In Vegas 11 I was using settings in Options/Preferences/Interna:

Ignore Third party Codecs – False

Use Microsoft DV Codec – False

That would engage MainConcept DV Codec (installed on PC) that
has an access to change levels.

In Vegas 15 using same settings still some Vegas Internal
codec is used, not the MainConcept.

Is it due to MainConcept being 32-bit and Vegas 15 the
64-bit?

Any help is appreciated