Temporal Noise Shaping with Companding

Arijit Biswas, Per Hedelin, Lars Villemoes and Vinay Melkote

Abstract:

Audio codecs are typically transform-domain based and efficiently code stationary musical signals but they struggle with speech and signals with dense transients such as applause. The temporal noise shaping (TNS) tool standardized in HE-AAC alleviates the issue of noise unmasking in these troublesome cases via signal-adaptive filtering of the transform domain quantization noise, albeit at the cost of significant additional side information in the bitstream. We present a novel alternative referred to as companding that involves QMF domain pre- and post-processing around the core transform-domain coding system: prior to transform encoding, the dynamic range of the signal is reduced locally within a QMF time slot and restored again post decoding, which naturally shapes the coding noise temporally. A primary advantage is that the companding function is fixed and hence enables signal-adaptive noise shaping with just 1-2 bits of side-information per frame. Subjective tests illustrate that the proposed tool improves the quality of hard-to-code applause excerpts compared to TNS while achieving comparable performance on speech signals. The coding tool described in this paper is part of the Dolby AC-4 audio coding system standardized by ETSI and included in ATSC 3.0.

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Cite as: Biswas, A., Hedelin, P., Villemoes, L., Melkote, V. (2018) Temporal Noise Shaping with Companding. Proc. Interspeech 2018, 3548-3552, DOI: 10.21437/Interspeech.2018-2096.

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BiBTeX Entry:

@inproceedings{Biswas2018,
author={Arijit Biswas and Per Hedelin and Lars Villemoes and Vinay Melkote},
title={Temporal Noise Shaping with Companding},
year=2018,
booktitle={Proc. Interspeech 2018},
pages={3548--3552},
doi={10.21437/Interspeech.2018-2096},
url={http://dx.doi.org/10.21437/Interspeech.2018-2096} }