1. A content providing and obtaining system composed of a content providing apparatus for providing compressed content data generated by compressively coding content data by a specified compression coding method, and a content obtaining apparatus applying a specified decoding method corresponding to the specified compression coding method, for obtaining said compressed content data provided from said content providing apparatus, wherein: said content providing apparatus comprises data storing means for storing said compressed content data compressively coded by one or more kinds of compression coding methods, information receiving means for receiving identification information for identifying said specified decoding method applied to the content obtaining apparatus, and specifying information representing specified content data, transmitted from said content obtaining apparatus, data detecting means for detecting whether or not specified compressed content data generated by compressively coding said specified content data by said specified compression coding method corresponding to said identification information has been stored in said data storing means, according to said identification information and said specifying information, reading means, according to the detection result by said data detecting means, if said specified compressed content data has been stored in said data storing means, for reading said specified compressed content data from said data storing means, compressively-coding means, according to the detection result by said data detecting means, if said specified compressed content data has not been stored in said data storing means, for compressively coding said specified content data being the original data of the above specified compressed content data by said specified compression coding method, and generating said specified compressed content data, and data transmitting means for transmitting said specified compressed content data read from said data storing means by said reading means, or said specified compressed content data generated by said compressively-coding means, to said content obtaining apparatus; and said content obtaining apparatus comprises information transmitting means for transmitting said identification information and said specifying information to said content providing apparatus, data receiving means for receiving said specified compressed content data transmitted from said content providing apparatus, and decoding means for decoding said specified compressed content data by said specified decoding method, and generating said specified content data.