Audio compression with non-uniform modulated complex lapped transform /
In the past 10 years, advances in audio compression have been tremendous. Lapped Orthogonal Transforms (LOT) and psychoacoustic properties have significantly improved performance of transform audio coders. As a result, standards like MP3 that satisfy low bit rates as well as high fidelity reproduc...
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| Format: | Thesis eBook |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Summary: | In the past 10 years, advances in audio compression have been tremendous. Lapped Orthogonal Transforms (LOT) and psychoacoustic properties have significantly improved performance of transform audio coders. As a result, standards like MP3 that satisfy low bit rates as well as high fidelity reproduction have recently emerged. However, pre-echoes subsist when processing transient sounds. This thesis describes a new audio coder, whose principal objective is to alleviate the pre-echo problem. This coder is based on the Non-uniform Modulated Complex Lapped Transform (NMCLT). This transform is derived from the modulated Lapped Orthogonal Transform (MLT). The NMCLT basis functions are designed such that they are devoid of time aliasing; they have a very good time localization, as well as desirable frequency resolution. Hence, implementing this transform in our coder should allow us to minimize pre-echoes. However, the major drawback of this transform is that over redundancies are introduced to reconstruct the original signal. We propose an encoding scheme that efficiently exploits this transform, and that also limits the bit rate by controlling redundancies and predicting some coefficients. Experimental results show that this coder considerably diminishes pre-echoes and that consequently the encoding quality of transient sounds is improved. Besides, the encoding quality of sounds that are not percussive is not really compromised. |
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| Item Description: | "Major subject: Electrical Engineering". Vita. |
| Physical Description: | xi, 62 : illustrations ; 28 cm. Also available online. Issued also on microfiche from Lange Micrographics. |
| Bibliography: | Includes bibliographical references (leaves 60-61). |