Summary

Summary

Source filters are absolutely essential because they generate the media samples that pass through the filter graph until rendered. Most hardware devices don t need custom DirectShow filters because DirectShow has wrappers to automagically make WDM and VFW device drivers appear as filters to DirectShow applications. Other source filters can read data from a file, from a URL, and so forth. Some source filters, such as the PushSource example explored in this chapter, create their own media streams. In large part, control of the filter graph is driven by the source filters it contains. In the implementation of PushSource, we ve explored how the different operating states of the filter graph are reflected in the design of a source filter. Therefore, a detailed study of source filters reveals how DirectShow executes a filter graph.