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Robust MPEG-4 High-Efficiency AAC With Fixed- and Variable-Length Soft-Decision Decoding

MPEG-4 High-Efficiency advanced audio coding (HE-AAC) is optimized for low bit rate applications, such as digital radio broadcasting and wireless music streaming. In HE-AAC, the differential scale factors and quantized spectral coefficients are variable-length coded (VLC) by Huffman codes. The common reference value of the scale factors is a fixed-length coded global gain. Due to the error propagation in VLCs, a robust source decoder is desired for HE-AAC transmission over an error-prone channel. Unlike traditional hard-decision decoding or error concealment, soft-decision decoding utilizing bit-wise channel reliability information offers improved audio quality. In this work we apply soft-decision decoding of fixed length to the global gain and of variable length to the scale factors. Simulation results show a clearly improved performance.

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AES - Audio Engineering Society