The DirectShow SDK and the Windows Media Format SDK

DirectShow and the Windows Media Format SDK offer complementary solutions for writing applications that create and play back Windows Media Format streams. For more information, read the white paper at http://www.microsoft.com/hwdev/vidcap/WM_DS.htm.

The ASF Writer filter accepts any number of input streams and creates an ASF file. The filter uses the Windows Media Format SDK to convert uncompressed audio or video files to Windows Media Format for storage in an ASF file, as the Windows Media Format specification requires.

You can use the ASF Writer in various scenarios including digital video (DV) capture, audio recompression, and conversion of Audio-Video Interleaved (AVI) or MPEG multimedia files for network streaming. This filter provides the only way to create Microsoft® Windows Media™ Audio (WMA) and Windows Media Video (WMV) files in DirectShow®. The filter can also create Windows Media Format files that are secured by Digital Rights Management (DRM).

The ASF Writer filter can be used only in conjunction with the Windows Media Format SDK. To develop applications that use this filter, you must have the Windows Media Format SDK installed on your development machine. When you download the SDK, Microsoft will send you a stub library by e-mail. This library contains a certificate that is required to access the Windows Media Format SDK. Without this library, an application cannot add the ASF Writer to a filter graph. To read or write DRM-enabled files, you need to obtain a different library from Microsoft, as described on the Windows Media Technologies Web site.