An advanced hierarchical motion estimation scheme with lossless frame recompression for ultra high definition video coding

In this paper, a hardware-efficient fast algorithm with a lossless frame recompression scheme for large search range (SR) motion estimation (ME) utilized in ultra high definition video encoder is presented. To ensure high ME quality for hierarchical motion search, the advanced hierarchical ME scheme which processes the multi-resolution search with a coarse-to-fine strategy in parallel is proposed. This enables high data and hardware reuse for much lower bandwidth and memory cost, which at the same time maintains ME quality. Furthermore, a lossless frame recompression scheme based on this ME algorithm to further reduce DRAM bandwidth is presented. An efficient leveling memory organization as well as a leveling two-step data fetching strategy is proposed to meet constrains of random access for hierarchical motion search structure. Experimental results show that the total scheme increases PSNR by an average of 0.03dB with a much less bit rate increasing compared with previous works especially for high motion sequences, while achieving a considerable saving of memory and bandwidth cost for large SR of [-128, 127].