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Quality Improvement of Low Bitrate HE-AAC using Linear Prediction Pre-processor  

Lee, Jae-Seong (연세대학교 전기전자공학부 디지털신호처리 연구실)
Lee, Gun-Woo (삼성전자)
Park, Young-Chul (연세대학교 컴퓨터통신공학부)
Youn, Dae-Hee (연세대학교 전기전자공학부 디지털신호처리 연구실)
Publication Information
The Journal of Korean Institute of Communications and Information Sciences / v.34, no.8C, 2009 , pp. 822-829 More about this Journal
Abstract
This paper proposes a new method of improving the quality of High Efficiency Advanced Audio Coding (HE-AAC). HE-AAC encodes input source by allocating bits for each scalefactor bands appropriately according to human ear's psychoacoustic property. As a result, insufficient bits are assigned to the bands which have relatively low energy. This imbalance between different energy bands can cause decreasing of sound quality like musical noise. In the proposed system, a Linear Prediction (LP) module is combined with HE-AAC as a pre-processor to improve sound quality by even bits distribution. To apply accurate human being's psychoacoustic property, the psychoacoustic model uses Fast Fourier Transform (FFT) spectrum of original input signal to make masking threshold. In its implementation, masking threshold of psychoacoustic model is normalized using the LP spectral envelope in prior to quantization of the LP residual. Experimental result shows that, the proposed algorithm allocates bits appropriately for insufficient bits condition and improves the performance of HE-AAC.
Keywords
Linear Prediction Pre-processor; Low Bitrate; HE-AAC; Spectral Hole;
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