Fast pipeline schedule for an H.264 intra frame encoder with early termination

This paper presents a fast H.264 intra frame encoder that processes an HD720p size video at 30 fps with the operating clock frequency of 40 MHz. The low clock frequency is achieved by a novel intra prediction schedule that employs pipelining of the 4 times 4 predictions and the early termination of 16 times 16 prediction. The pipelining is achieved by the optimal processing order for 4 times 4 predictions that reduces bubbles between consecutive 4 times 4 predictions. Execution cycles of 16 times 16 prediction are reduced by early termination which uses the cost of 4 times 4 prediction as the stop condition. With the proposed schedule, the execution time of 16 times 16 prediction is saved by 49% for intra prediction of HD720p size videos. For further speed-up, the two least probable modes among nine 4 times 4 prediction modes are excluded. As a result, the required execution time is reduced to 370 cycles which are about 61 cycles faster than the previous best implementation.