The stream manager should have already buffered the stream a little bit before it is asked for data. Whenever the sound engine asks for data, and the stream manager has no data ready, there will be a starvation: you may hear a gap in audio, tracks in music segments may be de-synchronized, and a source starvation error notification will be sent to the authoring tool. (They appear in yellow in the capture log. You can check the "Errors" type only in the capture log filter). So, if the Low-Level I/O does not service a request quickly enough, it might or might not cause starvation, depending on what was already buffered by the Stream Manager. If it is too busy for a long period of time, the stream will starve, and you will see it in the capture log.