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Open Access Research Article

Motion Compensation on DCT Domain

Ut-Va Koc1* and KJ Ray Liu2

Author Affiliations

1 Lucent Technologies Bell Labs, 600 Mountain Avenue, Murray Hill, NJ 07974, USA

2 Department of Electrical and Computer Engineering and Institute for Systems Research, University of Maryland, College Park, MD 20742, USA

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EURASIP Journal on Advances in Signal Processing 2001, 2001:291206  doi:10.1155/S1110865701000245


The electronic version of this article is the complete one and can be found online at: http://asp.eurasipjournals.com/content/2001/3/291206


Received:21 May 2001
Revisions received:21 September 2001
Published:2 October 2001

© 2001 Koc and Liu

Alternative fully DCT-based video codec architectures have been proposed in the past to address the shortcomings of the conventional hybrid motion compensated DCT video codec structures traditionally chosen as the basis of implementation of standard-compliant codecs. However, no prior effort has been made to ensure interoperability of these two drastically different architectures so that fully DCT-based video codecs are fully compatible with the existing video coding standards. In this paper, we establish the criteria for matching conventional codecs with fully DCT-based codecs. We find that the key to this interoperability lies in the heart of the implementation of motion compensation modules performed in the spatial and transform domains at both the encoder and the decoder. Specifically, if the spatial-domain motion compensation is compatiable with the transform-domain motion compensation, then the states in both the coder and the decoder will keep track of each other even after a long series of P-frames. Otherwise, the states will diverge in proportion to the number of P-frames between two I-frames. This sets an important criterion for the development of any DCT-based motion compensation schemes. We also discuss and develop some DCT-based motion compensation schemes as important building blocks of fully DCT-based codecs. For the case of subpixel motion compensation, DCT-based approaches allow more accurate interpolation without any increase in computation. Furthermore, a scare number of DCT coefficients after quantization significantly decreases the number of calculations required for motion compensation. Coupled with the DCT-based motion estimation algorithms, it is possible to realize fully DCT-based codecs to overcome the disadvantages of conventional hybrid codecs.

Keywords:
video codec; video coding; MPEG compatibility; motion compensation; DCT

Research Article