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• How to join 3 movieclips with ffmpeg with an added overlay to the second one ?

  16 avril 2014, par Alex Khvorov

  I want to add an overlay image to the clip and then add two short clips at the start and end of it

• Slowing down audio of a video using FFMPEG

  8 mars 2015, par jhodzzz

  Good day. Before anything else, I would like to say that I am a newbie with regards to video filters on FFMPEG. So please bear with me, :) Thanks in advance..

  Anyways, I am trying to slow down a video clip that will be embedded and played within my delphi project. So far, slowing the video works fine by using the setpts filter. here’s my partial code :

  FFPlayer.VideoFilters := Format('setpts=(1/' + FloatToStr(FSpeed) + ')*PTS, nativeeq=%d:%d:%d:%d, nativehue=%d:%d:%d:%d',
  
    [0, 0, 0, 0, 0, 0, 0, 0]);

  where FSpeed is a changing value that ranges 0.5 - 2.5. With this code, the video capture speeds up or slows down, but the audio doesn’t. So as I was searching for the code to slow down the audio, I came across this link that provides the filter codes for speeding up or slowing down the video capture and audio. A line there mentioned that the filter code to slow down the audio and video capture at the same time is :

  ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mkv

  I tried adding "atempo=2.0" to my partial code making it :

  FFPlayer.VideoFilters := Format('setpts=(1/' + FloatToStr(FSpeed) + ')*PTS, atempo=2.0, nativeeq=%d:%d:%d:%d, nativehue=%d:%d:%d:%d',
  
    [0, 0, 0, 0, 0, 0, 0, 0]);

  but video didn’t show up at all.

  I am hoping you could enlighten me with this one. 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 ?