Implement on input or output pins of filters when you want precise control of the data stream. This interface enables you to turn off portions of the filter graph's streams at specific times without affecting the rest of the graph. Although this interface can be used throughout the graph, the input pins of multiplexer filters are the primary users.

If you are writing a filter that will implement IAMStreamControlon one of its pins, you should set the STREAM_DISCARDING state so that the pin discards media samples in a timely fashion, rather than as soon as they are received. This means that if your pin is discarding samples as soon as it determines they are outside the time that the pin is supposed to be on, it will discard samples as fast as possible and the whole file could potentially be pushed into your filter and discarded in mere moments. This causes problems if the pin tries to call IAMStreamControl::StartAtat a later point in time because the entire file will have already been discarded. To avoid pins from dumping media samples as fast possible, your code should check the media sample's timestamp and wait until the reference clock verifies that the end of the sample's time has actually occurred before discarding. This is known as discarding in a timely fashion (see CBaseStreamControlfor an implementation that does this).

Use this interface to turn on or off certain portions of the filter graph's streams while other portions continue to process data. For example, your application can tell a video filter's input pin precisely when to start or stop playback, independent of what is happening in the rest of the graph. This assists in frame accuracy when exact start or stop times are important.

The following table shows the methods that appear in the Vtable beneath the standard COM methods inherited from IUnknown.