Methods, apparatuses and recorded medium for reversible encoding and decoding

An encoding method for encoding a digital signal for each frame comprising a plurality of samples expressed in sign-magnitude format, comprising:

• a step for reversible encoding a bitstream within a frame over samples in said error signal;
• a step for reconstructing a local reconstructed signal for said irreversible compression code;
• a step for obtaining an error signal between said local reconstructed signal and said digital signals;
• and
• a step for generating a reversible compression code by reversible encoding a bitstream within a frame over samples in said error signals;
• wherein when reversible encoding said bitstream, said bitstream is encoded to a reversible compression code corresponding to the bitstream for each bit position from the most significant bit position to a jth position, said j being a predetermined integer.

A decoding method comprising:

• a step for reconstructing an error signal for each frame comprising a plurality of samples in a sign-magnitude format by reversible decoding of a reversible compression code;
• and
• a step for reconstructing a local reconstructed signal by irreversible decoding of an irreversible compression code;
• a step for generating a digital signal by adding said error signal and said local reconstructed signal,
• wherein when restoring the error signal, a bitstream of the error signal is restored for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer.

An encoding method for encoding a digital signal for each frame comprising a plurality of samples in a sign-magnitude format comprising:

• a step for generating an irreversible compression code for said digital signal;
• a step for reconstructing a local reconstructed signal for said irreversible compression code;
• a step for selecting either an error signal between said local reconstructed signal and said digital signal, or said digital signal;
• a step for generating selective information indicating whether said error signal or said digital signal is selected;
• and
• a step for generating a reversible compression code by reversible encoding of a bitstream within a frame over samples in said selected signal,
• wherein when reversible encoding said bitstream, said bitstream is encoded to said reversible compression code corresponding to the bitstream for each bit position from the most significant bit position to a jth position, said j being a predetermined integer.

A decoding method comprising:

• reconstructing a reconstructed signal for each frame comprising a plurality of samples in a sign-magnitude format by decoding a reversible compression code into a bitstream comprising bits within a frame over samples for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer;
• if selective information indicates that a digital signal is selected, said reconstructed signal is output as digital signal;
• and
• if selective information indicates that an error signal is reversibly quantized, reconstructing a local reconstructed signal for an irreversible compression code, and generating a digital signal by adding said reconstructed signal and said local reconstructed signal.

An encoding method for encoding a digital signal for each frame comprising a plurality of samples in a sign-magnitude format, comprising:

• a step for generating a reversible compression code by reversible encoding of the most significant t-bit of absolute amplitude values of said digital signal;
• a step for generating an irreversible compression code by irreversible encoding of a signal which is obtained by arithmetically t-bit upward shifting of the absolute amplitude values of said digital signal;
• a step of reconstructing a local reconstructed signal for said irreversible compression code;
• a step for obtaining an error signal between said digital signal and a signal which is obtained by arithmetically t-bit downward shifting of said local reconstructed signal;
• and
• a step for encoding of a bitstream comprising bits within a frame over samples to a code corresponding to the bitstream for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer.

A decoding method comprising:

• restoring an error signal for each frame comprising a plurality of samples in sign-magnitude format by decoding a reversible compression code into a bitstream comprising bits within a frame over samples corresponding to said reversible compression code for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer;
• restoring a local reconstruction signal by decoding an irreversible compression code;
• a step for generating bits for bit positions other than the most significant t-bit positions of absolute amplitude values by adding said error signal and a signal which is obtained by arithmetically t-bit downward shifting of said local reconstructed signal;
• a step for reconstructing bits for said most significant t-bit positions by reversible decoding of a reversible compression code;
• and
• a step for generating a digital signal by adding bits for said most significant t-bit positions and said bits for bit positions other than said most significant t-bit positions.

An encoding apparatus for encoding a digital signal for each frame comprising a plurality of samples expressed in sign-magnitude format, comprising:

• means for irreversible encoding of said digital signal to an irreversible compression code;
• means for reconstructing a local reconstructed signal for said irreversible compression code;
• means for obtaining an error signal between said local reconstructed signal and said digital signal;
• and
• means for reversible encoding of a bitstream comprising bits within a frame over samples in said error signal;
• wherein when reversible encoding said bitstream, said bitstream is encoded to a reversible compression code corresponding to the bitstream for each bit position from the most significant bit position to a jth position, said j being a predetermined integer.

A decoding apparatus comprising:

• means for reconstructing an error signal for each frame comprising a plurality of samples in a sign-magnitude format by reversible decoding of a reversible compression code;
• and
• means for generating a digital signal by adding said error signal and said local reconstructed signal,
• wherein when restoring the error signal, the means for reconstructing an error signal restores a bitstream of the error signal for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer.

An encoding apparatus for encoding a digital signal for each frame comprising a plurality of samples in sign-magnitude format, comprising:

• means for generating an irreversible compression code for said digital signal,
• means for reconstructing a local reconstructed signal for an irreversible compression code,
• means for selecting of either an error signal between said local reconstructed signal and said digital signal, or said digital signal,
• means for generating selective information indicating whether said error signal or said digital signal is selected, and
• means for generating a reversible compression code by reversible encoding a bitstream within a frame over samples in said error signal;
• wherein when reversible encoding said bitstream, said bitstream is encoded to a reversible compression code corresponding to the bitstream for each bit position from the most significant bit position to a jth position, said j being a predetermined integer.

An encoding apparatus for encoding a digital signal for each frame comprising a plurality of samples in sign-magnitude format, comprising:

• means for generating a reversible compression code by reversible encoding of the most significant t-bit of absolute amplitude values of said digital signal;
• means for generating an irreversible compression code by irreversible encoding of a signal which is obtained by arithmetically t-bit upward shifting of the absolute amplitude values of said digital signal;
• means for reconstructing a local reconstructed signal for said irreversible compression code;
• means for obtaining an error signal between said digital signal and a signal which is obtained by arithmetically t-bit downward shifting of said local reconstructed signal;
• and
• means for encoding a bitstream of said error signal comprising bits within a frame over the samples to a code corresponding to the bitstream for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer.

A decoding apparatus comprising:

• means for reconstructing an error signal for each frame comprising a plurality of samples in a sign-magnitude format by decoding a reversible compression code into a bitstream comprising bits within a frame over samples corresponding to said reversible compression code for each bit position from the most significant bit position to a jth bit position, said j being a predetermined integer;
• means for reconstructing a local reconstructed signal by decoding an irreversible compression code;
• means for generating bits for bit positions other than the most significant t-bit positions of absolute amplitude values by adding said error signal and a signal which is obtained by arithmetically t-bit downward shifting of said local reconstructed signal;
• means for reconstructing bits for said most significant t-bit positions by reversible decoding of a reversible compression code;
• and
• means for generating a digital signal by adding bits for said most significant t-bit positions and said bits for bit positions other than said most significant t-bit positions.