A new audio compression method based on a Spectral Oriented Tree is presented. After frequency transformation is performed over a frame of audio samples, the transform coefficients are arranged to form one to several quad trees depending on harmonic structures of the signal. In each quad tree, the coefficients having larger magnitudes regarded as more important are placed closer to the root position of the tree. A method called Concurrent Encoding In Descendant Tree (CEIDT) is employed to encode the tree coefficients such that those important coefficients are encoded before less important coefficients. Therefore, scalability is easy by discarding the tailing bits at any position of the bitstream. The quality is comparable to that of MP3. The proposed method doesn’t use psychoacoustic model and the computation complexity is relatively lower compared to those of MP3 and AAC. Only one small coding table is used for CEIDT method while the tables used in MP3 or AAC require lots of memory spaces. Thus, the proposed method provides a lower cost alternative, too.
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