Sampling frequency converting apparatus

A sampling frequency converting apparatus for converting an input first digital signal having an input sampling frequency Fsi (Hz) into a second digital signal having a variable output sampling frequency Fso (Hz), comprising:

• input signal system reference clock signal generating means for generating a clock signal having a frequency of N.times.Fsi (Hz) which is N times (N is a positive integer) as high as said input sampling frequency Fsi (Hz);
• output signal system reference clock signal generating means for generating a clock signal having said variable sampling frequency Fso (Hz);
• input/output sampling frequency ratio measuring means for determining a ratio of said input sampling frequency Fsi (Hz) to said variable sampling frequency Fso (Hz);
• linear interpolation means for linearly interpolating at a regular time interval said ratio determined by said input/output sampling frequency ratio measuring means;
• over-sampling means for oversampling said first digital signal having said input sampling frequency Fsi (Hz);
• storage means for temporarily storing said over-sampled first digital signal supplied from said over-sampling means;
• address generating means for generating a read address for said over-sampled first digital signal stored in said storage means based on a linear interpolation value of said ratio output from said linear interpolation means;
• and
• converting means for reading out said over-sampled first digital signal from said storage means based on said read address generated by said address generating means and converting said over-sampled first digital signal into said second digital signal having said variable output sampling frequency Fso (Hz).