Browsing by Author "Shih, Geng-Yu"

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Comparative study of audio spatializers for dual-loudspeaker mobile phones
(2007-01-01)
Bai, Mingsian R.
;
Shih, Geng-Yu
;
Lee, Chih-Chung
;
機械工程學系
;
Department of Mechanical Engineering
MPEG-1, layer 3 handsets equipped with dual loudspeakers and three-dimensional audio modules have received much attention in the market of consumer electronics. To create spatial impression during audio reproduction, the head-related transfer function (HRTF) and the crosstalk cancellation system (CCS) are key elements in many audio spatializers. However, there are many factors that one should take into account during the design and implementation stages of an audio spatializer in the handset application. In the paper, a comprehensive study was undertaken to compare various audio spatializers for use with dual- loudspeaker handsets, in the context of inverse filtering strategies. Two deconvolution approaches, the frequency-domain method and the time-domain method, are employed to design the required inverse filters. Different approaches to design audio spatializers with the HRTF, CCS, and their combination are compared. In particular, two modified CCS approaches are suggested. Issues in the implementation phase such as regularization, complex smoothing, and structures of inverse filters are also addressed in the paper. Comprehensive objective and subjective tests were conducted to investigate the aforementioned aspects of audio spatializers. The data obtained from the subjective tests are processed by using the multianalysis of variance to justify statistical significance of the results. (c) 2007 Acoustical Society of America.
Upmixing and downmixing two-channel stereo audio for consumer electronics
(2007-01-01)
Bai, Mingsian R.
;
Shih, Geng-Yu
;
Hong, Jhih-Ren
;
機械工程學系
;
Department of Mechanical Engineering
In this comprehensive study, algorithms for upmixing, downmixing, and joint up/downmixing are examined. Two upmixing algorithms are employed to convert two-channel stereo signals to five-channel signals. For downmixing, methods ranging from mixing with simple gain adjustment to more sophisticated Read Related Transfer Function (HRTF) filtering and Crosstalk Cancellation System (CCS) are utilized to downmix the center channel and the surround channels into the available two frontal loudspeakers. For situations where only two-channel content and loudspeakers are available, a number of up/downmixing schemes are used to simulate a virtual surround environment Emphasis of comparison is placed on a dual-loudspeaker MP3 handset. Listening tests are conducted to compare the processing methods in terms of three levels of subjective indices. The results are processed by using the Multivariate ANalysis Of VArianee (MANOVA) to justify the statistical significance.