An H.264 High-Profile Intra-Prediction with Adaptive Selection Between the Parallel and Pipelined Executions of Prediction Modes

A high-profile H.264 intra-frame encoder is suitable for low-cost and low-power applications and capable of providing enhanced compression efficiency. The high-profile is targeting the high-resolution videos. Thus, the encoding speed should be faster than or comparable to the baseline-profile. In previous work related to a hardware-based baseline-profile intra-frame encoder, a speed-up is achieved by the early termination of the intra modes and by an increase in the rate of hardware utilization only under one of the serialized and parallel schedules. This paper proposes a novel pipeline schedule for a hardware-based high-profile intra-prediction scheme in which the 8 × 8 prediction is performed in Stage 1 and 4 × 4, 16 ×16 and chroma predictions are executed during Stage 2. The processing time of Stage 2 is efficiently accelerated based on the result of the 8 × 8 prediction in Stage 1. According to the distribution of each mode, the schedule is adaptively selected between parallel and pipeline schedules. To increase the hardware utilization of the 8 × 8 prediction, the order of prediction modes and the inverse vertical transform is adaptively adjusted. In addition, early termination of the prediction modes is employed for a fast 8 × 8 prediction. The proposed 8 × 8 intra-prediction is implemented and verified as an entire intra-frame encoder. Experimental results show that the average number of cycles necessary to process one MB for videos with resolutions of 1920 ×1080 and 3840 × 2160 are only 269 and 253 cycles, respectively. Compared to JM13.2, the bitrate is increased by 1.13% on average with a small PSNR degradation of 0.06 dB. The difference in the rate-distortion performance between the proposed high-profile intra-prediction scheme and JM 13.2 is not significant, whereas the achieved speed-up due to the proposed schemes is considerable compared to the conventional hardware-based intra-prediction encoders.