|Microsoft DirectX 9.0|
DirectShow defines two related clock times: reference time and stream time.
When a media sample has a time stamp t, it means the sample should be rendered at stream time t. For this reason, stream time is also called presentation time.
When an application calls IMediaControl::Run to run the filter graph, the Filter Graph Manager calls IMediaFilter::Run on each filter. To compensate for the slight amount of time it takes for the filters to start running, the Filter Graph Manager specifies a start time slightly in the future.