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Transform filters transform the media data that comes into their input pins and send the transformed data out their output pins. Transform filters can be used to compress and decompress data, to split audio and visual data, or to apply effects, such as contrast or warbling, to media data. Microsoft DirectShow contains several sample transform filters that perform different kinds of transformations.
This article steps through the process of creating a transform filter. It covers five basic steps, and in the last step shows how to override the required member functions in your derived class to implement the transform filter. It answers two common questions that arise when creating transform filters: Which base class do I use? And how do I override member functions?
This article contains the following sections.