Fuzzy Rate Controller for Variable Bitrate Video in Mobile Applications

In this paper we propose a low-complexity fuzzy video rate controller designed for real-time variable bitrate applications with buffer constraints. The algorithm is optimized for streaming application in mobile devices. Furthermore, the proposed algorithm can be used for local recording application so as the recorded video may be streamed in future. Today, many mobile phones include a digital camera that can be used to capture and encode video in real-time. We assume that no memory for storage of uncompressed video is available in mobile phones. Therefore, look-ahead and multi-pass rate controls are not possible. Furthermore, considering the processing power and, more importantly, battery life constraints in mobile devices, the proposed algorithm needs to be as simple as possible. The described variable bitrate (VBR) bit rate control algorithm controls the quantization scale (QS) on picture basis. The QS is mainly controlled by a fuzzy controller such that it minimizes the variation of QS to provide encoded video with high visual quality so as to utilize the variable bitrate benefits as much as possible. The proposed rate control algorithm (RCA) has been implemented in the MPEG-4, H.263 and H.264/AVC standard video codecs and the experimental results show that it provides high level average quality for encoded video while it strictly obeys buffering constraints.