Optimal bit allocations for lossless video coders: motion vectors vs. difference frames

We present a simple frame-adaptative procedure for minimizing the total rate in classical block based, motion-compensated lossless video coders. Our method can be applied to compress digital video for applications where no distortion is tolerated in the original video data. In motion-compensated video coding, motion vectors are used to improve the prediction of the current frame to be coded and must themselves be encoded with bits. We find an expression for the total rate of the current frame as a function of the number of bits allocated to the motion vectors. Then, we analytically derive the optimal motion bit allocations that minimize the total rate. We implement the video coder and present results on real video sequences, and discuss the potential applications of this work to the more interesting case of lossy video coding