Windows Media Video 9 Decoder

Článek
08/19/2021

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.

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.
g_wszWMVCNeedsDrain	Specifies whether the decoder should be drained. Windows 8 Read-only. 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.

Remarks

The maximum resolution allowed by the Windows Media Video 9 decoder is 4096x4096.

Requirements

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

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