WM_MEDIA_TYPE structure (wmsdkidl.h)
[The feature associated with this page, Windows Media Format 11 SDK, is a legacy feature. It has been superseded by Source Reader and Sink Writer. Source Reader and Sink Writer have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader and Sink Writer instead of Windows Media Format 11 SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]
The WM_MEDIA_TYPE structure is the primary structure used to describe media formats for the objects of the Windows Media Format SDK. For more information about media formats and what they are used for, see Formats.
Syntax
typedef struct _WMMediaType {
GUID majortype;
GUID subtype;
BOOL bFixedSizeSamples;
BOOL bTemporalCompression;
ULONG lSampleSize;
GUID formattype;
IUnknown *pUnk;
ULONG cbFormat;
BYTE *pbFormat;
} WM_MEDIA_TYPE;
Members
majortype
Major type of the media sample. For example, WMMEDIATYPE_Video specifies a video stream. For a list of possible major media types, see Media Types.
subtype
Subtype of the media sample. The subtype defines a specific format (usually an encoding scheme) within a major media type. For example, WMMEDIASUBTYPE_WMV3 specifies a video stream encoded with the Windows Media Video 9 codec. Subtypes can be uncompressed or compressed. For lists of possible media subtypes, see Uncompressed Media Subtypes and Compressed Media Subtypes.
bFixedSizeSamples
Set to true if the samples are of a fixed size. Compressed audio samples are of a fixed size while video samples are not.
bTemporalCompression
Set to true if the samples are temporally compressed. Temporal compression is compression where some samples describe the changes in content from the previous sample, instead of describing the sample in its entirety. Only compressed video can be temporally compressed. By definition, no media type can use both fixed sized samples and temporal compression.
lSampleSize
Long integer containing the size of the sample, in bytes. This member is used only if bFixedSizeSamples is true.
formattype
GUID of the format type. The format type specifies the additional structure used to identify the media format. This structure is pointed to by pbFormat.
pUnk
Not used. Should be NULL.
cbFormat
Size, in bytes, of the structure pointed to by pbFormat.
pbFormat
Pointer to the format structure of the media type. The structure referenced is determined by the format type GUID. Format types include:
| Media Type | Structure |
|---|---|
| WMFORMAT_VideoInfo | WMVIDEOINFOHEADER |
| WMFORMAT_WaveFormatEx | WAVEFORMATEX |
| WMFORMAT_MPEG2Video | WMMPEG2VIDEOINFO |
| WMFORMAT_WebStream | WMT_WEBSTREAM_FORMAT |
| WMFORMAT_Script | WMSCRIPTFORMAT |
Remarks
This is the same as the DirectShow structure AM_MEDIA_TYPE but is redefined in this SDK to avoid conflict with DirectShow names.
Requirements
| Minimum supported client | Windows 2000 Professional [desktop apps only],Windows Media Format 7 SDK, or later versions of the SDK |
| Minimum supported server | Windows 2000 Server [desktop apps only] |
| Header | wmsdkidl.h (include Wmsdk.h) |