Patent ID: 8301439

Claim:
A method of encoding a low bit-rate audio signal, the method comprising: quantizing and encoding a plurality of first frequency sub-bands in a low frequency region of a full-band audio signal having a plurality of frequency sub-bands; generating a codebook of codevectors using one or more of the plurality of overlapping first frequency sub-bands of the low frequency region of the full-band audio signal to vector quantize at least one high frequency sub-band or to encode at least one high frequency sub-band by perceptual noise substitution; detecting an envelope of at least one second frequency sub-band in a high frequency region of the full-band audio signal higher than the highest low frequency sub-band and quantizing and encoding the envelope; selecting a codevector in the first frequency sub-band codebook that is most similar to the second frequency sub-band to be encoded from the generated codebook's codevectors and determining a codebook codevector index which defines a fine structure of the first frequency sub-band to help encode the structure of the similar second frequency sub-band; and generating a bit stream using encoded data generated in the encoding of the first frequency sub-band, the envelope, and the determined codebook codevector index.