Quality-Control Management

The Microsoft® DirectShow® stream architecture provides for graceful adaptation of media rendering to overloaded or underloaded media streams. The IQualityControl interface is used to send quality-control notifications from a renderer filter either upstream, eventually to be acted on by some filter in the graph, or directly to a designated quality control manager. The base classes implement the passing of quality control notifications upstream by providing the IQualityControl interface on the output pins of filters. Quality control notification uses a Quality structure, which indicates whether the renderer is overloaded or underloaded. A filter capable of, say, discarding samples to relieve an overloaded condition, can then act on this notification. This is typically done by a source filter but could be done by other filters. For example, the DirectShow AVI Decoder filter skips samples until the next key frame when it receives a quality control notification.