Real-Time Frame-Layer H.264 Rate Control for Scene-Transition Video at Low Bit Rate

An abrupt scene-transition frame is one that is hardly correlated with the previous frames. In that case, because an intra-coded frame has less distortion than an inter-coded one, almost all macroblocks are encoded in intra mode. This breaks up the rate control flow and increases the number of bits used. Since the reference software for H.264 takes no special action for a scene-transition frame, several studies have been conducted to solve the problem using the quadratic R-D model. However, since this model is more suitable for inter frames, they are unsuitable for computing the QP of the scene-transition intra frame. In this paper, a modified algorithm for detecting scene transitions is presented, and a real-time rate control scheme accounting for the characteristics of intra coding is proposed for scene- transition frames. The proposed scheme was validated using 16 test sequences. The results showed that the proposed scheme performed better than the existing H.264 rate control schemes. The PSNR was improved by an average of 0.4-0.6 dB and a maximum of 1.1-1.6 dB. The PSNR fluctuation was also improved by an average of 18.6 %.¹