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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 ?

• Revision 0dacecaf20 : Removing VP9DecoderConfig. We only used two members from that struct : max_threa

  9 mai 2014, par Dmitry Kovalev

  Changed Paths :
   Modify /vp9/decoder/vp9_decodeframe.c

  
   Modify /vp9/decoder/vp9_decoder.c

  
   Modify /vp9/decoder/vp9_decoder.h

  
   Modify /vp9/decoder/vp9_dthread.c

  
   Modify /vp9/vp9_dx_iface.c

  
  
  Removing VP9DecoderConfig.

  We only used two members from that struct : max_threads and inv_tile_order.
  Moving them directly to VP9Decoder struct.

  Change-Id : If696a4e5b5b41868a55f3cc971e1d7c1dd9d5f69

• FFMPEG syntax clarification question for the "between" function [closed]

  31 octobre 2024, par user2571504

  I've been using a crop filter script to hold the crop in one place for the first 750 frames, then automate a moving crop to follow some action in the clip. It's working great for chunky moves (5 pixel jumps as shown below) :

  


  -filter_script:v:0 crop-filter-script.txt

crop='1500:1000:100:
if(between(n,0,750),100,
if(between(n,751,756),105,
if(between(n,757,762),110,
if(between(n,763,768),115,
if(between(n,769,774),120,
if(between(n,775,780),125,
if(between(n,781,786),130,etc


  


  My question is about how "between" is interpreted. Does "between(n,751,756)" mean "frames 751, 752, 753, 754, 755 & 756" ? or does it exclude the start and ending frames, so that it's "between" those two numbers ? Like : 752, 753, 754 & 755 only ?

  


  Thanks !