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Multi-frame AR model을 이용한 LPC 계수 양자화
정원진,김무영,Jung, Won-Jin,Kim, Moo-Young 한국음향학회 2012 韓國音響學會誌 Vol.31 No.2
음성코딩 시 성도는 Linear Predictive Coding (LPC) 계수를 이용해서 모델링 한다. 일반적으로 LPC 계수는 양자화와 선형보간 관점에서 유리한 Line Spectral Frequency (LSF) 파라미터로 변경하여 사용한다. 10차 이상의 다차원 LSF 데이터를 벡터 양자화를 이용하여 직접 코딩하게 되면 벡터 내 상관관계 (intra-frame correlation)를 모두 이용할 수 있으므로 rate-distortion 관점에서는 높은 효율을 기대할 수 있다. 하지만, 계산량과 메모리 요구량이 높아져서 실제 코딩 시스템에서는 사용할 수 없게 되므로, 차원을 나누어 압축하는 Split Vector Quantization (SVQ)이 이용된다. 또한, LSF 데이터는 과거 벡터와의 벡터 간 상관관계 (inter-frame correlation)가 높으므로, 이를 이용한 Predictive Split Vector Quantization (PSVQ)이 사용되고 있다. PSVQ는 SVQ 보다 높은 rate-distortion 성능을 보인다. 본 논문에서는 음성 저장 장치를 위한 최적의 PSVQ를 구현하기 위해서 다수의 과거 프레임 정보와의 벡터 간상관관계 (inter-frame correlation)를 고려한 Multi-Frame AR-model 기반 SVQ (MF-AR-SVQ)를 제안하였다. 기존 PSVQ와 비교해 보았을 때, MF-AR-SVQ는 계산량과 메모리 요구량의 큰 증가 없이, 평균 spectral distortion 관점에서 약 1비트의 성능 향상을 보였다. For speech coding, a vocal tract is modeled using Linear Predictive Coding (LPC) coefficients. The LPC coefficients are typically transformed to Line Spectral Frequency (LSF) parameters which are advantageous for linear interpolation and quantization. If multidimensional LSF data are quantized directly using Vector-Quantization (VQ), high rate-distortion performance can be obtained by fully utilizing intra-frame correlation. In practice, since this direct VQ system cannot be used due to high computational complexity and memory requirement, Split VQ (SVQ) is used where a multidimensional vector is split into multilple sub-vectors for quantization. The LSF parameters also have high inter-frame correlation, and thus Predictive SVQ (PSVQ) is utilized. PSVQ provides better rate-distortion performance than SVQ. In this paper, to implement the optimal predictors in PSVQ for voice storage devices, we propose Multi-Frame AR-model based SVQ (MF-AR-SVQ) that considers the inter-frame correlations with multiple previous frames. Compared with conventional PSVQ, the proposed MF-AR-SVQ provides 1 bit gain in terms of spectral distortion without significant increase in complexity and memory requirement.
모바일 쇼핑몰의 지각된 정보품질이 스마트폰 사용자의 쇼핑몰 사용의도에 미치는 영향
정원진 ( Won Jin Jung ) 한국정보시스템학회 2012 情報시스템硏究 Vol.21 No.3
There has been an upward trend in smartphone sales in Korea as well as the rest of the world. Even though smartphones are now at the peak of their popularity, the fact that they are somewhat limited in terms of their usages for certain purposes is unexpected. Precisely, compared to PC, smartphones typically have smaller display screens with a lower resolution, which make them difficult to use in general. For instance, when customers search the information about products in mobile shopping malls, due to the smaller screen with a low resolution smartphone users may realize that it is not easy and convenient not only to search the information, but also to read the information they found in the shopping malls. This restriction could become one of reasons that lowers the perceived quality of information in the shopping malls, which in turn leads to the reluctance to use the shopping malls. A comprehensive information systems (IS) literature review found that there has been little empirical evidence on perceived information quality that affects smartphone users` intention to use mobile shopping malls. The purposes of this study is to examine 1) the effects of perceived information quality on smartphone users` intention to use mobile shopping malls and 2) the relationships among behavioral beliefs in the middle of independent and dependent variables, such as information satisfaction, perceived usefulness, and customers` attitude toward mobile shopping. A survey was conducted in March 2012. College students and practitioners took participated in the survey. Structural Equation Modeling(SEM) was used for all data analysis. The results found that there is a strong relationship between perceived information quality and smartphone users` intention to use mobile shopping malls. In addition, this study also showed that there are strong relationships among behavioral beliefs. Further research is expected to validate the findings of this study and apply them in specific contexts.