Energy-efficient SATD for beyond HEVC

State-of-the-art video coding standards adopt large block and transform sizes. Moreover, as resolutions keep growing, there is a trend in adopting even larger structures in future video encoders, resulting in higher complexity. Therefore, the design of energy-efficient architectures for variable block size distortion metrics are key to keep the energy requirements of battery devices under a reasonable budget. The Hadamard-based Sum of Absolute Transformed Differences (SATD) is used as distortion metric in several steps of encoding, increasing the overall encoding efficiency at the cost of rising complexity. In this work, we propose two main approaches for SATD calculation of N × N block sizes. One using a Transpose Buffer (TB) and another one using a Linear Buffer (LB). Furthermore, we synthesized four sizes (4 × 4 up to 32 × 32) of each main SATD architecture to evaluate their area and energy estimates. The results show a large increase in area for TB-SATD, while LB-SATD area increases in a much smaller pace. On the other hand, the TB-SATD synthesized for Low-Vdd/High-Vt show up to be the most energy-efficient architectures for all sizes.