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• Dynamic subtitles by ffmpeg

  8 septembre 2019, par Saeron Meng

  I would like to add some commentary texts into my video but I do not know how to use ffmpeg to realize this. The comments are like screen bullets through the screen, appearing in the right margin, moving and scrolling, and disappearing from the left.

  My thought is to count the length of the comments and define speeds for them to move and I have already gotten the comments saved as an xml file. But even though I can transfer it into srt file, the tricky problem is, it is hard to write the speeds of the subtitles, or something like that, in an srt file, and apply them to ffmpeg commands or APIs. Here is an example of comments (xml file) :

  <chat timestamp="671.195">
  
      <ems utctime="1562584080" sender="Bill">
  
          <richtext></richtext>
  
      </ems>
  
  </chat>
  
  <chat timestamp="677.798">
  
      <ems utctime="1562584086" sender="Jack">
  
          <richtext></richtext>
  
      </ems>
  
  </chat>

  The final result is like this (I did not find an example in websites in English. In China, such moving subtitles are called "danmu" or "screen bullets"), these colorful characters can move horizontally from right to left :

  

  1. I have searched some solutions on the Internet, most of which talk about how to write ass/srt files and add motionless subtitles. Like this :

  ffmpeg -i infile.mp4 -i infile.srt -c copy -c:s mov_text outfile.mp4

  3
  
  00:00:39,770 --> 00:00:41,880
  
  When I was lying there in the VA hospital ...
  
  
  
  4
  
  00:00:42,550 --> 00:00:44,690
  
  ... with a big hole blown through the middle of my life,
  
  
  
  5
  
  00:00:45,590 --> 00:00:48,120
  
  ... I started having these dreams of flying.

  But I need another kind of "subtitles" which can move.

  2. When it comes to scrolling subtitles, there are still some solutions : Scrolling from RIGHT to LEFT in ffmpeg / drawtext

  So my question is, how to combine the solutions above to arrange subtitles from top to bottom and let them move concerning the timestamps of the comments ?

• Transition effects between images using ImageMagick and FFMPEG [closed]

  7 mai 2013, par user1599914

  I'm trying to generate a video using still images. I'm using Image Magick's convert command to duplicate the images.

  convert screen6.png -duplicate 10 -background black -gravity center -extent 1024x576 4%06d.screen.transition.png

  I then use ffmpeg to encode the images.

  Problem 1 : How can I achieve good transition effects between the images ; effects such as circle in, box out, wheel, as well as kenburns effect.

  Problem 2 : How can I overlay the images with text, and make that text to animate or appear with some effects such as fade in, zoom out.

  Your help will be greatly appreciated.

• How to use values from array for scaling an image in FFMPEG expression ?

  27 juillet 2022, par Babagota

  I have an array containing 10 values, and I'm making a 5 seconds video at 2 frames per seconds.

  


  myArray = [110.2, 110.5, 113.5, 112.4, 112.4, 114.5, 110.3, 111.1, 115.3, 117.2]
#each value correspond to a scale, default is 100 so 110.2 is equal to a 10.2% zoom in


  


  How can I use those values to scale an image frame by frame ?

  


  ffmpeg -r 2 -loop 1 -i background.jpg -filter_complex "[0]scale=1:1[something here]" -t 5 out.mp4


  


  I've seen this question which is the same but for equalizers, but I can't reproduce the same thing for scaling. If I want to chain scales like this, I got an Invalid Expression.

  


  Thanks