1. A content retrieval method, comprising: extracting a plurality of fingerprints including a plurality of video fingerprints and a plurality of audio fingerprints from contents stored in a content database, the contents having video frames corresponding to the plurality of video fingerprints and associated audio sequences corresponding to the plurality of audio fingerprints; determining representative video fingerprints of the video frames and representative audio fingerprints of the audio sequences; determining a data rate indicating a storage limitation and a coverage indicating a number of searching results to be returned; storing selected representative video fingerprints and representative audio fingerprints based on the storage limitation indicated by the data rate in a fingerprint database; receiving a query containing at least one of video data and audio data submitted by a user; extracting at least one query fingerprint representing the query; determining a number of fingerprints most matching the at least one query fingerprint based on the coverage to generate search results indicating matching contents represented by the number of most matching fingerprints; and returning the search results to the user.