#include "ltmf.h"

C Syntax

HRESULT IltmfConvert_SetPreferredMediaSourceHandler(pConvert, MediaSourceHandlerType, Val)

C++ Syntax

HRESULT SetPreferredMediaSourceHandler(MediaSourceHandlerType, Val)

IltmfConvert *pConvert;

pointer to an interface

long MediaSourceHandlerType

value for a media source handler type



Sets a preferred media source handler's GUID.




Pointer to an IltmfConvert interface.


Value that indicates the desired media source handler type. For a list of possible values, refer to ltmfConvert_PreferredMediaSourceHandler Constants.


String that has the following possible values:

  • GUID of the media source handler

  • ltmfMediaSourceHandler_LEADDefault (this will use the default LEAD media source handler)

  • ltmfMediaSourceHandler_DontCare (this is the same as setting the value to NULL)

  • NULL (don't use any preferred media source handler - revert to the default Windows Media Foundation media source handler)

For a list of possible values, refer to ltmfMediaSourceHandler Constants.



The function was successful.

<> S_OK

An error occurred. Refer to the Error Codes or the HRESULT error codes in the MediaFoundation documentation.


By default, the toolkit creates media sources according to the default Media Foundation mechanism, and thats by using a Source Resolver which is standard way to create media sources. However, sometimes 3rd party media sources get installed on some computers and assigns their media source handler to a specific media type and are used instead of the media sources you shipped with your application. And unexpected problems can occur if these media sources are not working properly. The SetPreferredMediaSourceHandler method allows you to control which media sources are used in your application. You can decide to use a certain media source handler or you can choose to use only the LEAD ones.

Val is a string for the GUID of the media source handler. This GUID uniquely identifies the media source handler. Every media format has a registered media source handler(s) who are responsible of creating a media source for this media type.

For example, the GUID for the LEAD MPEG2 Transport Media Source Handler is:


If the MediaSourceHandlerType argument is equal to ltmfConvert_PreferredMediaSourceHandler_Generic, then the possible values for Val are: ltmfMediaSourceHandler_LEADDefault or ltmfMediaSourceHandler_DontCare.

If ltmfMediaSourceHandler_LEADDefault is specified, then the LEAD default media source handlers will be set for ALL of the values listed in ltmfConvert_PreferredMediaSourceHandler.

If ltmfMediaSourceHandler_DontCare is specified, then the internal list of the preferred media source handlers will be cleared and the media source will be created using the Media Foundation's default mechanism (Source Resolver).

Use the ltmfMediaSourceHandler_XXX constants whenever possible. See ltmfMediaSourceHandler Constants for a list of predefined values.

Required DLLs and Libraries


For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.


Win32, x64

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© 1991-2021 LEAD Technologies, Inc. All Rights Reserved.