At any time, Windows Media Player can signal a break in the input stream by calling the IMediaObject::Discontinuity method. This occurs routinely at the start and end of a stream, and also prior to each seek operation or when streaming content is interrupted for any reason. The sample DSP plug-in that the Windows Media Player Plug-in wizard generates does not need to deal with discontinuities for the following reasons:
- PCM samples are atomic, meaning they can be processed without regard to the other samples in the stream. Some video formats contain data that depends on key frames and compressed samples.
- The sample code is written to always force the client to process all output before the plug-in will accept more input.
The default implementation of IMediaObject::Discontinuity simply returns S_OK.