Compressed data structure and apparatus and method related thereto

A computer-readable program containing a group of instructions embodied on a computer-readable medium for causing the computer to perform a tone signal generation method for generating a tone signal by use of a memory storing a plurality of frames each including compression codes obtained by compressing waveform data over a portion thereof and decompression parameters for decompressing the compression codes of a next portion, said method comprising:

• a step of generating readout addresses in such a manner that the readout addresses vary at a rate corresponding to a pitch of a tone signal to be generated;
• a readout step of reading out data of the frames from said memory on the basis of the readout addresses generated by said step of generating;
• a step of taking out, from the data read out by said readout step, the decompression parameters included in each of the frames, the decompression parameters included in a given one of the frames becoming available upon completion of readout of all of the data included in the given frame;
• a decompression step of decompressing the compression codes of a particular portion included in any one of the frames read out by said readout step, on the basis of the decompression parameters of said particular portion having been included in a previously-read-out frame, to thereby reproduce a tone signal;
• and
• a step of, on condition that the readout address has reached a loop end point, setting the readout address at a loop start point;
• and
• a step of outputting a tone corresponding to the reproduced tone signal,
• wherein at least one of the loop start point and loop end point is set at an enroute point of the portion to which the loop start point or loop end point belongs, and decompression parameters for decompressing the compression codes of a first portion having the loop start point or loop end point set at the enroute point thereof has same decompression parameters as are shared between said first portion and a second portion preceding or following said first portion, and
• wherein, when a part, following the loop start point or preceding the loop end point of said first portion having the loop start point or loop end point set at the enroute point thereof is to be read out with the readout address controlled by said loop control step, said decompression step uses the decompression parameters, to be used for decompression of the compression codes of said second portion preceding or following said portion, also for decompression of the compression codes of the part of said first portion.

A tone signal generation apparatus comprising:

• a memory storing a plurality of frames each including compression codes obtained by compressing waveform data over a portion thereof and decompression parameters for decompressing the compression codes of a next portion;
• said tone signal generation apparatus comprising:
• an address generation section that generates readout addresses in such a manner that the readout addresses vary at a rate corresponding to a pitch of a tone signal to be generated;
• a readout section that reads out data of the frames from said memory on the basis of the readout addresses generated by said address generation section;
• a section that takes out, from the data read out by said readout section, the decompression parameters included in each of the frames, the decompression parameters included in a given one of the frames becoming available upon completion of readout of all of the data included in the given frame;
• a decompression section that decompresses the compression codes of a particular portion included in any one of the frames read out by said readout section, on the basis of the decompression parameters of said particular portion having been included in a previously-read-out frame, to thereby reproduce a tone signal;
• and
• a loop control section that, on condition that the readout address has reached a loop end point, sets the readout address at a loop start point;
• and
• an output section that outputs a tone corresponding to the reproduced tone signal,
• wherein at least one of the loop start point and loop end point is set at an enroute point of the portion to which the loop start point or loop end point belongs, and decompression parameters for decompressing the compression codes of a first portion having the loop start point or loop end point set at the enroute point thereof has same decompression parameters as are shared between said first portion and a second portion preceding or following said first portion, and
• wherein, when a part, following the loop start point or preceding the loop end point of said first portion having the loop start point or loop end point set at the enroute point thereof is to be read out with the readout address controlled by said loop control section, said decompression section uses the decompression parameters, to be used for decompression of the compression codes of said second portion preceding or following said first portion, also for decompression of the compression codes of the part of said first portion.