enable/disable the TV OUT on a graphic card?

Hi,

I have tried to enable and disable the TV OUT on a graphic
card by using the GDI function ChangeDisplaySettingsEx
function and the VIDEOPARAMETERS struct, but it does seem
to work.
According to Microsoft/MSDN it should be possible to
enable/disable TV OUT. They say:
To enable TV output, the caller (not the miniport driver)
should do the following:

·In dwFlags, set VP_FLAGS_TV_MODE and
VP_FLAGS_TV_STANDARD. Clear all other flags.

·Set dwMode to either VP_MODE_WIN_GRAPHICS or
VP_MODE_TV_PLAYBACK. Do not set both bits.

·Set dwTvStandard to the desired standard (for example
VP_TV_STANDARD_NTSC_M). Do not set any other bits in
dwTvStandard

The VIDEOPARAMETERS struct contains the above members.

I have tried the following (C++

VIDEOPARAMETERS vp = {0};

vp.Guid = GUID_VIDEOPARAMETERS;
vp.dwCommand = VP_COMMAND_SET;
vp.dwFlags = VP_FLAGS_TV_MODE | VP_FLAGS_TV_STANDARD
vp.dwMode = VP_MODE_TV_PLAYBACK;
vp.dwTVStandard = VP_TV_STANDARD_NTSC_M;

LONG lResult = ChangeDisplaySettingsEx
("\\\\.\\Display1",NULL,0,CDS_VIDEOPARAMETERS,&vp);

The function returns success (DISP_CHANGE_SUCCESSFUL), but
it does not enable the TV OUT.

Does anyone have any experience with this or any other
idea on how to enable/disable the TV OUT on a graphic card?