Windows Media Video 9 Decoder
The Windows Media Video 9 decoder decodes video streams that were encoded by the Windows Media Video Encoder. The encoder and decoder support the following four categories of encoded video.
- Windows Media Video 9 Simple Profile
- Windows Media Video 9 Main Profile
- Windows Media Video 9 Advanced Profile
- Windows Media Video 9.1 Image
The class identifier (CLSID) for the Windows Media Video decoder is represented by the constant CLSID_CWMVDecMediaObject. You can create an instance of the video decoder by calling CoCreateInstance.
A video decoder object exposes the IMediaObject interface so that the object can be used as a DirectX Media Object (DMO), and it exposes the IMFTransform interface so that the object can be used as a Media Foundation Transform (MFT).
A video decoder behaves as a DMO or an MFT depending on which interfaces you obtain and which version of Windows is running. The following table shows the conditions under which a video decoder behaves as a DMO or an MFT.
|Operating system||Decoder behavior|
|Windows XP||A Windows Media video decoder always behaves as a DMO.|
|Windows Vista and Windows 7||By default, a Windows Media video decoder behaves as a DMO. If you obtain an IMFTransform interface on a video decoder, it behaves as an MFT.|
Beginning with Windows 7, the Windows Media Video decoder implements the IDMOQualityControl interface.
The following table shows the four-character codes (FOURCCs) that correspond to the categories of encoded input that are supported by the Windows Media Video decoder.
|Windows Media Video 9 Simple Profile||"WMV3"|
|Windows Media Video 9 Main Profile||"WMV3"|
|Windows Media Video 9 Advanced Profile||"WVC1"|
|Windows Media Video 9.1 Image||"WMVP" for 9.1, "WVP2" for 9.1 version 2|
The Windows Media Video decoder supports the following output media subtypes when it is acting as a DMO.
The Windows Media Video decoder supports the following output media subtypes when it is acting as an MFT.
The Windows Media Video decoder supports the following properties.
Specifies whether the codec decodes interlaced video frames from the compressed stream as progressive frames.
Specifies whether the decoder will use DirectX video acceleration hardware, if available.
Specifies the power level for the decoder.
Specifies whether the decoder should use frame interpolation.
Specifies whether the decoder supports frame interpolation.
Specifies the number of threads that the decoder will use.
Specifies the post processing mode for the decoder.
Specifies whether the decoder should be drained.
This property is used by the Windows Media Format runtime. The property type is VARIANT_BOOL. If the value is VARIANT_TRUE, the decoder should be drained after a discontinuity. For more information about draining an MFT, see Basic MFT Processing Model.
Note To query this property, use the IPropertyBag interface.
The maximum resolution allowed by the Windows Media Video 9 decoder is 4096x4096.
|Windows XP, Windows Vista, or Windows 7|