New Lookup Tables and Searching Algorithms for Fast H.264/AVC CAVLC Decoding

Abstract

In this paper, new codeword structures, tables, and searching methods for fast and efficient <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">coeff_token</emphasis> , <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">total_zeros</emphasis> , and <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">run_before</emphasis> decoding are developed. This new achievement is mainly based on the fact that the context-adaptive variable length coding (CAVLC) decoding can be modeled as a finite state machine. In order to quantitatively evaluate the proposed method in terms of decoding speed and complexity, we define the iteration bound <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\left({{1}\over {\mathtilde{\tau}}}\right)$</tex></formula> and the <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">complexity ratio</emphasis> <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(CR)$</tex></formula> . Using these gauge variables, we show that the new algorithms reduce <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\mathtilde {\tau}}$</tex></formula> to about one third and <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">complexity ratio</emphasis> to 0.95. This means that the proposed techniques reduce the decoding time to about one third and memory access count by 90% compared to those of the conventional methods without implementation overheads. Multiple-symbol parallel decoding method for <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">run_before</emphasis> syntax element is proposed based on a <emphasis emphasistype="italic" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bit-positioning</emphasis> with the critical path latency of only one multiplexer for the post-combination process. The proposed methods make it possible to implement a fast and efficient CAVLC decoding without losing video quality on any environments.