Public Overridable Sub PreviewIsEnabled( _
   ByVal _bsChannelID As String, _
   ByRef _pbEnabledAudio As Integer, _
   ByRef _pbEnabledVideo As Integer _
) 

public virtual void PreviewIsEnabled( 
   string _bsChannelID,
   out int _pbEnabledAudio,
   out int _pbEnabledVideo
)

public procedure PreviewIsEnabled( 
    _bsChannelID: String;
   Out  _pbEnabledAudio: Integer;
   Out  _pbEnabledVideo: Integer
); virtual; 

public: virtual void PreviewIsEnabled( 
   BSTR* _bsChannelID,
   [PARAMFLAG::Out] int _pbEnabledAudio,
   [PARAMFLAG::Out] int _pbEnabledVideo
) 

Parameters

_bsChannelID

channel ID. By default use empty string

_pbEnabledAudio

indicates whether audio preview is enabled

_pbEnabledVideo

indicates whether video preview is enabled

Here is example of how to check whether preview is enabled:

int isAudio;
int isVideo;
m_objPreview.PreviewIsEnabled("", out isAudio, out isVideo);

Reference

MFPreviewClass Class
MFPreviewClass Members