Idempotent H.264 intraframe compression

This paper studies H.264 intraframe multi-generation characteristics and presents four mechanisms that contribute to the generation degradation. We analyze the H.264 transform and quantization and reveal that for some quantization parameters there always exists at least one clipping compensation matrix to make the H.264 intraframe multi-generation coding idempotent as long as the same prediction mode and the same quantization parameter are selected for each coding generation. In addition, an idempotent H.264 intraframe multi-generation coding procedure is presented. The procedure has three additional steps to achieve idempotence: Prediction Mode and QP Restriction, Prediction Mode and QP Identification, and Clipping Compensation. Experiment results show that the proposed idempotent coding produces no generation PSNR loss and the rate-distortion efficiency is almost same as that of traditional H.264.