A key challenge to low-latency wireless video streaming, where persistent retransmission is impractical, is error control. While SP-frame adaptation of H.264 has potential to mitigate error propagation, streaming server is often either situated too far to react in a timely fashion to client feedbacks, or too computationally constrained to perform the necessarily complex adaptation simultaneously for multiple clients in different sessions. In this paper, we present an innovative error control mechanism using SP-frames of H.264 and performed by a network intermediary for video streaming to a wireless client. Using an intermediary means it is more responsive to client feedbacks due to its close proximity, and it can offload computation complexity from the streaming server. Simulation shows that about 2 dB improvement in PSNR is achievable for video streaming with low latency requirements over traditional schemes using I and P-frames only.