Decklink still source filter

This filter is based on the PushSource sample from the DirectShow SDK.  It provides a continuous stream of video from a single bitmap frame, loaded from a file.  The IFileSourceFilter interface is supported so the filter can load and stream the bitmap.  This method can be called repeatedly even while the filter is streaming to update or change the source image.  The transition happens seamlessly which avoids graph rebuilding and disturbance to the video stream.  The filter also supports IAMStreamControl interface so that the stream can be controlled.

As this filter provides a stream of bitmap images it is also possible to provide some customisation to generate specialized bitmaps.  By defining special filenames the still source filter can provide test patterns without the need for the data to reside on disk.  Having virtual files in this way makes this filter very flexible.  Currently only a checker bitmap pattern is generated by using the 'BMD_Checker' filename.  This is used by the DecklinkKey sample.

Blackmagic Design.