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• Reuse value of a filter parameter for another one

  26 mars 2023, par Raphaël Goisque

  I have this command which draws a text ('First line Second line') on two different lines. Each text has a box drawn around it but they are not the same dimension as the size of the texts differs.

  


  As I want a unique box englobing the two lines, I thought of using the drawbox filter. The problem is that I need to know the values of the x parameter of the drawtext filters (i.e x=(main_w-text_w)/2) in order to set the x of the drawbox filter accordingly... but these value uses the variable text_w which is obviously not available from the drawbox filter.

  


  So does someone know if we can access the value of a parameter previously set ; or maybe create custom variables that we could reuse elsewhere in the command ?

  


  ffmpeg -y -i video.mp4 -vf /
"drawtext=box=1:boxcolor=white:fontcolor=black: /
text='First line':fontsize=55: /
x=(main_w-text_w)/2:y=main_h*1/6, /
drawtext=box=1:boxcolor=white:fontcolor=black: /
text='Second line':fontsize=55: /
x=(main_w-text_w)/2:y=main_h*1/6+57, /
drawbox=color=white" title.mp4


  


• create video with fluctuated background color and drawbox with fluctuated color ?

  27 mai 2019, par Wang

  Is there anyway to create a video with fluctuated background color choosing from a list for example [R, G, B] the background color along time will be R,G,B,R,G,B .... I might use nullsrc with geq. But seems the geq is quite slow which apply to each pixel.

  I would also like to change the color of drawbox too, is there any easy way to do it ? I knew we might be able to use openclsrc but it seems overkill for this simple task.

  Update, for drawbox I found a way, which is kind of abuse the timeline editing :

  ffmpeg -f lavfi -i smptebars=r=30:d=30:size=800x600 -vf "drawbox=enable='eq(mod(n,3),0)':x=0:y=0:t=20:c=red,drawbox=enable='eq(mod(n,3),1)':x=0:y=0:t=20:c=green,drawbox=enable='eq(mod(n,3),2)':x=0:y=0:t=20:c=blue" /tmp/test_box.mp4

• ffmpeg options that work with Chrome

  21 avril 2015, par James

  I am trying to find the magic options that make mp4 work in Chrome. I think my videos were working, but don’t seem to any more after Chrome updated.

  Chrome, Version 41.0.2272.101 (Windows)

  I tried some other machines and found some of the videos worked on older versions, and my Mac seems to still work on the latest Chrome.

  I am using the ffmpeg options to convert from png series,

  ffmpeg -framerate 10 -i dance%02d.png  -r 10 -pix_fmt yuv420p dance.mp4

  Some videos work, some don’t, some work some of the time, or stop half way through.

  I tried various other options like,

  ffmpeg -start_number 16 -framerate 10 -i dance%02d.png -r 10 -an -s hd720 \
  
  -vcodec libx264 -pix_fmt yuv420p -preset slow -profile:v baseline \
  
  -movflags faststart -y dance.mp4

  but this just seemed to make things worse.

  here is one of the videos,
  http://www.botlibre.com/media/a786625.mp4

  and another one,
  http://www.botlibre.com/media/a812450.mp4

  Firefox seems to work no problem, on any version, grey background though.
  IE works fine, white background.
  Safari works, grey background.

  Another thing, they videos used to have white background on older Chrome version, but now are grey, except on Mac still white.

  and one more thing. Webm format works, but anyone know the option to remove transparency ? I’m using,

  ffmpeg -i dance%02d.png  -r 10 -c:v libvpx -crf 10 -b:v 512k -c:a libvorbis dance.webm

  just want a solid white background.