Sub WriterOptionGet( _
   ByVal _eType As eMFWriterOption, _
   ByRef _pbsName As String, _
   ByRef _ppProps As IMFProps _
) 

void WriterOptionGet( 
   eMFWriterOption _eType,
   out string _pbsName,
   out IMFProps _ppProps
)

procedure WriterOptionGet( 
    _eType: eMFWriterOption;
   Out  _pbsName: String;
   Out  _ppProps: IMFProps
); 

void WriterOptionGet( 
   eMFWriterOption _eType,
   [PARAMFLAG::Out] BSTR* _pbsName,
   [PARAMFLAG::Out] IMFProps* _ppProps
) 

Parameters

_eType

type of option (format, video or audio codec)

_pbsName

option's name

_ppProps

properties of the option (internal attributes)

Here is example of how get currently specified video codec:

string codecName;
IMFProps videoProps;
m_objWriter.WriterOptionGet(eMFWriterOption.eMFWO_VideoCodec, out codecName, out videoProps);

Reference

IMFWriter Interface
IMFWriter Members