IMFTransform::GetInputAvailableType method (mftransform.h)

Article
10/13/2021

Gets an available media type for an input stream on this Media Foundation transform (MFT).

Syntax

HRESULT GetInputAvailableType(
  [in]  DWORD        dwInputStreamID,
  [in]  DWORD        dwTypeIndex,
  [out] IMFMediaType **ppType
);

Parameters

[in] dwInputStreamID

Input stream identifier. To get the list of stream identifiers, call IMFTransform::GetStreamIDs.

[in] dwTypeIndex

Index of the media type to retrieve. Media types are indexed from zero and returned in approximate order of preference.

[out] ppType

Receives a pointer to the IMFMediaType interface.

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code	Description
S_OK	The method succeeded.
E_NOTIMPL	The MFT does not have a list of available input types.
MF_E_INVALIDSTREAMNUMBER	Invalid stream identifier.
MF_E_NO_MORE_TYPES	The dwTypeIndex parameter is out of range.
MF_E_TRANSFORM_TYPE_NOT_SET	You must set the output types before setting the input types.

Remarks

The MFT defines a list of available media types for each input stream and orders them by preference. This method enumerates the available media types for an input stream. To enumerate the available types, increment dwTypeIndex until the method returns MF_E_NO_MORE_TYPES.

Setting the media type on one stream might change the available types for another stream, or change the preference order. However, an MFT is not required to update the list of available types dynamically. The only guaranteed way to test whether you can set a particular input type is to call IMFTransform::SetInputType.

In some cases, an MFT cannot return a list of input types until one or more output types are set. If so, the method returns MF_E_TRANSFORM_TYPE_NOT_SET.

An MFT is not required to implement this method. However, most MFTs should implement this method, unless the supported types are simple and can be discovered through the MFTGetInfo function.

If MFT_UNIQUE_METHOD_NAMES is defined before including mftransform.h, this method is renamed MFTGetInputAvailableType. See Creating Hybrid DMO/MFT Objects.

For encoders, after the output type is set, GetInputAvailableType must return a list of input types that are compatible with the current output type. This means that all types returned by GetInputAvailableType after the output type is set must be valid types for SetInputType.

Encoders should reject input types if the attributes of the input media type and output media type do not match, such as resolution setting with MF_MT_FRAME_SIZE, nominal range setting with MF_MT_VIDEO_NOMINAL_RANGE, or frame rate setting with MF_MT_FRAME_SIZE

Implementation Notes

If the MFT stores a media type internally, the MFT should return a clone of the media type, not a pointer to the original type. Otherwise, the caller might modify the type and alter the internal state of the MFT.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2008 [desktop apps \| UWP apps]
Target Platform	Windows
Header	mftransform.h
Library	Mfuuid.lib