DirectShow Merits

When deciding which codecs and filters to load, DirectShow uses the Merit system. The Merit system basically gives each codec or filter a rank and when a file is decoded, the codec with the highest merit who claims to be able to handle that media type will be used. This can sometimes cause problems in Multimedia applications because the specific decoder you would like your application to use may not necessarily be used if there is a another decoder on the machine which can handle the same media type with a higher merit.

There are many utilities available to change the filter merit, but when developing an application, you may want your installation to set the merit rather have the client run a utility. Attached is a command line utility which allows you to set the merit from your application or installation.

The usage is as follows:

SetMeritCommandLine [{class-id}] [merit]"

MERIT_Values:
MERIT_PREFERRED = 0x800000
MERIT_NORMAL = 0x600000
MERIT_UNLIKELY = 0x400000
MERIT_DO_NOT_USE = 0x200000
MERIT_SW_COMPRESSOR = 0x100000" << endl;
MERIT_HW_COMPRESSOR = 0x100050" << endl;

Errors:
-1 = Invalid number of arguements
-2 = Error obtaining class-id
-3 = Error setting merit

Example:

SetMeritCommandLine "{E2B7DF46-38C5-11D5-91F6-00104BDB8FF9}" "0x800000"

I have updated this utility to VS2008 (attached).

The new LEADTOOLS version 17 setup has a 'DirectShow Filters Merits' utility which shows the merit of the installed DirectShow filters and enables you to easily control the merit of each filter.

Also, you can now programmatically set the preferred decoders using our Multimedia toolkits.
For more information, please see the help topic " SetPreferredFilter Method" or contact support@leadtools.com