Windows Media Video 9 Decoder

Article
04/12/2010

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

Class Identifier

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.

Interfaces

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. For information about the IDMOQualityControl interface, see the DirectX Media Objects section of the DirectShow SDK documentation.

Input Formats

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.

Category	FOURCC
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

Output Formats

The Windows Media Video decoder supports the following output media subtypes when it is acting as a DMO.

MEDIASUBTYPE_NV12
MEDIASUBTYPE_YV12
MEDIASUBTYPE_YUY2
MEDIASUBTYPE_UYVY
MEDIASUBTYPE_YVYU
MEDIASUBTYPE_NV11
MEDIASUBTYPE_RGB32
MEDIASUBTYPE_RGB24
MEDIASUBTYPE_RGB565
MEDIASUBTYPE_RGB555
MEDIASUBTYPE_RGB8

The Windows Media Video decoder supports the following output media subtypes when it is acting as an MFT.

MFVideoFormat_NV12
MFVideoFormat_YV12
MFVideoFormat_YUY2
MFVideoFormat_UYVY
MFVideoFormat_YVYU
MFVideoFormat_NV11
MFVideoFormat_RGB32
MFVideoFormat_RGB24
MFVideoFormat_RGB565
MFVideoFormat_RGB555
MFVideoFormat_RGB8

Properties

The Windows Media Video decoder supports the following properties.

Property	Description
MFPKEY_DECODER_DEINTERLACING	Specifies whether the codec decodes interlaced video frames from the compressed stream as progressive frames. Windows XP and later. Simple Profile, Main Profile, Advanced Profile. Read/write.
MFPKEY_DXVA_ENABLED	Specifies whether the decoder will use DirectX video acceleration hardware, if available. Windows XP and later. Simple Profile, Main Profile, Advanced Profile. Write-only.
MFPKEY_AVDecVideoSWPowerLevel	Specifies the power level for the decoder. Windows 7. Simple Profile, Main Profile, Advanced Profile, Image. Read/write.
MFPKEY_FI_ENABLED	Specifies whether the decoder should use frame interpolation. Windows XP and later. Simple Profile, Main Profile, Advanced Profile, Image. Write-only.
MFPKEY_FI_SUPPORTED	Specifies whether the decoder supports frame interpolation. Windows XP and later. Simple Profile, Main Profile, Advanced Profile, Image Read-only.
MFPKEY_NUMTHREADSDEC	Specifies the number of threads that the decoder will use. Windows Vista and later. Simple Profile, Main Profile, Advanced Profile, Image. Read/write.
MFPKEY_POSTPROCESSMODE	Specifies the post processing mode for the decoder. Windows Vista and later. Simple Profile, Main Profile, Advanced Profile, Image. Write-only.

Requirements

Client	Windows XP, Windows Vista, or Windows 7
Header	Wmcodecdsp.h
DLL	Wmvdecod.dll

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