Real-time VBR rate control of MPEG video based upon lexicographic bit allocation

The MPEG-2 video standard describes a bitstream syntax and a decoder model but leaves many details of the encoding process unspecified, such as encoder bit rate control. The standard defines a hypothetical decoder model, called the video buffering verifier, that can operate in either constant-bit-rate or variable-bit-rate modes. We present a low-complexity algorithm for variable-bit-rate control suitable for low-delay, real-time applications. The algorithm is motivated by recent results in lexicographic bit allocation. The basic algorithm switches between constant-quality and constant-bit-rate modes based on changes in the fullness of the decoding buffer in the video buffering verifier. We show how the algorithm can be applied either to produce a desired quality level or to meet a global bit budget. Simulation results show that the algorithm compares favorably to the optimal lexicographic algorithm.