Source model for transform video coder and its application. II. Variable frame rate coding

In the first part of this paper, we derived a source model describing the relationship between bits, distortion, and quantization step size for transform coders. Based on this source model, a variable frame rate coding algorithm is developed. The basic idea is to select a proper picture frame rate to ensure a minimum picture quality for every frame. Because our source model can predict approximately the number of coded bits when a certain quantization step size is used, we could predict the quality and bits of coded images without going through the entire real-coding process. Therefore, we could skip the right number of picture frames to accomplish the goal of constant image quality. Our proposed variable frame rate coding schemes are simple but quite effective as demonstrated by simulation results. The results of using another variable frame rate scheme, Test Model for H.263 (TMN-5), and the results of using a fixed frame rate coding scheme, Reference Model 8 for H.261 (RM8), are also provided for comparison