Energy and area-efficient hardware implementation of HEVC inverse transform and dequantization

High Efficiency Video Coding (HEVC) inverse transform for residual coding uses 2-D 4×4 to 32×32 transforms with higher precision as compared to H.264/AVC´s 4×4 and 8×8 transforms resulting in an increased hardware complexity. In this paper, an energy and area-efficient VLSI architecture of an HEVC-compliant inverse transform and dequantization engine is presented. We implement a pipelining scheme to process all transform sizes at a minimum throughput of 2 pixel/cycle with zero-column skipping for improved throughput. We use data-gating in the 1-D Inverse Discrete Cosine Transform engine to improve energy-efficiency for smaller transform sizes. A high-density SRAM-based transpose memory is used for an area-efficient design. This design supports decoding of 4K Ultra-HD (3840×2160) video at 30 frame/sec. The inverse transform engine takes 98.1 kgate logic, 16.4 kbit SRAM and 10.82 pJ/pixel while the dequantization engine takes 27.7 kgate logic, 8.2 kbit SRAM and 1.10 pJ/pixel in 40 nm CMOS technology. Although larger transforms require more computation per coefficient, they typically contain a smaller proportion of non-zero coefficients. Due to this trade-off, larger transforms can be more energy-efficient.