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Quality Improvement of Low-Bitrate HE-AAC Encoder  

Kim, Jeong-Geun (연세대학교 전기전자공학부 디지털신호처리연구실)
Lee, Jae-Seong (연세대학교 전기전자공학부 디지털신호처리연구실)
Lee, Tae-Jin (전자통신연구원 방송미디어연구그룹)
Kang, Kyeong-Ok (전자통신연구원 방송미디어연구그룹)
Park, Young-Cheol (연세대학교 컴퓨터정보통신공학부)
Publication Information
The Journal of the Acoustical Society of Korea / v.27, no.2, 2008 , pp. 66-74 More about this Journal
Abstract
In this paper, we propose new techniques that can improve the quality of AAC and SBR encoders comprised in low bitrate HE-AAC. To reduce the pre-echo artifacts often occurring for transient blocks in AAC, we propose an extended Temporal Noise Shaping (sTNS) in which the frequency range is selectively extended down to the low-frequency region. Also, for he high-frequency region being coded by SBR encoder, tones are identified through a sinusoidal modeling and their frequencies are adjusted within the QMF band in order to reduce the noise floor due to aliasing. Spectrograms of the decoded signals were compared and listening tests were conducted to evaluate the proposed algorithm. Results confirmed the effectiveness of the proposed algorithm.
Keywords
HB-AAC; TNS; Sinusoidal model; AAC; SBR; Pre-echo; Musical noise;
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