| Summary: | 碩士 === 大同大學 === 通訊工程研究所 === 94 === Audio Lossless Coding is a new extension of MPEG-4 audio coding family. In December 27 2005, NTT Corp. has announced that an audio lossless coding technology was approved as an MPEG international standard specification dubbed“MPEG-4 ALS”. Partners in this standardization work included the Technical University of Berlin (Germany), RealNetworks Corp. (USA), and I2R (Singapore). The new emerging standard MPEG-4 ALS (Audio Lossless Coding) introduces an efficient lossless coding that enables the perfect reconstruction of the original signal and the compression of digital audio data without any loss in quality.
In this thesis our ongoing work develops adaptive estimated algorithms for two open designed parameters (block length switching and prediction order adaptation) in MPEG-4 ALS. About the block length switching, we get four best block length models from eight variable block length switching models from the first test, and design a adaptive estimated algorithm which has 95.12% for selecting best block length. About the prediction order adaptation, we propose a adaptive estimated algorithm which has 85.83% for selecting forward 3 best prediction order compared to the algorithm of prediction order full search from the experiment results. Finally, we apply the two adaptive estimated algorithms (block length switching with prediction order adaptation) in MPEG-4 ALS. Our proposed method can reduce 1.42% - 2.35% average compression ratio compared to the method of prediction order 6 + fixed block length 1000 – 4000. However, the computation load is still high, further improvement is expected.
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