| Microsoft DirectX 9.0 |
With Microsoft® DirectShow® you can create applications that play and write Advanced Systems Format (ASF) files, including ASF files containing Windows Media®-based content and files that are protected by Digital Rights Management (DRM). Advanced Systems Format (ASF) is the file container for Windows Media-based content and also for MPEG-4 content that is created with the Microsoft MPEG-4 Encoder DMO. In DirectShow, this Encoder (and the corresponding MPEG-4 decoder) can only be accessed through the WM ASF Reader and WM ASF Writer filters. These filters use the Windows Media Format SDK, which must be installed separately.
Important The WM ASF Reader and WM ASF Writer filters were first made available in DirectShow 8.0; they are wrapper filters for the Windows Media Format SDK. The filters that ship with DirectShow 8.1 and 9.0 support Version 7.0 and 7.1 of the Windows Media Format SDK. When the Windows Media Format 9 Series SDK is released, it will contain versions of these filters (along with the DMO Wrapper filter) that support Windows Media 9 Series. Documentation for these filters is in the Windows Media 9 Series SDK, not in the DirectShow SDK. These filters will supersede the filters in DirectX 9.0. Developers are highly encouraged to install the Windows Media 9 Series SDK and use the latest version of the WM ASF Reader, WM ASF Writer, and DMO Wrapper filters.
If you install the Windows Media Format 9 Series SDK after installing the DirectX 8.x or 9.x SDK, you will overwrite the DirectX version of qasf.dll with the Windows Media 9 Series version. This should not present any problems except possibly in one scenario where it will result in different behavior in the DirectShow IGraphBuilder::RenderFile method. The Windows Media Format 9 Series SDK version of the WM ASF Reader is the default source filter for the .asf, .wmv, and .wma file name extensions. This means that the WM ASF Reader is automatically created and added to the filter graph by the Filter Graph Manager in methods such as IGraphBuilder::RenderFile or IGraphBuilder::AddSourceFilter when a file of this type is specified. In DirectX 9.0 and earlier, and Windows XP Service Pack 1 and earlier, the RenderFile method will cause the older Windows Media Source Filter to be loaded for file playback. This behavior was maintained to ensure backward compatibility with applications that used the Windows Media Player 6.4.
For more information on the Windows Media suite of software development kits, see the Audio and Video section of the MDSN Library.
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