여기신호의 상관관계 기반 joint coding을 이용한 MPEG-4 audio lossless coding 인코더 복잡도 감소 방법

A Complexity Reduction Method of MPEG-4 Audio Lossless Coding Encoder by Using the Joint Coding Based on Cross Correlation of Residual

  • 조충상 (전자부품연구원 멀티미디어IP 연구센터) ;
  • 김제우 (전자부품연구원 멀티미디어IP 연구센터) ;
  • 최병호 (전자부품연구원 멀티미디어IP 연구센터)
  • Cho, Choong-Sang (Korea Electronics Technology Institute, Multimedia IP research center) ;
  • Kim, Je-Woo (Korea Electronics Technology Institute, Multimedia IP research center) ;
  • Choi, Byeong-Ho (Korea Electronics Technology Institute, Multimedia IP research center)
  • 투고 : 2009.11.05
  • 발행 : 2010.05.25

초록

오디오 신호를 무손실 압축하여 휴대용 멀티미디어 기기에서 최고의 오디오 품질을 제공하는 기기들이 등장하고 있으며, 무손실 오디오 압축을 위한 기술에서는 2006년 MPEG-4 audio lessless coding(ALS)와 MPEG-4 scalable lossless coding(SLS)가 국제 표준으로 채택 되었다. 2009년에는 MPEG에서 최대 스테레오 음원까지만 지원하는 MPEG-4 ALS simple profile을 정의하였다. 표준화된 무손실 오디오 코덱이 휴대용 멀티미디어 기기에서 널리 이용되기 위해서는 휴대용 멀티미디어 기기에서 가장 널리 쓰이는 스테레오 조건에서 낮은 복잡도를 보여야 한다. 하지만 기존 연구에서는 MPEG-4 ALS의 압축률을 향상시키거나, 혹은 다채널 환경에서의 복잡도를 개선하기 위한 연구들이 주로 이루어졌다. 본 논문에서는 MPEG-4 ALS 인코더의 복잡도와 압축률을 분석하고, 이를 바탕으로 MPEG-4 ALS simple profile 조건에서 MPEG-4 ALS 인코더의 복잡도를 개선하기 위한 방법을 제안한다. 분석 결과 MPEG-4 ALS 인코더의 analysis 블록에서 전체 복잡도의 75% 발생하므로, 기존의 연구에서 개발된 저 복잡도 필터를 인코더에 적용하여 복잡도를 감소시키며, joint coding의 압축 효율과 여기 신호의 상호상관계수의 관계를 기반으로 joint coding 결정 방법을 제안한다. 제안된 방법과 저 복잡도 필터가 포함된 MPEG-4 ALS 인코더의 성능은 MPEG-4 conformance test 파일과 일반 음악 파일을 이용하여 복잡도 및 압축률로써 평가된다. 실험 결과 제안된 방법이 적용되었을 경우 압축률은 유사하면서 인코더 복잡도가 24% 감소한다. 이를 통해 본 논문에서 제안된 방법이 MPEG-4 ALS 인코더의 복잡도 감소에 탁월한 성능을 가짐을 보였다.

Portable multi-media products which can service the highest audio-quality by using lossless audio codec has been released and the international lossless codecs, MPEG-4 audio lossless coding(ALS) and MPEG-4 scalable lossless coding(SLS), were standardized by MPEG in 2006. The simple profile of MPEG-4 ALS, it supports up to stereo, was defined by MPEG in 2009. The lossless audio codec should have low-complexity in stereo to be widely used in portable multi-media products. But the previous researches of MPEG-4 ALS have focused on an improvement of compression ratio, a complexity reduction in multi-channels coding, and a selection of linear prediction coefficients(LPCs) order. In this paper, the complexity and compression ratio of MPEG-4 ALS encoder is analyzed in simple profile of MPEG-4 ALS, the method to reduce a complexity of MPEG-4 ALS encoder is proposed. Based on an analysis of complexity of MPEG-4 ALS encoder, the complexity of short-term prediction filter of MPEG-4 ALS encoder is reduced by using the low-complexity filter that is proposed in previous research to reduce the complexity of MPEG-4 ALS decoder. Also, we propose a joint coding decision method, it reduces the complexity and keeps the compression ratio of MPEG-4 ALS encoder. In proposed method, the operation of joint coding is decided based on the relation between cross-correlation of residual and compression ratio of joint coding. The performance of MPEG-4 ALS encoder that has the method and low-complexity filter is evaluated by using the MPEG-4 ALS conformance test file and normal music files. The complexity of MPEG-4 ALS encoder is reduced by about 24% by comparing with MPEG-4 ALS reference encoder, while the compression ratio by the proposed method is comparable to MPEG-4 ALS reference encoder.

키워드

참고문헌

  1. T. Ricker, Zune vs. iPod specification smackdown, available at http://www.engadget.com/2007/10/03/zune-vs-ipo d-specification-smackdown/, Oct. 2007.
  2. ISO/IEC 14496-3:2005/Amd 2 : 2006, Information technology-Coding of audio-visual object, Part3: Audio Lossless Coding(ALS), new audio profiles and BSAC extensions, Mar. 2006.
  3. ISO/IEC 14496-3:2005/Amd 2 : 2006, Information technology-Coding of audio-visual object, Part3:Scalable Lossless Coding(SLS), June 2006
  4. Information technology-Coding of audio-visual simple profile and transport of SAOC, July 2009
  5. Y. Kamamoto, N. Harada, T. Moriya, "An efficient lossless compression of multichannel time-series signals by MPEG-4 ALS," in Proc. of ISCE2009, pp. 159-163,May 2009.
  6. Y. Kamamoto, N. Harada, and T. Moriya, "Multichannel Linear Prediction Method Compliant with the MPEG-4 ALS," in Proc. of IEICE Trans. Fundamentals, vol. E91, no. 3, pp. 756-762, Mar. 2008. https://doi.org/10.1093/ietfec/e91-a.3.756
  7. C. S. Cho, B. H. Choi, J. A. Kang, H. K. Kim, J. W. Lee, and S. P. Lee, " An efficient forward prediction order selection method for MPEG-4 audio lossless coding," in Proc. of AES 34th international conference, Aug. 2008.
  8. T. Liebchen, Y Reznik, T. Moriya, D.T. Yang, "MPEG-4 Audio Lossless Coding," in Proc. of 116th AES Convention, Preprint No. 6047, May 2004.
  9. T. Liebchen, T. Moriya, N. Harada, Y. Kamanoto, and Y. Reznik, "The MPEG-4 Audio Lossless Coding(ALS) Standarad-Technology and Applicantions," in Proc. of 119th AES Convention, Preprint No. 6589, Oct. 2005.
  10. Wai C. Chu, Speech Coding Algorithms Foundation and Evolution of Standardized coders,Wiley- Interscience 2003.
  11. F. Ghido, I. Tabus, "Adaptive design of the preprocessing stage for stereo lossless audio compression," in Proc. of 122nd AES Convention, Preprint No. 7085, May 2007.
  12. T. Liebchen, "An introduction to MPEG-4 audio lossless coding," in Proc. of ICASSP. 2004, vol.3, pp. 1012-1015, May 2004.
  13. T. Moriya, N. Harada, and Y. Kamamoty, "An enhanced encoder for the MPEG-4 ALS Lossless Coding standard," in Proc. of 121st AES Convention, Preprint No. 6869, Oct. 2006.
  14. N. Harada, T. Moriya, and Y. Kamamoto, "An implementation of MPEG-4 ALS standard compliant decoder on ARM core CPUs," in Proc. of 125th AES Convention, Preprint No. 7625, Oct. 2008.
  15. 조충상, 김제우, 신화선, 최병호, "MPEG-4 ALS 복호화기를 위한 고성능 필터링 방법," 2008년도 대한전자공학회 추계학술대회, 제31권 2호, pp. 741-742, Nov. 2008
  16. ISO/IEC 14496-4:2004/FDAM 19:2007(E), Informationtechnology - Coding of audio-visual objects - Part 4: Conformance testing, Amendment 19: Audio lossless coding (ALS), Apr. 2007.
  17. ITU-T Recommendation G.191, Software tools for speech and audio coding standardization, Oct. 2005.
  18. A. Zergaïnoh, P. Duhamel, and J.P. Vidal, "DSP implementation of fast FIR filtering algorithm using short FFT's,"in Proc. of ISCAS, vol. 1, pp. 219-222, May 1995.