Rate control of a region-based H.263 video codec under time-varying channels
A region-based video codec based on the H.263+ standard is examined and its associated novel rate control schemes are proposed for visual communication through time-varying low-bit-rate channels. The region-based coding scheme is a hybrid method that consists of the traditional block DCT coding and the object-based coding. Basically, we adopt H.263+ as the platform, and develop a fast macroblock-based segmentation method to implement the region-based video codec. The proposed rate control solution includes rate control in three levels: encoding frame selection, frame-layer rate control and macroblock-layer rate control. The goal is to enhance the visual quality of decoded frames without obvious motion unsmoothness under time-varying channels. The efficiency of the proposed rate control schemes applied to the region-based video codec is demonstrated via several typical test sequences.