Frame skipping minimization in low bit-rate video coding

Abstract

When encoding low bit-rate video at constant bit-rate, state of the art video encoders may be forced to skip frames. Frames are mostly skipped after "scene changes", i.e. immediately after the beginning of a new scene. We address the problem of determining the minimal number and the exact positions of the frames that must be skipped in a video sequence in order to match closely a prefixed rate and distortion. The reduction of the number of skipped frames decreases the jerkiness associated to the skips and improves the overall quality of the encoded video. The off-line frame-layer rate control method we propose can be used in several existing video coders and it is fully compatible with rate-distortion optimized macroblock-layer rate controls. We also present a simplified heuristic that performs almost optimally while requiring only minimal encoding complexity with respect to the standard encoders.