A sliding window approach to real-time H.263+ frame rate adjustment

H.263+ is an emerging video compression standard for the low bit rate visual communication. Up to now, most H.263+ rate control algorithms, especially that in the test model of the near-term (TMN), focus on macroblock level bit allocation and low latency under a constant-frame-rate and constant-bit-rate (CBR) channel. As expected, these algorithms are not capable of handling the transmission bandwidth fluctuation and the video quality can be degraded seriously. We propose a new H.263+ rate control scheme which supports the variable bit rate (VBR) channel through the frame rate adjustment. In particular, a fast realization of encoding frame rate control based on motion information within the sliding window is developed to efficiently pursue the tradeoff between spatial/temporal qualities. Experimental results are provided to demonstrate the superior performance of the proposed scheme.