Bandwidth extension method, bandwidth extension apparatus, program, integrated circuit, and audio decoding apparatus

摘要

To provide a bandwidth extension method which allows reduction of computation amount in bandwidth extension and suppression of deterioration of quality in the bandwidth to be extended. In the bandwidth extension method: a low frequency bandwidth signal is transformed into a QMF domain to generate a first low frequency QMF spectrum; pitch-shifted signals are generated by applying different shifting factors on the low frequency bandwidth signal; a high frequency QMF spectrum is generated by time-stretching the pitch-shifted signals in the QMF domain; the high frequency QMF spectrum is modified; and the modified high frequency QMF spectrum is combined with the first low frequency QMF spectrum.

主权项

1. A bandwidth extension method for producing a full bandwidth signal from a low frequency bandwidth signal, the low frequency bandwidth signal being an audio signal, said method comprising:
transforming the low frequency bandwidth signal into a quadrature mirror filter bank (QMF) domain to generate a first low frequency QMF spectrum; generating a low order harmonic patch by time-stretching the low frequency bandwidth signal by transforming the low frequency bandwidth signal into a second low frequency QMF spectrum having finer frequency resolution than the first low frequency QMF spectrum; generating signals that are pitch shifted, by applying different shift coefficients to the low order harmonic patch, and generating a high frequency QMF spectrum from the signals; and generating the full bandwidth signal by combining the high frequency QMF spectrum with the first low frequency QMF spectrum.