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object.SetPreferredFilter(FilterType As Long, Val As String) |
Remarks
Sets a preferred filter (decoder or demultiplxer)..
Value that indicates the filter type. For a list of possible values, refer to ltmmPlay_PreferredFilter Constants.
String that has the following possible values:
Display Name of the filter
Friendly Name of the filter
ltmmFilter_LEADDefault (this will use the default LEAD filter)
ltmmFilter_DontCare (this is the same as setting the value to NULL)
NULL (do not use any preferred filter - revert to the default DirectShow filter)
For a list of possible predefined values, refer to ltmmFilter Constants.
Remarks
By default, the toolkit uses filters according to the default DirectShow mechanism, which assigns a merit to each filter. The filters with the highest merits are tried first. If they fail, the filters with a lower merit are tried next until a combination of filters is found that can handle the graph. However, sometimes 3rd party filters get installed on some computers with a high merit and are used instead of the filters you shipped with your application. And unexpected problems can occur if these filters are not working properly. The SetPreferredFilter method allows you to control which filters are used in your application. You can decide to use a specific decoder or demultiplexer, or you can choose to use only the LEAD filters.
Val is a string for the Display Name or Friendly Name of the filter. It is best to use "Display Name" since display names are unique and no two filters can have the same Display Name. Two different filters can have the same Friendly Name. When two filters have the same name this function works on the first filter it internally enumerates that has the specified friendly name.
DirectShow filters have a friendly name and a display name. The friendly name is easy to remember and is usually displayed by GraphEdit or other filter enumeration utilities. But there can be more than one filter with the same friendly name, so it is safer to use the display name, since no two filters have the same display name.
Display names for software filters have the following format: @device:sw:GUID\GUID.
For example, Microsoft’s “MPEG-2 Splitter” has:
friendly name: MPEG-2 Splitter
display name: @device:sw:{083863F1-70DE-11D0-BD40-00A0C911CE86}\{3AE86B20-7BE8-11D1-ABE6-00A0C905F375}.
The display name for a particular filter can be obtained from the "DirectShow Filter List Utility" shipped with the toolkit. See Examples Programs and Demos for Win32/x64 for more details.
If the FilterType argument is equal to ltmmPlay_PreferredFilter_Generic, then the possible values for the Val argument are: ltmmFilter_LEADDefault or ltmmFilter_DontCare.
If ltmmFilter_LEADDefault is specified, then LEAD default decoders and demultiplexers will be set for ALL values listed in ltmmPlay_PreferredFilter.
If ltmmFilter_DontCare is specified, then the internal list of the preferred filters will be cleared and the DirectShow filter merit determines which filters will be used.
It is best to use the ltmmFilter_XXX constants whenever possible. See the ltmmFilter Constants for a list of these predefined values.
Win32, x64
See Also
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