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• Extract alpha from video ffmpeg

  23 octobre 2018, par Yarik Denisyk

  I want to overlay transparent video on the background image. I have a video where the top half is RGB object and bottom half is an alpha mask.

  Now, for making this I do next steps :

  1) I am extracting all frames from video and save to the folder

  2) Each frame splitting to top and bottom half bitmap

  3) Top bitmap composite with bottom mask for extract alpha and get a frame with transparent background

  3) I am drawing each frame on the background and save to a folder

  4) Create a video using FFmpeg

  The problem is step 2, 3 and 4, they very slow. Maybe has another way to overlay transparent video on the background image ?

• Streaming jpegs to a video on my server

  2 décembre 2013, par Andrew Simpson

  I found a solution to my problem IF I was using a Linux/UNIX machine. It is FFServer from the tools from FFMPEG.

  I had been using FFMPEG on my client Winform Desktop C# to convert jpegs into an OGG video file for playback.

  I have now been tasked with uploading the jpegs to my server and rendering it as a video.

  Optimum, I would start an FFMPEG process on my client PC and supply its stdin with jpegs in byte array format. I have achieved this (I have looked around) but is there a way to redirect the stdoutput to my server that can be picked up by my code on the server and render in real-time to my web User ?

  I have looked on the ffmpeg web site but I am unsure how to 'fit' it in with my process.

  This is my code so far :

      public byte[] EncodeAndUploadImages(string _args1, string _fn)  
  
      {
  
          byte[] _data = null;
  
          try
  
          {
  
              clientBuild = new Process();
  
              clientBuild.StartInfo.WorkingDirectory = Environment.CurrentDirectory;
  
              clientBuild.StartInfo.Arguments = " -f mjpeg -r 30 -i - -c:v libtheora -q:v 7 -r 30 -f ogg -";
  
              clientBuild.StartInfo.FileName = Environment.CurrentDirectory + @"\ffmpeg.exe";
  
              clientBuild.StartInfo.UseShellExecute = false;
  
              clientBuild.StartInfo.RedirectStandardOutput = true;
  
              clientBuild.StartInfo.RedirectStandardError = true;
  
              clientBuild.StartInfo.RedirectStandardInput = true;
  
              clientBuild.StartInfo.CreateNoWindow = true;
  
              clientBuild.StartInfo.LoadUserProfile = false;
  
              clientBuild.EnableRaisingEvents = true;    
  
              clientBuild.Start();
  
  
  
              using (BinaryWriter bw = new BinaryWriter(clientBuild.StandardInput.BaseStream))
  
              {
  
                 //I am simulating a stream of jpegs coming in////////////////
  
                  for (int i = 1; i < 20; i++)
  
                  {
  
                      using (MemoryStream ms = new MemoryStream())
  
                      {
  
                          System.Diagnostics.Debug.Write(i.ToString("00000"));
  
                          Bitmap bmp = new Bitmap("h:\\streamin\\" + i.ToString("00000") + ".jpg");
  
                          bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
  
                          bw.Write(ms.ToArray());                           
  
                          bmp.Dispose();
  
                          ms.Close();
  
                      }
  
                  }
  
                  bw.Close();
  
              }
  
  
  
              // I need some in my ffmpeg arguments to do something here//////   
  
              mStandardOutput = clientBuild.StandardOutput.BaseStream;
  
              mStandardOutput.BeginRead(mReadBuffer, 0, mReadBuffer.Length, StandardOutputReadCallback, null);
  
              clientBuild.WaitForExit();
  
              _data = mStandardOutputMs.ToArray();
  
              mStandardOutput.Close();
  
          }
  
          catch (Exception _ex)
  
          {
  
  
  
          }
  
          finally
  
          {
  
              clientBuild.Dispose();
  
          }
  
          return _data;
  
      }

  Thanks

• VB.NET - frame capture issue and syncing audio with video using ffmpeg issue

  1er décembre 2013, par Sunny D'Souza

  I have a code in VB.NET that capture fullscreen images of the desktops at regular intervals (code runs in timer tick event of 20ms) Within the same ticker event I even capture the audio.
  Code to capture the screenshots

      Filenum.Text = Filenum.Text + 1
  
      Dim screensize As Size = New Size(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
  
      Dim BMP As New Bitmap(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
  
      Dim ga As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(BMP)
  
      ga.CopyFromScreen(New Point(0, 0), New Point(0, 0), screensize)
  
      Cursor.Draw(ga, New Rectangle(Cursor.Position, Cursor.Size))
  
      Dim fileDiro As String = My.Computer.FileSystem.CurrentDirectory + "\Recorder\VidShots-" + DT + "\img"
  
  
  
      Dim frame As String = Filenum.Text
  
      BMP.Save(fileDiro + frame + ".png")

  I notice the above code runs OK (not too much as expected) when doing regular recording of desktop but when recording a video or fast motion capture, it fails to generate enough frames to create a decent clip.

  '''' Code exclusively for Audio recording - Start audio recording - added 22/09/2013
  
  
  
   mciSendString("open new Type waveaudio Alias recsound", "", 0, 0)
  
      mciSendString("record recsound", "", 0, 0)
  
  
  
   '''' Code exclusively for Audio recording - Stop audio recording - added 22/09/2013
  
      Using w As New IO.FileStream( _
  
                      My.Computer.FileSystem.CurrentDirectory + "\Recorder\sound.mp3", _
  
                      IO.FileMode.Create _
  
                  )
  
          w.SetLength(64000)
  
      End Using
  
  
  
      Dim fP As String
  
      fP = My.Computer.FileSystem.CurrentDirectory & "\Recorder\sound.mp3"
  
      mciSendString("save recsound " & Chr(34) & fP & Chr(34), "", 0, 0)
  
      mciSendString("close recsound", "", 0, 0)
  
      My.Computer.Audio.Stop()

  The problem is when I try to mux together the audio and video using ffmpeg.exe, more often than not, the audio is out of sync with the video generated. Below are examples of the two ffmpeg statements that are executed.

   Dim startInfo As New ProcessStartInfo(My.Computer.FileSystem.CurrentDirectory & "\ffmpeg.exe")
  
         startInfo.Arguments = "-r " + max.ReadLine + " -analyzeduration 2147483647 -probesize 2147483647 -i Recorder/" + x + "/img%d.png -r 12 -b:v 900K Recorder/" + x + "/video.avi"
  
          Debug.Print(startInfo.Arguments.ToString)
  
  
  
          p = Process.Start(startInfo)
  
          p.WaitForExit()
  
          'Process.Start(My.Computer.FileSystem.CurrentDirectory & "\ffmpeg.exe", "-r 10 -analyzeduration 2147483647 -probesize 2147483647 -i Recorder/" + x + "/img%d.png -r 50 Recorder/" + x + "/video.avi"))
  
          Process.Start(My.Computer.FileSystem.CurrentDirectory & "\ffmpeg.exe", "-i Recorder/" + x + "/video.avi -i Recorder/sound.mp3 -map 0 -map 1 -codec copy -shortest Recorder/" + x + "/video1.avi")
  
          Debug.Print("-i Recorder/" + x + "/video.avi -i Recorder/sound.mp3 -map 0 -map 1 -codec copy -shortest Recorder/" + x + "/video1.avi")

  Could someone please help in getting the audio and video in sync ?