Floating-point type digital signal reversible encoding method, decoding method, apparatuses therefor, and programs therefor

A decoding method for a digital signal in a floating-point format, comprising:

• (a) a step of decoding and expanding a first code sequence to produce a first signal sample in an integer format;
• (b) a step of producing a difference signal in the floating-point format from a second code sequence based on the number of digits capable of being non-zero that is determined by the absolute value of said first signal sample;
• (c) a step of converting said first signal sample in the integer format into a second signal sample in the floating-point format;
• and
• (d) a step of combining said second signal sample in the floating-point format and said difference signal in the floating-point format to produce a third signal sample in the floating-point format.

A lossless coder for a digital signal in a floating-point format, comprising:

• an integer formatting part that converts an input first signal sample in the floating-point format into a second signal sample in an integer format by truncation so that the absolute value thereof is reduced;
• a first compressing part that receives said second signal sample in the integer format and losslessly compresses the second signal sample to produce a first code sequence;
• a difference producing part that produces a difference signal in the floating-point format that corresponds to the difference between said second signal sample in the integer format and said first signal sample in the floating-point format;
• and
• second code sequence producing means that produces and outputs a second code sequence that corresponds to digits capable of being non-zero in said difference signal in the floating-point format, the digits being determined by the absolute value of said second signal sample in the integer format.

A decoder for a digital signal in a floating-point format, comprising:

• a first expansion part that receives a first code sequence and decodes and expands the first code sequence to produce a first signal sample in an integer format;
• difference signal decoding means that produces a difference signal in the floating-point format from a second code sequence based on the number of digits capable of being non-zero that is determined by the absolute value of said first signal sample;
• a floating point formatting part that receives said first signal sample in the integer format and converts the first signal sample into a second signal sample in the floating-point format;
• and
• a combining part receives said second signal sample in the floating-point format and said difference signal in the floating-point format and combines the second signal samples and the difference signal to produce a third signal sample in the floating-point format.