Reversible 2-dimensional pre-/post-filtering for lapped biorthogonal transform

Abstract

An efficient lapped transform useable in digital media codecs is realized using a reversible 2-dimensional overlap operator for pre / post filtering that is applied on a staggered grid relative to a core transform. The 2-dimensional lapped operator is based on a separably applied 1-dimensional reversible lapped operator, which is re-arranged as a sequence of elementary transforms in interleaved stages on subsets of points of the respective block and further implemented in lifting steps for computational efficiency. The interleaved stages include applying rotation and scaling stages between initial and final stages involving a normalized 2x2 Hadamard transform

Description

[0001] Related application information [0002] This application is a continuation-in-part of U.S. Patent Application Serial No. 11 / 015,148, filed December 17, 2004, by Tu et al., entitled "Reversible Overlap Operator For Efficient Lossless Data Compression" , which application is hereby incorporated by reference. technical field [0003] The present invention generally relates to compression of digital media (eg, video and images) using lapped transforms. Background technique [0004] overlap transform [0005] The lapped transform is a powerful signal processing technique for data compression. See, eg, Signal Processing with Lapped Transforms by H.S. Malvar, Boston, MA: Artech House, 1992. However, to date, an efficient lapped transform with linear phase has never been formulated or applied for lossless (reversible) data compression. [0006] As discussed in more detail below, it is known that a lapped transform can be formulated as a pre-filter followed by a data tran...

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Besides that, both techniques are computationally expensive

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