The present invention relates to a signal processing apparatus and method, a recording medium, and a program enabling accurate calculation of a remaining amount of a tape. In a cassette shell 1, a memory 13 for storing information indicative of a total length of a magnetic tape 11 is incorporated. A remaining-tape-amount calculation apparatus 22 calculates a length of the tape as an amount of being wound around a reel 12-1 and a reel 12-2 on an assumption of a thickness of the tape being constant, and, for example, corrects a calculated tape length of the tape being retained wound around the reel 12-1 using a ratio of the total length of the magnetic tape 11, read out from the memory, to a sum of the calculated tape length of the tape being retained wound around the reel 12-1 and the tape length of the tape being put on wound around the reel 12-2 to calculate a remaining amount of the magnetic tape 11, which is recordable or reproducible. Incidentally, it is possible to apply the present invention to a VTR.