The authors propose a high-performance hardware accelerator for intra prediction and mode decision in H.264/AVC video encoding. They use two intra prediction units to increase the performance. Taking advantage of function similarity and data reuse, the authors successfully reduce the hardware cost of the intra prediction units. Based on a modified mode decision algorithm, the design can deliver almost the same video quality as the reference software. The authors implemented the proposed architecture in Verilog and synthesized it targeting towards a TSMC 0.13mum CMOS cell library. Running at 75MHz, the 36K-gate circuit is capable of realtime encoding 720p HD (1280times720) video sequences at 30 frames per second (fps)