Customization of de-blocking filter edge order for high performance: Study of H.264 AVC/SVC, H.265

Abstract

Transformation and quantization in block based video codecs introduces blocking artifacts at edges. Special optimized video filter called de-blocking filter is applied on 4x4/ 8x8 block boundary to enhance visual quality and improve prediction efficiency. Most of the recent video codecs, H.264, H.265 (HEVC), VC-1 uses in-loop de-blocking (LPF) filter in decoder path. Each video codec standard defines fixed order of filter operation to have consistency in universal decoder output. Standard defined fixed edge order is not optimal for various architectures of de-blocking Hardware Accelerator (HWA), as it will have to compromise on performance, power or area. Pipelining of unfiltered pixel loading with filter operation, internal storage to keep partially or fully filtered pixels and order of storage of fully filtered pixels are some of the challenges that are difficult to meet with standard defined edge order. In this paper, a novel approach of customizing edge order is discussed for differing architectural requirements and for various video codec standards. Resultant filtered data with optimized edge order matches that of with standard defined edge order.