High-quality audio transform coding at 128 kbits/s

An approach to wideband digital audio compression of CD-quality signals at data rates of 128 kb/s channel and below is presented. A form of adaptive transform coding, this technique features a nonuniform frequency division and coding scheme to exploit known characteristics of human perception. The algorithm has low computational complexity and can be adapted for use at other bit rates. A windowed overlap-add process is used with the forward/inverse transforms, which have been efficiently implemented using FFTs. Transform coefficients are converted into a subband block-companded format consisting of exponent words and associated mantissas, which are then coded with an adaptive quantizer. A real-time, single-chip programmable digital signal processing (DSP) implementation encodes 480-kHz-sampled stereo audio signals at a variety of bit rates. At 128 kb/s, the coder's subjective performance is appropriate for highest-quality 15-kHz professional audio applications.<
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