kExportInfo_SourceHasVideo always return 0?

Hi,

I'm using SDK 5.5 to make an exporter plugin.

But i've noticed that:

kExportInfo_SourceHasVideo and kExportInfo_SourceHasAudio selector (in GetExportSourceInfo suite) always return 0 no matter what kind of file exported.

Is that my fault or is there really something wrong with these selectors?

Thanks.