This paper describes a bandwidth-efficient method for im-rnproved decoding of MPEG-AAC bitstreams when the en-rncoded data are transmitted over a noisy channel. Assum-rning that the critical part (headers) of each frame has beenrncorrectly received, we apply a soft-decoding method to re-rnconstruct the scalefactors, which represent a highly noise-rnsensitive part of the bitstream. The damaged spectral datarnare reconstructed using an intra-frame error concealmentrnmethod. Two methods for soft decoding of scalefactors arerndescribed: blind mode and informed mode. In the latter, arnvery small amount of additional data is included in the bit-rnstream. At medium SNR, this method provides a significantrnimprovement in perceptual signal quality compared to thernclassical hard-decoding method.
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