Using the perceptual distortion metric returned by the psychoacoustic module, conventional bit allocation schemes operate iteratively to maintain equal perceptual distortion in all critical bands. For codecs employing uniform quantization schemes, this paper proposes a new approach to determine the optimal MNR (Mask to Noise Ratio) levels for the critical bands. The scheme exploits the fact that the quantizer used is uniform in nature and all critical bands are equally distorted, to arrive at a non-iterative solution. Additionally, this method is independent of the target bit-rate. The proposed scheme achieves a 2-3x reduction in the complexity of the quantization block. An example application for this scheme is given with reference to the MPEG-2 Layer 1 and 2 encoder.

Authors: Konda, Preethi; Prakash, Vinod
Affiliation: Ittiam Systems Pvt. Ltd, Bangalore, Karnataka, India
AES Convention: 116 (May 2004) Paper Number: 6172
Publication Date: May 1, 2004
Subject: Low Bit-Rate Audio Coding

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