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• Problems building Image slideshow with sliding transition using ffmpeg

  23 juin 2016, par nanestev

  I’m trying to create image slideshow with slide transition using ffmpeg and the following command :

  ffmpeg -loop 1 -i img1.jpg -loop 1 -i img2.jpg -loop 1 -i img3.jpg ^
  
  -filter_complex ^
  
  "nullsrc=size=800x600[v0]; ^
  
  [0:v]trim=duration=5,scale=800x600,setpts=PTS-STARTPTS[v1]; ^
  
  [1:v]trim=duration=5,scale=800x600,setpts=PTS-STARTPTS[v2]; ^
  
  [2:v]trim=duration=5,scale=800x600,setpts=PTS-STARTPTS[v3]; ^
  
  [v0][v1]overlay=x='min(-w+(t*w/0.5)\,0)':shortest=1[vv0]; ^
  
  [v1][v2]overlay=x='min(-w+(t*w/0.5)\,0)':shortest=1[vv1]; ^
  
  [v2][v3]overlay=x='min(-w+(t*w/0.5)\,0)':shortest=1[vv2]; ^
  
  [vv0][vv1][vv2]concat=n=3:v=1:a=0 [video]" -map "[video]" output.mp4

  I want every image to slide in from left for 0.5 seconds and stay for further 4.5 seconds, before it’s being overlapped by the next one and so on.

  First problem is that it takes 2-3 minutes to build video with just 3 images and I want to add more images which will result in extremely long build time.

  Second problem is that video should be 15 seconds long, but it’s only 8 as first image is shown for 5 seconds, second is shown for 2 and the last one just for 1 second.

  Your help will be greatly appreciated.

• create multiple movie thumbnails using ffmpeg (one at a time) failing

  2 septembre 2013, par Christopher Johnson

  I'm using this small bit of code to create thumbnails of videos being uploaded to my site :

  public static void GetThumbnail(string video, string thumbnail)
  
  {
  
      var cmd = "ffmpeg  -itsoffset -1  -i " + '"' + video + '"' + " -vcodec mjpeg -vframes 1 -an -f rawvideo -s 320x240 " + '"' + thumbnail + '"';
  
      var startInfo = new ProcessStartInfo
  
      {
  
          WindowStyle = ProcessWindowStyle.Hidden,
  
          FileName = "cmd.exe",
  
          Arguments = "/C " + cmd
  
      };
  
  
  
      var process = new Process
  
      {
  
          StartInfo = startInfo
  
      };
  
  
  
      process.Start();
  
  }

  I'm uploading the videos one at a time asynchronously. The first video thumbnail gets created just fine, but each subsequent one does not get created. I've noticed that if I try to delete subsequent videos from the file system, it says it can not delete them because they are in use by ffmpeg. I can delete the first one that finished processing just fine. I have to kill the ffmpeg process from task manager for all of the others that it's holding open. Why is ffmpeg only working the first time through and then holding the video's open in an open process afterwards ?

  I also tried creating multiple thumbnails one at a time from the command prompt and that worked fine (the process does not stay open either).

  What am I missing in my c# code to make sure the process finishes, and then terminates ?

• Can't get the right formula to set frame pts for a stream using libav

  4 avril 2022, par user1365836

  I'm trying to save a stream of frames as mp4.
Source framerate is not fixed and it stay in the range [15,30]

  


  Encoder params :

  


  ...
eCodec.time_base = AVRational(1,3000);
eCodec.framerate = AVRational(30, 1);
...


  


  Stream params :

  


  eStream = avformat_new_stream(eFormat, null);                
eStream.codecpar = codecParams;
eStream.time_base = eCodec.time_base;


  


  Decoder time_base is 0/1 and it marks each frame with a pts like :

  


  480000
528000
576000
...


  


  PTS(f) is always == PTS(f-1)+48000

  


  Encoding (dFrame is the received frame, micro the elapsed time in microseconds) :

  


  av_frame_copy(eFrame, dFrame);
eFrame.pts = micro*3/1000;


  


  This make the video playing too fast.
I can't understand why, but changing micro*3/1000 to micro*3*4/1000 make the video play at the correct speed (checked against a clock after many minutes of varying fps)

  


  What am I missing ?