Public Overridable Sub StreamsAdd( _
   ByVal _bsStreamID As String, _
   ByVal _pExternOrRef As Object, _
   ByVal _bsPath As String, _
   ByVal _bsParam As String, _
   ByRef _ppItem As MItem, _
   ByVal _dblTimeForChange As Double _
) 

public virtual void StreamsAdd( 
   string _bsStreamID,
   object _pExternOrRef,
   string _bsPath,
   string _bsParam,
   out MItem _ppItem,
   double _dblTimeForChange
)

public procedure StreamsAdd( 
    _bsStreamID: String;
    _pExternOrRef: TObject;
    _bsPath: String;
    _bsParam: String;
   Out  _ppItem: MItem;
    _dblTimeForChange: Double
); virtual; 

public: virtual void StreamsAdd( 
   BSTR* _bsStreamID,
   IUnknown* _pExternOrRef,
   BSTR* _bsPath,
   BSTR* _bsParam,
   [PARAMFLAG::Out] MItem* _ppItem,
   double _dblTimeForChange
) 

Parameters

_bsStreamID

stream ID

_pExternOrRef

reference to external object (for example, live source)

_bsPath

path to source

_bsParam

additional parameters of element (“Live” to add live source, “Playlist” to add playlist). If you add file, you can set file properties here (like in FileNameSet), see MFile object: properties.

_ppItem

the new mixer stream

_dblTimeForChange

time interval for changes in seconds

Here is example of how to add a stream to the mixer:

'initialize a mixer
Dim m_objMixer As New MMixerClass()
m_objMixer.ObjectStart(Nothing)
m_objMixer.FilePlayStart()
'add stream to the mixer
Dim pItem As MItem
m_objMixer.StreamsAdd("", Nothing, "C:\myFile.wmv", "", pItem, 1.0)

//initialize a mixer
MMixerClass m_objMixer = new MMixerClass();
m_objMixer.ObjectStart(null);
m_objMixer.FilePlayStart();
//add stream to the mixer
MItem pItem;
m_objMixer.StreamsAdd("", null, @"C:\myFile.wmv", "", out pItem, 1.00);

var
myItem: MItem;
myMixer: MMixer;
myFile: IMfile;
myObject: IMObject;
myStreams: IMstreams;
begin
//initialize a mixer
myMixer:= CreateComObject(CLASS_MMixer) as MMixer;
myStreams:= myMixer as IMStreams;
myFile:= myMixer as IMFile;
myObject:= myMixer as IMobject;
myObject.ObjectStart(nil);
myFile.FilePlayStart();
//add stream to the mixer
myStreams.StreamsAdd('', nil, 'C:\myFile.wmv', '', myItem, 2.0);
end;

Reference

MComposerClass Class
MComposerClass Members