Summary

Summary

The DirectShow transform filter is a primary building block in all DirectShow applications. The structure of a transform filter is easy to understand and has a straightforward implementation. The implementation of a transform filter consists principally of a few methods to negotiate the media types acceptable to the filter, the calculation of buffer allocations for the output pin, and the specific transform function.

The YUVGray transform filter clearly demonstrates the media negotiation, allocation, and transform features of a transform filter, and it provides an easy-to-modify code base for your own transform filters. It s easy to extend YUVGray to support other video stream types, such as RGB, and with some extra code, the filter could convert between stream types on the fly. In Chapter 13, we ll cover DirectX Media Objects (DMOs), which can be used to provide a way to create audio and video transforms for any application, not just those that use DirectShow. Together, DirectShow transform filters and DMOs can be used to create a wide range of real-time media effects.