Windows Media Video 9 Screen Decoder

Article
04/12/2010

The Windows Media Video 9 Screen decoder decodes streams that were encoded by the Windows Media Video 9 Screen Encoder.

Class Identifier

The class identifier (CLSID) for the Windows Media Video 9 Screen decoder is represented by the constant CLSID_CMSSCDecMediaObject. You can create an instance of the decoder by calling CoCreateInstance.

Input Types

The four-character code (FOURCC) for Windows Media Video Screen Version 9 encoded content is "MSS2".

The following input types are supported by the Version 9 Screen decoder.

MEDIASUBTYPE_MSS2

Output Types

The following output types are supported by the Version 9 Screen decoder when it is being used as a DirectX Media Object (DMO).

MEDIASUBTYPE_RGB24
MEDIASUBTYPE_RGB32
MEDIASUBTYPE_ARGB32
MEDIASUBTYPE_RGB565
MEDIASUBTYPE_RGB555
MEDIASUBTYPE_RGB8

The following output types are supported by the Version 9 Screen decoder when it is being used as a Media Foundation Transform (MFT).

MFVideoFormat_RGB24
MFVideoFormat_RGB32
MFVideoFormat_ARGB32
MFVideoFormat_RGB565
MFVideoFormat_RGB555
MFVideoFormat_RGB8

Remarks

A screen 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 screen 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 screen decoder behaves as a DMO or an MFT.

Operating system	Decoder behavior
Windows XP	A Windows Media Screen decoder always behaves as a DMO.
Windows Vista and Windows 7	By default, a Windows Media Screen decoder behaves as a DMO. If you obtain an IMFTransform interface on a screen decoder, it behaves as an MFT.

You can use the same CLSID (CLSID_CMSSCDecMediaObject) to create the Version 7 Screen decoder and the Version 9 Screen decoder. The FOURCC for Windows Media Video Screen Version 7 encoded content is "MSS1". The Version 7 Screen decoder supports the MEDIASUBTYPE_MSS1 input type.

Requirements

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