Hybrid variable length coding method and apparatus for video compression

Abstract

The invention discloses a hybrid variable length coding method and apparatus for video compression. The method is used for variable length coding an ordered series of digital signals, (e.g., of quantized transform coefficients of a block of image data with a most likely-to-occur amplitude, (e.g., 0), and at least one other amplitude, (e.g., 1)), to form a set of codewords. The method includes establishing a breakpoint (301) along the ordering to define a first contiguous region and a second contiguous region, such that clusters of consecutive signals of any value other than the most likely-to-occur value occur mostly in the first contiguous region. The method includes encoding the signals in the first region using a first region encoding method (303) suitable for encoding clusters; and encoding the signals in the second region using a second region encoding method (305). The first region and second region encoding methods include variable length codes such that relatively short codewords are formed to represent relatively more likely-to-occur sequences.

Description

[0001] This application is a divisional application of the patent application with the title of "Hybrid Variable Length Coding for Video Compression" and application number 200580019457.6 (PCT / US2005 / 020110) submitted on June 8, 2005. technical field [0002] The present invention relates to methods and devices for hybrid variable length coding for video compression. Background technique [0003] Two-dimensional variable-length coding (2D-VLC) involves collecting or assuming statistics of two-dimensional block transform coefficient events, where each event is a run of the most likely magnitude (eg 0) followed by another magnitude. Encoding includes assigning to each event a variable length code, for example an optimal code such as a Huffman code or an arithmetic code. In this specification, 0 is assumed to be the most likely magnitude. Gathering or assuming statistics includes tracking the magnitude of non-zero-valued coefficients being quantized and the number of zero-valu...

AI Technical Summary

Problems solved by technology

[0018] A disadvantage of 2D-VLC is that each non-zero-valued coefficient needs to be accompanied by a run-length code to identify its position, which run-length code takes the form of the number of preceding zero-valued coefficients

[0023] Therefore, it is still very inefficient to use this so-called "extended 2D-VLC method" in practice

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