This paper presents a flexible block processing order, called split unit coding order (SUCO), for video coding. In the conventional block-based image and video compression, the largest blocks are processed in a raster scan order while further partitioned blocks are processed in a z-scan order. Due to the fixed coding order, the information that can be exploited for prediction at coding block is limited to the left and above neighbors. Beyond the traditional prediction from left and above, the proposed SUCO allows more flexible processing order for the partitioned blocks so that the coding blocks could also utilize right neighboring information, such as reconstructed pixels and motion information, more adaptively. The impact of proposed coding order has been verified in the several video coding platforms: 2.1% and 2.1% BD-rate reduction on average in AI and RA configuration over HM12.1; 1.6% BD-rate reduction on average in RA over JEM3.1; 1.0% BD-rate reduction on average in RA over ETM4.1.

https://ieeexplore.ieee.org/document/9428179