MPEG-4無失真音訊編碼之適應性分析

PARAMETER ADPATATION ANALYSIS FOR MPEG-4 AUDIO LOSSLESS CODING

蔡長運(Chang-Yun Tsai)

指導教授 ： 李清坤

大同大學/電機資訊學院/通訊工程研究所/碩士(2007年)

摘要

近年來音樂的品質漸漸受到重視，能享受到高音質的音樂族群已逐漸浮現。高音質意味著對於數位語音訊號是在完全不失真的情況之下所呈現的音質，而在有限的資源下，語音壓縮勢在必行，也就代表著無失真的語音壓縮(ALS)，可以帶來原音重現的效果。
本篇論文主要研究的工作是對於MPEG-4 ALS 標準中開放設計的兩項參數調整機制，亦即區塊長度轉換﹙block length switching﹚和預估器調整﹙prediction﹚發展出適應性估測機制。論文中對於MPEG-4可以調整的部份做適應性調整，在適應性區塊長度轉換﹙adaptive block length switching﹚中對於每一個區塊給予不同的長度，並選取最佳的長度使用，而在適應性階數預估器調整﹙adaptive order linear prediction﹚中對於每一段給予不同的階數，並選取最佳的階數，對於適應性的判斷原本應在從壓縮比來做大小的比較，而在此則是運用預估器中的預估誤差( prediction error )取絕對平均值( RMS )比較大小，我們稱之為提前適應性階數預估器調整﹙forward-adaptive prediction order ﹚，此方式對於運算複雜度上有非常顯著的幫助，雖然對於壓縮率而言會這種方式會有少許的增加，但運算複雜度上可以節省將近三倍以上的運算量，這樣的方法在開放的MPEG-4 ALS 標準中將會是一種非常有效率的音訊無失真壓縮的設計。

關鍵字

適應性 ； 無失真編碼 ； 音訊

並列摘要

Recent years have seen increased attention being given to high quality of digital product. In high quality of music the lossless digital audio provide a good performance. The Audio Lossless Coding (ALS) has achieves reconstruction without loss any quality and already developed period of time. However, there is very limited study on lossless coding in the literature. Although few work has been done to date, more studies need to be conducted to ascertain the effects of improve compression rate and complex of lossless coding.
The purpose of the research presented in this article is to analysis the two open designed parameters of block lengths switching and prediction in MPGE-4 standard. In this paper develops adaptive estimated algorithms for two parameters to adaptive block lengths switching and adaptive order linear prediction. The results show that adaptive block lengths switching and adaptive order linear prediction to improve compression rate and complex were significantly related, overall have been very positive. These findings are in line with previous studies, although no previous study has asked this question in detail. Show the method that we designed. It is a kind of efficient method of the audio lossless compression.

並列關鍵字

adaptation ； lossless coding ； audio

參考文獻

[1] Y. A. Reznik, “Coding of prediction residual in MPEG-4 standard for lossless audio coding (MPEG-4 ALS),” ICASSP 2004, pp. 1024-1027.

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[11] T. Liebchen and Y. A. Reznik, “MPEG-4 ALS: an Emerging Standard for Lossless Audio Coding,” Proc. IEEE Data Compression Conference, 2004, pp. 439-448.

[12] T. Liebchen, Y. Reznik, T. Moriya, and D. T. Yang, “MPEG-4 Audio Lossless Coding,” 116th AES Convention, 2004, no. 6047, pp. 1-9.