Perceptual-based coding mode decision
The framework of rate-distortion optimization (RDO) has been widely adopted for video coding to achieve a good trade-off between bit-rate and distortion. However, objective distortion metrics such as mean square error traditionally used in this framework are poorly correlated with perceptual video quality. To address this issue, we incorporate the structural similarity index as a quality metric into the framework and develop a predictive Lagrange multiplier selection technique to resolve the chicken-and-egg dilemma of perceptual-based RDO. The resulting perceptual-based RDO is then applied to H.264 intra mode decision as an illustration of the application of the proposed technique. Given a perceptual quality level, 5%–10% bit rate reduction over the JM reference software of H.264 is achieved. Subjective evaluation further confirms that, at the same bit-rate, the proposed perceptual RDO preserves image details and prevents block artifact better than the traditional RDO.