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GetSampleBuffer Method

Summary

Gets a sample buffer from a stream.

Syntax

C++/CLI

public MediaSample GetSampleBuffer( 
   int Stream, 
   int TimeOut 
)

public: 
MediaSample^ GetSampleBuffer(  
   int Stream, 
   int TimeOut 
)

Parameters

Stream
The zero-based index that indicates the stream for which to get the sample buffer.

TimeOut
Maximum time to wait for a free sample buffer, in milliseconds. If TimeOut is -1, the method's time-out interval never elapses.

Return Value

A MediaSample object that represents the sample buffer.

Remarks

The buffer retrieved by this method comes from a pool of buffers. Make no assumptions on the number of available buffers. If you get a buffer, fill it with data and then deliver it downstream with DeliverSample. Release the buffer (by setting the reference to Nothing) before getting another. This is because there can only be one buffer available at a time. If the method fails, an error is raised. For more information, refer to the Error Codes. If the method does not retrieve a buffer within the allotted time it will return VFW_E_TIMEOUT [0x8004022E]. If this happens, the timeout specified may be too small and all of the available buffers are currently being sent downstream. If you get the sample in .NET, call System.Runtime.InteropServices.Marshal.ReleaseComObject to release the sample before getting another sample.

Example

using Leadtools; 
using Leadtools.Multimedia; 
using LeadtoolsMultimediaExamples.Fixtures; 
 
 
public bool _result = false; 
public ConvertCtrlForm _form = new ConvertCtrlForm(); 
public ConvertCtrl _convertctrl; 
 
// input files and output file 
string inFile1 = Path.Combine(LEAD_VARS.MediaDir, "ConvertCtrl_Source1.avi"); 
string inFile2 = Path.Combine(LEAD_VARS.MediaDir, "ConvertCtrl_Source2.avi"); 
string outFile = Path.Combine(LEAD_VARS.MediaDir, "ConvertCtrl_ConcatAVIFilesExample.avi"); 
 
public void ConcatAVIFilesExample() 
{ 
   ConvertCtrl pConvert1; 
   ConvertCtrl pConvert2; 
   MultiStreamSource pMSSource; 
   MultiStreamTarget pMSTarget; 
   Int64 lStart; 
 
   MediaType pmt; 
   MediaType pInsertedMediaType; 
 
   pConvert1 = new ConvertCtrl(true); 
   pConvert2 = new ConvertCtrl(true); 
 
   pMSSource = new MultiStreamSource(); 
   pMSTarget = new MultiStreamTarget(); 
 
   // set the start time to be 0 
   lStart = 0; 
 
   // set the input filename 
   pConvert1.SourceFile = inFile1; 
 
   // set the output sample to a target object 
   pMSTarget.StreamCount = 2; 
 
   // set the target media types for video and audio streams 
   pmt = new MediaType(); 
   pmt.Type = Constants.MEDIATYPE_Video; 
   pMSTarget.SetAcceptedMediaType(0, pmt); 
 
   pmt.Type = Constants.MEDIATYPE_Audio; 
   pMSTarget.SetAcceptedMediaType(1, pmt); 
 
   pmt = null; 
 
   // get the inserted media type for the first stream 
   pInsertedMediaType = pMSTarget.GetAcceptedMediaType(0); 
   pInsertedMediaType = null; 
 
   // set convert 1 target object 
   pConvert1.TargetObject = pMSTarget; 
 
   // start the source conversion, so we can get the media sample format 
   pConvert1.StartConvert(); 
 
   // initialize convert 2 
   // get the output media sample format and put it into the source object 
   pMSSource.StreamCount = 2; 
   pmt = pMSTarget.GetConnectedMediaType(0); 
   pMSSource.SetMediaType(0, pmt); 
   pmt = null; 
 
   pmt = pMSTarget.GetConnectedMediaType(1); 
   pMSSource.SetMediaType(1, pmt); 
   pmt = null; 
 
   // get the inserted media type for the first stream 
   pInsertedMediaType = pMSSource.GetMediaType(0); 
   pInsertedMediaType = null; 
 
   // set the output filename 
   pConvert2.TargetFile = outFile; 
 
   // set the source for convert 2 
   pConvert2.SourceObject = pMSSource; 
 
   // start the dest conversion 
   pConvert2.StartConvert(); 
 
   // convert first file 
   ConcateFile(pConvert1, pMSTarget, pMSSource, ref lStart); 
 
   /* 
   Restrict the output format to the media type of the source for the first file 
   That is because the two files must have the same media type for both video and audio 
   With video, you have to make sure the files have the same frame rate! Minor changes in 
   the frame rate might make the connection fail! 
   The control will tolerate differences in frame rate if you comment the next line 
   */ 
 
   pmt = pMSTarget.GetConnectedMediaType(0); 
   pMSTarget.SetAcceptedMediaType(0, pmt); 
   pmt = null; 
 
   pmt = pMSTarget.GetConnectedMediaType(1); 
   pMSTarget.SetAcceptedMediaType(1, pmt); 
   pmt = null; 
 
   // change the source file to second file 
   pConvert1.SourceFile = inFile2; 
 
   // start converting again 
   pConvert1.StartConvert(); 
 
   // convert second file 
   ConcateFile(pConvert1, pMSTarget, pMSSource, ref lStart); 
 
   // deliver end of sample to stop the conversion 
   pMSSource.DeliverEndOfStream(0, 1000); 
   pMSSource.DeliverEndOfStream(1, 1000); 
 
   if (pConvert2.State == ConvertState.Running) 
      pConvert2.StopConvert(); 
 
   // free the source and target objects 
   pConvert2.ResetSource(); 
   pConvert1.ResetTarget(); 
 
   pConvert1.Dispose(); 
   pConvert2.Dispose(); 
   pMSSource.Dispose(); 
   pMSTarget.Dispose(); 
 
   _result = File.Exists(outFile); 
} 
 
void ConcateFile(ConvertCtrl pConvert1, 
                 MultiStreamTarget pMSTarget, 
                 MultiStreamSource pMSSource, 
                 ref long lStart) 
{ 
   MediaSample pmsSrc = null; 
   MediaSample pmsDst = null; 
   long MediaTimeStart; 
   long MediaTimeStop; 
   long LastStart; 
   long LastStop; 
   int lSampleStream; 
   int lActualDataLength; 
 
   LastStop = 0; 
 
   do 
   { 
      // get the sample, allowing 10 s for the operation to complete 
      try 
      { 
         lSampleStream = pMSTarget.WaitForSample(1000); 
      } 
      catch (COMException cex) 
      { 
         if (cex.ErrorCode == (int)ErrorCode.VFW_E_TIMEOUT) 
         { 
            // end of the stream 
            break; 
         } 
         _result = false; 
         break; 
      } 
 
      try 
      { 
         // get the target sample 
         pmsSrc = pMSTarget.GetSample(lSampleStream, 0); 
         // get the source buffer 
         pmsDst = pMSSource.GetSampleBuffer(lSampleStream, 2000); 
      } 
      catch (Exception) 
      { 
         _result = false; 
         break; 
      } 
 
      // get the media time 
      pmsSrc.GetMediaTime(out MediaTimeStart, out MediaTimeStop); 
 
      // get the source sample time 
      pmsSrc.GetTime(out LastStart, out LastStop); 
 
      // set the destination sample time 
      pmsDst.SetTime(lStart + LastStart, lStart + LastStop); 
 
      // copy the data 
      lActualDataLength = pmsSrc.ActualDataLength; 
 
      // set the destination buffer  
      // we could Marshal the unmanaged buffer here, but no need since we are mearly  
      // setting the destination to the source buffer contents (unaltered data) 
      pmsDst.SetData(lActualDataLength, pmsSrc.GetData(lActualDataLength)); 
 
      // copy the other flags 
      pmsDst.Discontinuity = pmsSrc.Discontinuity; 
      pmsDst.Preroll = pmsSrc.Preroll; 
      pmsDst.SyncPoint = pmsSrc.SyncPoint; 
 
      // release the source sample 
      pmsSrc = null; 
 
      // deliver the destination sample 
      pMSSource.DeliverSample(lSampleStream, 1000, pmsDst); 
 
      // release the destination sample 
      pmsDst = null; 
   } 
   while (true); 
 
   pConvert1.StopConvert(); 
   lStart = LastStop; 
} 
 
static class LEAD_VARS 
{ 
   public const string MediaDir = @"C:\LEADTOOLS22\Media"; 
}

Requirements

Target Platforms

Reference

MultiStreamSource Class

MultiStreamSource Members

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Help Version 22.0.2022.12.7

Leadtools.Multimedia Assembly

Introduction

Getting Started

Namespaces

Leadtools.Multimedia Namespace

Leadtools.Multimedia.Common Namespace

Assemblies