We address the problem of delay-constrained streaming of multimedia packets over dynamic bandwidth channels. Efficient streaming solutions generally rely on the knowledge of the channel bandwidth, in order to select the media packets to be transmitted, according with their sending time. However, the streaming server usually cannot have a perfect knowledge of the channel bandwidth, and important packets may be lost because of over-estimation. We address the rate prediction mismatch by media scheduling with a conservative delay, which provides a safety margin for the packet delivery, even in the presence of unpredicted bandwidth variations. We formulate an optimization problem whose goal is to find the optimal conservative delay to be used in the scheduling process, given the network model and the playback delay imposed by the client. We then propose a simple solution to the scheduling delay estimation, effective in real-time streaming scenarios. Our streaming method proves robust against channel prediction errors, and performs better than other mechanisms based on frame reordering strategies.