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• C++/CLI FFmpeg av_read_frame returns a size but no data ?

  26 novembre 2013, par tommed

  I have written some C code to access ffmpeg and wrapped it in a C++/CLI (.NET managed) class. The program fetches a live video stream and extracts frames and converts them to PNG files.

  Unfortunately the images that are saved to disk are always black (opening them in Notepad++ shows that they are full of nulls).

  I am using the assemblies aformat/codec-55.dll and the development headers and libs for compilation from ffmpeg-20131120-git-e502783-win64-dev. The whole project is compiled using Managed C++ (Cpp/cli) .NET 4.0 for 64-bit.

  After some investigation the problem appears to be that av_read_frame fills the AVPacket->size value correctly, but the AVPAcket->data is always null. When the frame is finished (got==1) then the data for the AVFrame is just a matrix of nulls. :(

  Here is the code :
  Example code (sorry, but it didnt paste well into SO)

  I think the problem is at line 34 when the packet is returned like so :
  

  Please, how can I get this to work ? What have I done wrong ?

• how to get the argument of ffmpeg process in vb.net ?

  20 octobre 2015, par TOM

  i am writing a simple program to get the all the properties of a process like ffmpeg . i got most properties of predefined functions but i want to know the argument which i gave to the ffmpeg in vb.net ?

    For Each prog As Process In Process.GetProcesses
  
          If prog.ProcessName = "ffmpeg" Then
  
              al.Add(prog.Id)
  
          End If
  
      Next
  
  
  
   For Each id In al  
  
     Dim p As Process = Process.GetProcessById(id)
  
     listBox3.Items.Add(Process.GetProcessById(id).ProcessName)
  
     ListBox3.Items.Add(p.BasePriority)
  
     ListBox3.Items.Add(p.HandleCount)
  
     ListBox3.Items.Add(p.Id)
  
     ListBox3.Items.Add(p.MainWindowTitle)
  
     ListBox3.Items.Add(p.MaxWorkingSet)
  
     ListBox3.Items.Add(p.MinWorkingSet)
  
     ListBox3.Items.Add(p.PriorityBoostEnabled)
  
     ListBox3.Items.Add(p.PriorityClass)
  
     ListBox3.Items.Add(p.PrivilegedProcessorTime)
  
     ListBox3.Items.Add(p.ProcessName)
  
     ListBox3.Items.Add(p.ProcessorAffinity)
  
     ListBox3.Items.Add(p.StartTime)
  
     ListBox3.Items.Add(p.TotalProcessorTime)
  
    ListBox3.Items.Add(p.UserProcessorTime)
  
    lastBox3.Items.Add(p.WaitForInputIdle)
  
    ListBox3.Items.Add("========================")
  
  Next id

• Can't save process's output stream to file

  10 octobre 2018, par Wahid Masud

  I’m using ffmpeg.exe as a process and output the converted video to memory, then from memory I’m saving the data to a video file (this is the requirement I can’t directly save the converted video to a file). But the conversion is not working for some reason, Here is what I’ve tried,

  var ffmpeg = HttpContext.Current.Server.MapPath("~/FFMpeg/ffmpeg.exe");
  
  var outputDir = HttpContext.Current.Server.MapPath("~/Uploads/converted.mp4");
  
  var inputDir = "https://www.sample-videos.com/video/mp4/720/big_buck_bunny_720p_10mb.mp4";
  
  var args = "-i " + inputDir + " -c:v libx264 -preset veryslow -crf 26 " +
  
              "-ar 44100 -ac 2 -c:a aac -strict -2 -b:a 128k -";
  
  
  
  var process = new Process();
  
  process.StartInfo.UseShellExecute = false;
  
  process.StartInfo.FileName = ffmpeg;
  
  process.StartInfo.WorkingDirectory = ffmpeg.Replace("\\ffmpeg.exe", "");
  
  process.StartInfo.Arguments = args;
  
  process.StartInfo.RedirectStandardOutput = true;
  
  process.Start();
  
  process.EnableRaisingEvents = true;
  
  //process.WaitForExit();
  
  Stream output = process.StandardOutput.BaseStream;
  
  process.Exited += (sender, e) =>
  
  {
  
      using (var fileStream = File.Create(outputDir))
  
      {
  
          output.Seek(0, SeekOrigin.Begin);
  
          output.CopyTo(fileStream);
  
      }
  
  };  

  The output file converted.mp4 is created but its 0 kb.