Fast Bit Allocation Algorithms for Advanced Audio Coder
| Autor: | Chien-te Ho, 何建德 |
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| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 The MPEG Advanced Audio Coding (AAC) was first proposed in 1994. Its standard form is defined by the International Standards Organization. The High Efficiency AAC (HE AAC) combines two kinds of technologies, AAC and Spectral Band Replication (SBR). The version two High Efficiency AAC (HE AAC v2) further includes the third kind of technology, Parametric Stereo (PS). Two fast bit allocation algorithms based on psychoacoustic masking for determining scalefactors of the HE AAC v2 are proposed in this thesis. One is the One-Stage Fast Bit Allocation Algorithm called AAC 1-stage FBA. The other is the Two-Stage Fast Bit Allocation Algorithm referred to as AAC 2-stage FBA. The audio database used in the experiments is divided into 12 categories, including 9 kinds of musical instruments, symphony, and males and females singing. The experimental result shows that the AAC 1-stage FBA algorithm can reduce 48 % of the time consuming for scalefascors calculation. Both fast algorithms are also compared with other audio codecs, such as MP3, AC-3, and Ogg Vorbis. The objective and subjective tests show that the performance of the AAC 1-stage FBA algorithm is worse than that of MP3 when bit rates above 64 kbps. But it performs better than MP3 if bit rates below 64 kbps. Male singing and flute music are special cases for the AAC 1-stage FBA algorithm since it always performs better than MP3. The AAC 2-stage FBA algorithm performs graceful degradation of the HE AAC v2 for it is clearly superior to MP3 and AC-3 codecs at any bit rates in the experiments. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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