic cosine conversion of the integrated results obtained by the integrating unit.

Abstract: An apparatus for retrieving music that matches with a user preference across a plurality of music is provided. The apparatus comprises a feature vector generating device for generating feature vectors of each of the music, a clustering device for clustering the music into a plurality of clusters according to the feature vectors, a music extraction device for extracting a predetermined number of music from each of the clusters, a music selection accepting device for accepting a selection of music by the user from the music, and a music retrieval device for calculating similarities between a feature vector of the selected music and feature vectors of each of the music, and retrieving music that have higher similarities to the selected music among the music.

Abstract: Provided are techniques which offer an advantage of reduced time and reduced storage capacity required to calculate the feature value of AAC-format song data. A feature extraction unit includes: an MDCT coefficient extraction unit which extracts MDCT coefficients from AAC-format song data; a classification unit which locates the MDCT coefficients thus extracted by the MDCT coefficient extraction unit on Mel frequency regions so as to uniformly classify the MDCT coefficients into classes, the number of which is the same as that of a predetermined number of Mel filter banks; an integrating unit which extracts the MDCT coefficients classified by the classification unit by applying a predetermined window function, and integrates the MDCT coefficients thus extracted, in increments of the Mel filter banks; and a feature calculation unit which calculates the feature value by performing logarithmic cosine conversion of the integrated results obtained by the integrating unit.

Abstract: An apparatus for retrieving music that matches with a user preference across a plurality of music is provided. The apparatus comprises a feature vector generating device for generating feature vectors of each of the music, a clustering device for clustering the music into a plurality of clusters according to the feature vectors, a music extraction device for extracting a predetermined number of music from each of the clusters, a music selection accepting device for accepting a selection of music by the user from the music, and a music retrieval device for calculating similarities between a feature vector of the selected music and feature vectors of each of the music, and retrieving music that have higher similarities to the selected music among the music.

Abstract: A document retrieval apparatus is connected to a network, and includes a cluster database storing a cluster of node information elements linked for clustering the documents to a hierarchical tree structure based on degree of similarity in all of the documents. The apparatus can post to an end address in the node information element encountered on the way to follow links of the cluster by whenever one of the documents is updated. Also, the apparatus selects a specific number of documents, clusters those, assigns the remaining non-selected documents respectively to a leaf node to be similar to the documents in the cluster, and repeats recursively the above operations toward a direction of the leaf node of cluster.