Methods of efficiently recording an audio signal in semiconductor memory

A method of decoding an audio signal, hierarchically encoded by,

• (a) digitizing the audio signal, and
• (b) hierarchically encoding the digitized audio signal, step (b) including the substeps of,
• (1) encoding a relatively lowest hierarchical level with a first number of bits, from a first portion of the digitized audio signal below a first predetermined frequency, and
• (2) encoding a relatively higher hierarchical level with a second number of bits, greater than the first number of bits, from a portion of the digitized audio signal below a second predetermined frequency greater than the first predetermined frequency, the encoded relatively higher hierarchical level further excluding the encoded first portion of the digitized audio signal, the method of decoding comprising the steps of:
• (a) identifying the first number of bits of the relatively lowest hierarchical level and the second number of bits of the relatively higher hierarchical level;
• (b) decoding the encoded relatively lowest hierarchical level based upon the identified first number of bits;
• (c) decoding the encoded relatively higher hierarchical level based upon the identified second number of bits;
• and
• (d) converting the decoded relatively lowest and higher hierarchical levels of steps (b) and (c) into an audio signal.

A decoder for decoding an audio signal, hierarchically encoded by an encoder including,

• a first device for digitizing an audio signal into frequency coefficients,
• a bit allocator for determining a number of bits to be allocated for encodation in each of a plurality of hierarchical levels based upon the frequency coefficients;
• and
• a hierarchical quantizer for encoding a relatively lowest hierarchical level of a first number of bits, based upon the determined allocation, from a first portion of the digitized audio signal below a first predetermined frequency, and for encoding a relatively higher hierarchical level with a second number of bits, based upon the determined allocation and greater than the first number of bits, from a portion of the digitized audio signal below a second predetermined frequency greater than the first predetermined frequency, the encoded relatively higher hierarchical level further excluding the encoded first portion of the digitized audio signal, the hierarchical decoder comprising:
• first means for identifying the first number of bits of the relatively lowest hierarchical level and the second number of bits of the relatively higher hierarchical level;
• second means for decoding the encoded relatively lowest hierarchical level based upon the identified first number of bits and for decoding the encoded relatively higher hierarchical level based upon the identified second number of bits;
• and
• third means for converting the decoded relatively lowest and higher hierarchical levels into an audio signal.