Waveform compressing apparatus, waveform decompressing apparatus, and method of producing compressed data

A waveform compressing apparatus for converting an original waveform data into a compressed data having a plurality of frames of a predetermined format, each frame containing a residue code and sub information specifying a mode applied to generation of the residue code, the waveform compressing apparatus comprising:

• a mode selecting device that selects one mode that is applied to generation of the residue code from a plurality of candidate modes, wherein said plurality of candidate modes are vector quantization modes using a vector quantization method in generating the residue code;
• a waveform data compressing device that generates the residue code in accordance with the selected mode by compressing a portion of the original waveform data, the portion amount being determined in correspondence with the selected mode;
• and
• a frame storing device that stores the generated residue code and sub information specifying the selected mode to the frame.

A method of producing a compressed data with a given compression rate based on an original waveform data, the compressed data having a plurality of frames of a predetermined format, each frame containing a residue code and sub information specifying a mode applied to generation of the residue code, the method comprising:

• a trial mode selecting process of selecting a trial mode having the highest compression rate from a plurality of candidate modes that have not been previously selected as a trial mode for generating the residue code;
• a waveform data compressing process of compressing a portion of the original waveform data according to the selected trial mode so as to generate the residue code corresponding to the selected trial mode, the portion amount being specified by the selected trial mode;
• a waveform data restoring process of restoring a generated waveform data from the compressed data using the generated residue code;
• a determining process of determining an evaluation value that indicates a quantization error contained in the restored waveform data relative to the original waveform data, and determining whether the evaluation value is equal to or smaller than a predetermined allowable value;
• a mode change instructing process of outputting a mode change instruction for instructing the trial mode selecting process to select another trial mode when the determining process determines that the evaluation value is not equal to or smaller than the predetermined allowable value;
• and
• a frame storing process of storing the generated residue code and the sub information specifying the selected trail mode in the frame when the determining process determines that the evaluation value is equal to or smaller than the predetermined allowable value.

A method of producing a compressed data having a plurality of frames of a predetermined format based on an original waveform data, each frame containing a residue code and sub information specifying a mode applied to generation of the residue code, the method comprising:

• a mode selecting process of selecting one mode that is applied to generation of the residue code from a plurality of candidate modes, wherein said plurality of candidate modes are vector quantization modes using a vector quantization method in generating the residue code;
• a waveform data compressing process of generating the residue code in accordance with the selected mode by compressing a portion of the original waveform data, the portion amount being determined in correspondence with the selected mode;
• and
• a frame storing process of storing the residue code and sub information specifying the selected mode to the frame.