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Let's see what Microsoft think, what DirectShow is:
"Microsoft� DirectShow� is an application programming interface (API) for client-side playback, transformation, and capture of a wide variety of data formats. DirectShow is the successor to Microsoft� Video for Windows� and Microsoft� ActiveMovie�, and it improves on these older technologies in significant ways. For developers, the component architecture of DirectShow makes it easy to support new and custom data formats or create custom effects and transforms on standard formats. DirectShow provides default support for MPEG-1 (including MP3), MPEG-2 parsing and multiplexing, MPEG-4, AVI, WAV, RIFF, and DVD." [copied from: http://www.microsoft.com/Developer/PRODINFO/directx/dxm/help/ds/default.htm]
Sorry for copying, but I couldn't say it better.
Mircosoft�, DirectShow� and Video for Windows� are registered trademarks and ActiveMovie� is trademark of Microsoft Corporation in the U.S. and/or other countries.
