SP and SI frames in the H.264 video coding standard can be used for error resilience, bitstream switching or random access. Despite a widespread interest in these new types of frames, no work so far has investigated, in a systematic way, their rate-distortion efficiency. In this paper, we propose a model for the rate-distortion performance of SI and SP frames. A comparison to experimental results, obtained with our implementation of an SP encoder, recently adopted by JVT, confirms its validity. The model predicts how the relative sizes of SP
and SI frames can be traded off. We analyze, both theoretically and experimentally, how this can be used to minimize the transmitted bit-rate when SP frames are used for video streaming with packet losses.