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Writing Subtitles

Introduction

LEADTOOLS toolkits support adding subtitles to certain multiplexer output streams.

Supported Demultiplexers

Currently, the LEAD MKV multiplexer is the only multiplexer supported.

Checking for Support

In order to determine if a multiplexer supports subtitles, call the ILMMuxSubtitle interface from the multiplexer in the convert graph. See the following code examples.

C++ Example

// find the convert multiplexer 
CComPtr<IUnknown> mux; 
m_convert->GetSubObject(ltmmConvert_Object_TargetFilter, &mux); 
if(mux) 
{ 
   // query IServiceProvider 
   CComQIPtr<IServiceProvider> sp = mux; 
   if(sp) 
   { 
      // check if the multiplexer subtitle service is available 
      sp->QueryService(__uuidof(LMMuxSubtitle), __uuidof(ILMMuxSubtitle), (void**) &m_subtitle); 
      if(m_subtitle) 
      { 
         // multiplexer supports subtitles 
      } 
   } 
}

C# Example

try 
{ 
   // find the convert multiplexer service provider 
   IServiceProvider sp = (IServiceProvider) convert.GetSubObject(ConvertObject.TargetFilter); 
   if (sp != null) 
   { 
      // check if the multiplexer subtitle service is available 
      subtitle = (LMSubtitleLib.LMMuxSubtitle)sp.GetService(typeof(LMSubtitleLib.LMMuxSubtitle)); 
      if (subtitle != null) 
      { 
         // multiplexer supports subtitles 
      } 
   } 
} 
catch 
{ 
 
}

VB.NET Example

Try 
   ' find the convert multiplexer service provider 
   Dim sp As IServiceProvider = DirectCast(convert.GetSubObject(ConvertObject.TargetFilter), IServiceProvider) 
   If sp IsNot Nothing Then 
      ' check if the multiplexer subtitle service is available 
      subtitle = DirectCast(sp.GetService(GetType(LMSubtitleLib.LMMuxSubtitle)), LMSubtitleLib.LMMuxSubtitle) 
      If subtitle IsNot Nothing Then 
         // multiplexer supports subtitles 
      End If 
   End If 
Catch 
End Try

Editing the Subtitle List

Use the following methods and properties to edit subtitles programmatically:

First, enter the edit mode by calling the ILMMuxSubtitle.EnterEdit method.
(Optional) To add a subtitle track from a subtitle file, call the ILMMuxSubtitle.AddTextTrackFromFile method. Currently, LEADTOOLS toolkits only support SubRip (*.srt) formatted files.
(Optional) To remove a previously added track, call the ILMMuxSubtitle.RemoveTrack method.
(Optional) Enumerate the added tracks using the ILMMuxSubtitle.TextTracks list.
Finally, leave the edit mode by calling the ILMMuxSubtitle.LeaveEdit method.

Using the Multiplexer Subtitle Property Page

In addition to programmatically editing the tracks directly in the application as described above, supported multiplexers have an additional property page for editing the subtitle track list. Any application that displays the multiplexer property pages can be used to edit the subtitle track list.

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