針對以合成作分析架構下之ADPCM之研究

摘要適應性差分脈碼調變 (Adaptive differential pulse code modulation, ADPCM) 是目前常見的一種語音編碼方法。由於其編碼複雜度低，具有良好品質，以及適當的編碼率，因此常被使用在小型的內嵌播放系統當中。根據Shin及Kim的研究[5]，使用以合成作分析 (Analysis by Synthesis, ABS) 的方法，可以進一步改善ADPCM語音重建訊號的品質。在這篇論文中，我們針對以合成作分析架構下之ADPCM編碼加以研究，試圖尋找可以改善的極限，並提出實際可行的演算方法。我們將提出的演算方法應用在 ITU-T G.726 ADPCM 編碼器上，發現訊雜比可以改善高達10 dB。我們也發現，與Shin及Kim所提的方法相比，在相近的編碼複雜度下，我們所提的方法可以得到更好的編碼效能。關鍵詞：G.726、適應性差分脈碼調變、以合成作分析。

關鍵字

適應性差分脈碼調變；以合成作分析

並列摘要

Abstract Adaptive differential pulse code modulation (ADPCM) is widely used in a variety of audio signal compression playback systems because of its simplicity, good performance, and moderate bit rates. According to the study of Shin and Kim[5], the coding performance of ADPCM can be improved by using analysis by synthesis (ABS) technique. In this thesis, we focus on the topic of ADPCM combined with ABS framework. We study the performance limits and propose some adequate and practical algorithms. When applied to ITU-T G.726 ADPCM coder, we find the proposed algorithms can improve the output signal-to-noise ratio (SNR) up to 10 dB. In addition, when compared to the algorithm provided by Shin and Kim, our proposed algorithm can get better performances with similar coding complexities. Keyword : G.726、ADPCM、analysis-by-synthesis.

並列關鍵字

analysis by synthesis ； G.726 ； ADPCM

參考文獻

[1] ITU-T Recommendation G.711, Pulse Code Modulation (PCM) of Voice Frequencies, Nov. 1988.

[2] ITU-T Recommendation G.721, 32 kbit/s Adaptive Differential Pulse Code Modulation, Nov. 1988.

[3] ITU-T Recommendation G.726, 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM), 1990.

[5] Jong Won Shin and Nam Soo Kim, “Signal modification for ADPCM based on analysis-by-synthesis framework”, Signal Processing Letters, IEEE.pp. 177 – 179, March 2006.

[6] John Weily & Sons, “Speech coding algorithm” , WILEY INTERSCIENCE, 2003

國際替代計量

針對以合成作分析架構下之ADPCM之研究

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