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Multimedia Transcoding Across Multiple Computers with LEADTOOLS

7 Jan 2013CPOL4 min read 35.3K   442   5  
The benefits of grid and distributed computing are well established and indisputable.  However, implementing them can be a nightmare – converting audio/video files in separate chunks can result in video hiccups and out of sync audio – but not with LEADTOOLS!

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The popularity of high definition televisions, computer monitors and online streaming has caused the average size of multimedia files to skyrocket, and with it, the time it takes to convert those files.  Files greater than a GB are not uncommon, and even codecs with optimizations for multiple CPU cores can take more than 20 minutes to convert those files from one format to another. 

One solution is to break up the file and convert each piece in parallel across multiple computers.  For example, a file over 1.5 GB which takes over 30 minutes to convert on a single 8 core machine can be reduced down to ~5 minutes when spread across networked computers.  The benefits of grid and distributed computing are well established and indisputable.  However, implementing them can be a nightmare – converting audio/video files in separate chunks can result in video hiccups and out of sync audio – but not with LEADTOOLS!

LEAD Technologies, Inc. has been a long time provider of programmer friendly DirectShow tools, processing filters and codecs.  The latest additions to LEAD’s Multimedia product line are the Elementary Stream DirectShow Filters and Cloud SDK.  Together, these technologies can create a powerful and robust solution for handling a large volume of multimedia transcoding jobs in less time and with more efficient use of computing resources.

Key Multimedia Features in LEADTOOLS SDKs

  • Play, capture and convert any DirectShow stream using high level .NET, COM and C++ programming interfaces
  • High performance audio and video codecs for H.264, H.263, MPEG-4, MPEG-2, MJPEG, MJPEG2000, AAC, AC3 and more
  • MPEG-2 Transport Stream with KLV
  • Over 100 DirectShow processing filters
  • Video Streaming and Conferencing
  • Live capture with DVR
  • Seamless integration with LEADTOOLS Cloud SDK for distributed computing applications
  • Windows Media Foundation SDK in development and coming soon!

SDK Products that Include Multimedia Technology

The Multimedia Conversion Code

The example attached to this article emulates a server farm where each individual virtual machine (FrmTranscoder) is given a piece of the audio/video file to convert. 

DirectShow Transcoding

LEADTOOLS Multimedia SDKs include a high level .NET interface that simplifies the development difficulties of DirectShow programming by automatically building graphs, connecting pins, setting encoder properties, etc.  To convert a file, one simply creates a Leadtools.Multimedia.ConvertCtrl, sets the conversion settings such as audio/video encoders and source/destination files, and LEADTOOLS does the rest.  Here’s a snippet from the FrmTranscoder_Load event in our example:

_transcodeData.TranscodeResult.Status = LTESHelper.Status.Working;
convertCtrl1 = new ConvertCtrl();
convertCtrl1.LoadSettingsFromFile(_transcodeData.SettingsFile, ConvertSettings.Compressors);
convertCtrl1.TargetFormat = TargetFormatType.LTES;
convertCtrl1.Complete += new EventHandler(convertCtrl1_Complete);
convertCtrl1.ErrorAbort += new ErrorAbortEventHandler(convertCtrl1_ErrorAbort);
convertCtrl1.Progress += new ProgressEventHandler(convertCtrl1_Progress);
convertCtrl1.SourceFile = _transcodeData.Sourcefile;
convertCtrl1.TargetFile = _transcodeData.DestFile;

Elementary Stream Filters

The LEAD Elementary Stream Source and Writer filters intelligently choose and synchronize the split/merge points.  They allow large files to be broken up, converted separately, and joined back together into a file that is indistinguishable from one converted by single process.

The conversion task is started by using a ConvertCtrl with the TargetFormat property set to TargetFormatType.LTES.  When you call StartConvert, the Elementary Stream Writer goes to work and splits the audio and video streams into separate files and also saves the catalog XML file which is used to keep track of where each clip or piece is located.  As you can see below, four clips were made from a single file (3 video & 1 audio):

<?xml version="1.0" encoding="utf-8" ?>
   <stream id="stream 1" type="{73646976-0000-0010-8000-00AA00389B71}" >
      <clip src="split-1-c1.ltes" start="0" duration="1349333333" />
      <clip src="split-1-c2.ltes" start="0" duration="1350000000" />
      <clip src="split-1-c3.ltes" start="0" duration="1337333334" />
   <stream id="stream 2" type="{73647561-0000-0010-8000-00AA00389B71}" >
      <clip src="split-2.ltes" start="0" duration="4037021315" />

Now that the source file is divided, each chunk can be divvyed up between the computers (in this example, FrmTranscoder).  After each virtual machine has finished, the Elementary Stream Reader is used to combine them back together for the final result.

int machineCounter = 1;
for (int streamIndex = 0; streamIndex < splitCatalogStreams.Length; streamIndex++)
   for (int clipIndex = 0; clipIndex < splitCatalogStreams[streamIndex].Clips.Length; clipIndex++)
      LTESHelper.TranscodeData transcodeData = new LTESHelper.TranscodeData();
      //Create the virtual machine and set its transcode data
      transcodeData.Sourcefile = Path.Combine(_txtTempFolder.Text, 
      string newFilename = splitCatalogStreams[streamIndex].Clips[clipIndex].SourcePath.Replace("split", "merge");
      transcodeData.DestFile = Path.Combine(_txtTempFolder.Text, newFilename);
      //Update the file path for the merge catlog
      mergeCatalogStreams[streamIndex].Clips[clipIndex].SourcePath = newFilename;
      transcodeData.SettingsFile = _conversionSettingsPath;
      transcodeData.MachineName = splitCatalogStreams[streamIndex].Type == 
          Constants.MEDIATYPE_Video ? String.Format("Transcoder {0} (Video)", 
          machineCounter) : String.Format("Transcoder {0} (Audio)", machineCounter);
      transcodeData.TargetFormat = LTMMFormatToLTESFormat(tempConverter.TargetFormat);
      FrmTranscoder transcoder = new FrmTranscoder();
      transcoder.TranscodeData = transcodeData;
      transcoder.PreviewVisible = _chkEnablePreview.Checked;
      transcoder.MdiParent = this.MdiParent;
      transcoder.FormClosed += new FormClosedEventHandler(transcoder_FormClosed);
      Log(String.Format("Sent {0} to {1}", transcodeData.Sourcefile, transcodeData.MachineName));

Image 1

Cloud Integration

Even on the same machine, the solution above can dramatically decrease the total conversion time since you can utilize more of the CPU.  If more processing power is needed, the Cloud SDK provides an easy to use framework to manage distributed tasks among any number of worker machines.

Though the attached example project is just an emulator, it can be easily ported to use the LEADTOOLS Cloud SDK where FrmMain and FrmSettings make up the central server and FrmTranscoder is refactored to a DLL that gets executed on each individual worker machine. 


LEADTOOLS provides developers with access to the world’s best performing and most stable imaging libraries in an easy-to-use, high-level programming interface enabling rapid development of business-critical applications.

Multimedia/DirectShow Transcoding is only one of the many technologies LEADTOOLS has to offer.  For more information on our other products, be sure to visit our home page, download a free fully functioning evaluation SDK, and take advantage of our free technical support during your evaluation.

Download the Full Multimedia Example

You can download a fully functional demo which includes the features discussed above.  To run this example you will need the following:


Need help getting this sample up and going?  Contact our support team for free technical support!  For pricing or licensing questions, you can contact our sales team ( or call us at 704-332-5532.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Help desk / Support LEAD Technologies, Inc.
United States United States
Since 1990, LEAD has established itself as the world's leading provider of software development toolkits for document, medical, multimedia, raster and vector imaging. LEAD's flagship product, LEADTOOLS, holds the top position in every major country throughout the world and boasts a healthy, diverse customer base and strong list of corporate partners including some of the largest and most influential organizations from around the globe. For more information, contact or
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