Acoustic signal encoding method and apparatus, acoustic signal decoding method and apparatus and recording medium

An acoustic signal decoding method for decoding acoustic signals in which tonal component signals are extracted from acoustic time-domain signals and encoded, and in which a code string obtained on encoding residual time-domain signals corresponding to said acoustic time-domain signals freed on extraction of said tonal component signals is input and decoded, said method comprising:

• a code string resolving step of resolving said code string;
• a tonal component decoding step of decoding the tonal component time-domain signals in accordance with the tonal component information obtained by said code string resolving step;
• a residual component decoding step of decoding residual component time-domain signals in accordance with the residual component information obtained by said code string resolving step;
• and
• a summation step of summing the tonal component time-domain signals obtained by said tonal component decoding step to the residual component time-domain signals obtained by said residual component decoding step to restore said acoustic time-domain signals.

An acoustic signal encoding method for encoding acoustic time-domain signals comprising:

• a frequency band splitting step of splitting said acoustic time-domain signals into a plurality of frequency bands;
• a tonal component encoding step of extracting tonal component signals from said acoustic time-domain signals of at least one frequency band and encoding the so extracted tonal component signals;
• and
• a residual component encoding step of encoding residual time-domain signals freed on extraction of said tonal component by said tonal component encoding step from said acoustic time-domain signals of at least one frequency range.

An acoustic signal decoding method in which acoustic time-domain signals are split into a plurality of frequency bands, tonal component signals are extracted from said acoustic time-domain signals in at least one frequency band and encoded, a code string obtained on encoding residual time-domain signals obtained in turn on extracting said tonal component signals from said acoustic time-domain signals of at least one frequency band is input, and in which the so input code string is decoded, said method comprising:

• a code string resolving step of resolving said code string;
• a tonal component decoding step of synthesizing, for said at least one frequency band, tonal component time-domain signals in accordance with the residual component information obtained by said code string resolving step;
• a residual component decoding step of generating, for said at least one frequency band, residual component time-domain signals in accordance with the residual component information obtained by said code string resolving step;
• a summation step of summing the tonal component time-domain signals obtained by said tonal component decoding step to the residual component time-domain signals obtained by said residual component decoding step;
• and
• a band synthesizing step of band-synthesizing decoded signals for each band to restore said acoustic time-domain signals.

An acoustic signal encoding method for encoding acoustic signals comprising:

• a first acoustic signal encoding step of encoding said acoustic time-domain signals by a first encoding method including a tonal component encoding step of extracting tonal component signals from said acoustic time-domain signals and encoding said tonal component signals, a residual component encoding step of encoding residual signals obtained on extracting said tonal component signals from said acoustic time-domain signals by said tonal component encoding step and a code string generating step of generating a code string from the information obtained by said tonal component encoding step and the information obtained from the residual component encoding step;
• a second acoustic signal encoding step of encoding said acoustic time-domain signals by a second encoding method;
• and
• an encoding efficiency decision step of comparing the encoding efficiency of said first acoustic signal encoding step to that of said second acoustic signal encoding step to select a code string with a better encoding efficiency.

An acoustic signal decoding method for decoding a code string which is selectively input in such a manner that a code string encoded by a first acoustic signal encoding step or a code string encoded by a second acoustic signal encoding step, whichever is higher in encoding efficiency, is selectively input and decoded, said first acoustic signal encoding step being such a step in which the acoustic signals are encoded by a first encoding method comprising generating a code string from the information obtained on extracting tonal component signals from acoustic time-domain signals and on encoding the tonal component signals and from the information obtained on encoding residual signals obtained in turn on extracting said tonal component signals from said acoustic time-domain signals, said second acoustic signal encoding step being such a step in which the acoustic time-domain signals are encoded by a second encoding method;

• wherein
• if the code string resulting from encoding in said first acoustic signal encoding step is input, said acoustic time-domain signals are restored by a first acoustic signal decoding step including a code string resolving step of resolving said code string into the tonal component information and the residual component information, a tonal component decoding step of generating the tonal component time-domain signals in accordance with the tonal component information obtained in said code string resolving step, a residual component decoding step of generating residual component time-domain signals in accordance with said residual component information obtained in said code string resolving step and a summation step of summing said tonal component time-domain signals to said residual component time-domain signals;
• if the code string obtained on encoding in said second acoustic signal encoding step is input, said acoustic time-domain signals are restored by a second acoustic signal decoding sub-step corresponding to said second acoustic signal encoding step.

An acoustic signal decoding apparatus in which a code string resulting from extracting tonal component signals from acoustic time-domain signals, encoding said tonal component signals and from encoding residual time-domain signals corresponding to said acoustic time-domain signals freed on extraction of said tonal component signals, is input and decoded, said apparatus including:

• code string resolving means for resolving said code string;
• tonal component decoding means for decoding the tonal component time-domain signals in accordance with the tonal component information obtained by said code string resolving means;
• residual component decoding means for decoding the residual time-domain signals in accordance with the residual component information obtained by said code string resolving means;
• and
• summation means for summing the tonal component time-domain signals obtained from said tonal component decoding means and the residual component time-domain signals obtained from said residual component decoding means to restore said acoustic time-domain signals.

A computer-controllable recording medium having recorded thereon an acoustic signal encoding program of encoding acoustic time-domain signals, wherein said acoustic signal encoding program includes a code string resolving step of resolving said code string;

• a tonal component decoding step of decoding the tonal component time-domain signals in accordance with the tonal component information obtained by said code string resolving step;
• a residual component decoding step of decoding the residual time-domain signals in accordance with the residual component information obtained by said code string resolving step;
• and
• a summation step of summing the tonal component time-domain signals obtained from said tonal component decoding step and the residual component time-domain signals obtained from said residual component decoding step to restore said acoustic time-domain signals.