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• ffmpeg alpha and transition leaving a ghosting effect

  18 octobre 2018, par Amin Baig

  I have the following ffmpeg command :

  //video from image and text insertion in one step
  
  ffmpeg -framerate 30 -loop 1 -t 5 -i 1.jpg -i 3D_Transition_02.mp4 -filter_complex "[0]format=rgba,scale=1280:720,split[img][a]; [1]format=rgb24,negate,scale=1280:720[tr];[a][tr]overlay=format=gbrp[al];[img][al]alphamerge,setsar=1,format=yuva444p,
  
  drawtext=enable='gte(t,.5)':box=1:boxcolor=black@.2:boxborderw=10:fontfile=fonts/Roboto-Black.ttf:fontcolor=white:fontsize=56:shadowcolor=Black:shadowx=1:shadowy=1
  
  :text='Some text here':y=h-th-10:x=10" -an -c:v libvpx -crf 10 -b:v 0 -quality realtime -auto-alt-ref 0 a1.mkv

  Using this command I create a v5 seconds video from a single image, there is a transition effect which is given to the image and then a text is rendered on it using drawtext.
  I create four videos using the above command only changing text and image, then I used the following command to conbine the four generated videos into one :

  ffmpeg -c:v libvpx -i a1.mkv -c:v libvpx -i a2.mkv -c:v libvpx -i a3.mkv -c:v libvpx -i 4.mkv -filter_complex "[1]setpts=PTS+5.00/TB[a2];[2]setpts=PTS+10.00/TB[a3];[3]setpts=PTS+15.00/TB[a4];[0][a2]overlay[o2];[o2][a3]overlay[o3];[o3][a4]overlay" out.mp4

  The problem I am facing is that there is a gost text from previous video which is seen on the next video (image attached for reference)

  I am totaly lost in how to rectify this issue. Please advise.

• ffmpeg add text every second with enable between filter

  12 janvier 2023, par HUNG

  ffmpeg -y -i public/media/vid1.mp4 -vf "drawtext=text='1':x=w-tw-50:y=50:fontcolor=black:fontsize=380:enable='between(t,1,2)',drawtext=text='2':x=w-tw-50:y=50:fontcolor=black:fontsize=380:enable='between(t,0,1)'" -codec:a copy public/media/vid1-1.mp4


  


  I want to add a number every second in a video. I googled and the syntax should like the above. However, only the text within between(t,0,1) can be shown and the value is keeping shown for the whole video duration. But I expected it should only show one second.

  


  I expected between(t,1,2) can show the text from 00:00:01-00:00:02. However, it never show.

  


• Why does the remainder of the video not appear in this FFMPEG complex filter graph ?

  10 janvier 2019, par Jonathan Gilbert

  I have a filter graph where I am trying to shift the first 18 seconds of a long video up by 60 pixels in each frame (the frame size is 1920x1040) without affecting the rest of the video. The graph definition looks like this :

  -filter_complex "[0:v] trim=start=0:duration=18 [pretitle];\
  
                   [0:v] trim=start=18,setpts=PTS-STARTPTS [remainder];\
  
                   color=color=black:size=1920x1040 [blank];\
  
                   [blank][pretitle] overlay=0:-60 [pretitle_shifted];\
  
                   [pretitle_shifted][remainder] concat [t];\
  
                   [t] ass=Subtitles.ass,fade=t=out:st=2608.6:d=2 [output]"
  
  -map [output] -map 0:1

  This filter graph runs without errors, but after the first 18 seconds, the video is just the subtitles on a black background. I can’t figure out why. :-(