Hierarchical Block Matching Algorithm (HBMA) for Motion Vector Estimation

The Hierarchical Block Matching Algorithm (HBMA) is an efficient motion estimation technique in video coding designed to reduce computational complexity while maintaining high motion vector prediction accuracy. Compared to traditional Exhaustive Block Matching Algorithm (EBMA), HBMA optimizes the search process through a hierarchical strategy, significantly reducing time complexity.

HBMA's core principle employs a "coarse-to-fine" search strategy. Initially, a broad-range coarse search is performed on lower-resolution pyramid layers to identify approximate motion directions. The algorithm then progressively refines the search to higher-resolution layers to enhance motion vector precision. This hierarchical approach effectively reduces the number of search points, avoiding the high computational overhead of EBMA which requires scanning all possible positions.

HBMA's advantages manifest in two key aspects: first, computational efficiency is substantially improved, making it particularly suitable for real-time video encoding scenarios; second, it maintains high motion estimation accuracy suitable for quality-sensitive applications. In contrast, while EBMA can achieve global optimal solutions, its excessive computational requirements make it impractical for real-time systems.

In implementation, HBMA typically integrates with image pyramid structures. The algorithm narrows down search ranges through different pyramid levels, ultimately achieving precise matching at the original resolution. This method is especially effective for complex motion scenarios, balancing computational resources and coding performance. Implementation typically involves building Gaussian/Laplacian pyramids and progressively refining motion vectors using reduced-search-window matching at each level.