從高畫質的數位電視到個人隨身攜帶的手機，越來越多支援視訊播放功能的裝置已被人們廣泛使用，為讓視訊能更普遍地在各裝置間相互流傳，適當地調整視訊尺寸的大小以符合裝置的設定顯然是勢在必行。本論文提出以有限長度之升餘弦函數來作影像縮放的想法，並實證其效能優於傳統常用的雙立方、雙線性等函數。再者，本論文也針對影像縮減應用於H.264低位元率的情況作了分析，並得出將欲傳送的視訊縮減為原來一半再用H.264簡單畫面間預測模式編碼，其無論是在編碼時間或畫面品質的效能表現上都相當優異的結論。

More and more devices that support video broadcasting like high definition television (HDTV) or mobile handsets have gained popularity in the world. In order to enable multimedia content to transfer between networks and devices, video rescaling techniques are needed. In this paper, we propose to use truncated raised cosine function for video rescaling. Experimental results reveal that the performance of truncated raised cosine interpolator is superior to that of widely used interpolator like Bicubic or Bilinear. Furthermore, we discuss video downscaling influence under low bit rate constraint for H.264 CODEC. The result shows that downscaling video size to the half before encoding this video with simple H.264 inter prediction mode will get best performance when comparing to other combinations.

【1】“Draft ITU-T Recommendation and Final Draft International Standard of Joint Video Specification (ITU-T Rec. H.264 | ISO/IEC 144496-10 AVC),” Joint Video Team of ISO/IEC and ITU-T, March 2003.
【2】“Generic Coding of Moving Pictures and Associated Audio Information,” ISO/IEC 13818-2: Video (MPEG-2), May 1996.
【3】“Video Coding for Low Bit Rate Communication, Version 1,” ITU-T Recommendation H.263, 1995.
【4】“Coding of audio-visual objects - Part 2: Visual,” in ISO/IEC 14496-2 (MPEG-4 Visual Version 1), Apr. 1999.
【5】R.C. Gonzalez and R.E. Woods, “Digital Image Processing,” second edition, Prentice Hall, New Jersey, 2002.
【6】R. Dugad and N. Ahuja, “A Fast Scheme for Image Size Change in the Compressed Domain,” IEEE Trans. Circuits Syst. Video Technol., vol. 11, no. 4, pp. 461–474, Apr. 2001.
【7】H. Shu and L.P. Chau, “An Efficient Arbitrary Downsizing Algorithm for Video Transcoding,” IEEE Trans. Circuits Syst. Video Technol., vol. 14, no. 6, pp. 887–891, Jun. 2004.
【8】Y.S. Park and H.W. Park, “Arbitrary-Ratio Image Resizing Using Fast DCT of Composite Length for DCT-Based Transcoder,” IEEE Trans. Image Process., vol. 15, no. 2, pp. 494-500, Feb. 2006.
【9】Y.S. Park and H.W. Park, “Design and Analysis of an Image Resizing Filter in the Block-DCT Domain,” IEEE Trans. Circuits Syst. Video Technol., vol. 14, no. 2, pp. 274–279, Feb. 2004.
【10】Y.R. Lee and C.W. Lin, “Visual Quality Enhancement in DCT-Domain Spatial Downscaling Transcoding Using Generalized DCT Decimation,” IEEE Trans. Circuits Syst. Video Technol., vol. 17, no. 8, pp. 1079–1084, Aug. 2007.
【11】P. Thevenaz, T. Blu and M. Unser, “Image Interpolation and Resampling,” Swiss Federal Institute of Technology.
【12】J.V. VEGTE, “Fundamentals of Digital Signal Processing”, Prentice Hall, New Jersey, 2001.
【13】T.M. Lehmann, C. Gonner and K. Spitzer, “Survey: interpolation methods in medical image processing,” IEEE Trans. Med. Imag., vol. 18, no. 11, pp. 1049-1075, Nov. 1999.
【14】E.H.W. Meijering, K.J. Zuiderveld and M.A. Viergever, “Image reconstruction by convolution with symmetrical piecewise nth-order polynomial kernels,” IEEE Trans. Image Process., vol. 8, no. 2, pp. 192-201, Feb. 1999.
【15】K. Turkowski, “Filters for common resampling tasks,” Apple Computer, Apr. 1990.
【16】G. Ramponi, “Warped Distance for Space-variant Linear Image Interpolation,” IEEE Trans. Image Process., vol. 8, no. 5, pp. 629–639, May 1999.
【17】N.A. Dodgson, “Quadratic Interpolation for Image Resampling,” IEEE Trans. Image Process., vol. 6, no. 9, pp. 1322-1326, SEPT. 1997.
【18】R. Keys, “Cubic convolution interpolation for digital image processing,” IEEE Trans. Signal Process., vol. 29, no. 6, pp. 1153-1160, Dec. 1981.
【19】S.E. El-Khamy, M.M. Hadhoud, M.I. Dessouky, B.M. Salam and F.E.A. El-Samie, “A new edge preserving pixel-by-pixel (PBP) cubic image interpolation approach,” Proceeding of National Radio Science Conference, pp. C11-1-9, March 2004.
【20】J. Shi and S.E. Reichenbach, “Image interpolation by two-dimensional parametric cubic convolution,” IEEE Trans. Image Process., vol. 15, no. 7, pp. 1857-1870, July 2006.
【21】E. Meijering and M. Unser, “A note on cubic convolution interpolation,” IEEE Trans. Image Process., vol. 12, no. 4, pp. 477-479, April 2003.
【22】J. Shi and S.E. Reichenbach, “Interpolation by asymmetric, two-dimensional cubic convolution,” Proceeding of IEEE International Conference on Image Processing, vol. 2, pp. 994-997, Sept. 2005.
【23】S.E. Reichenbach and F. Geng, “Two-dimensional cubic convolution,” IEEE Trans. Image Process., vol. 12, no. 8, pp. 857-865, Aug. 2003.
【24】Joint Video Team software JM12.2 from
http://iphome.hhi.de/suehring/tml/download/
【25】H. Schwarz, D. Marpe and T. Wiegand, “Overview of the scalable video coding extension of the H.264 / AVC standard,” IEEE Trans. Circuits Syst. Video Technol., Vol. 17, No. 9, pp. 1103-1120, Sept. 2007.
【26】B. Girod, A. Aaron, S. Rane and D. Rebollo-Monedero, “Distributed video coding,” Proceedings of the IEEE, vol. 93, no 1, pp. 71-83, Jan. 2005.
【27】F. Brandi, R. de Queiroz and D. Mukherjee, “Super Resolution of Video Using Key Frames,” Proceeding of IEEE International Symposium on Circuits and Systems, pp. 1608-1611, May 2008.
【28】F. Brandi, R. de Queiroz and D. Mukherjee, “Super-resolution of Video Using Key Frames and Motion Estimation,” Proceeding of IEEE International Conference on Image Processing, pp. 321-324, Oct. 2008.
【29】D. Mukherjee, B. Macchiavelo and R. de Queiroz, “A simple reversed-complexity Wyner-Ziv video coding mode based on a spatial reduction framework,” Proceeding of IS&T/SPIE Symp. on Electronic Imaging, Visual Communications and Image Processing, pp. 65081Y1-65081Y12, Jan. 2007.
【30】W.T. Freeman, T.R. Jones and E.C. Pasztor, “Example-based super-resolution,” IEEE Comput. Graph. Appl., vol. 22, no.2, pp. 56-65, Mar./Apr. 2002.
【31】C. A. Segall, R. Molina and A. K. Katsaggelos, “High-resolution images from low-resolution compressed video,” IEEE Signal Process. Mag., vol. 20, pp. 37-48, May 2003.