I'd like to apply a dynamic drawbox before a drawtext, for example, with a fixed Y , X and H but with a dynamic W.

This is a trivial example:

/usr/bin/ffmpeg -y -loop 1 -t 5 -i img001.jpg -vf drawbox=x=0:y=0:w=t*300:h=100:[email protected] -y out.mp4

I expect to see a rectangle with the base width that increase with the time; it does not work, the box width is alwais fixed.

Is it possible to create a dynamic drawbox? if not, is there an alternative?

  • drawbox doesn't support time reference. What are you trying to do?
    – Gyan
    Feb 21, 2018 at 17:37
  • mmm I'd like to draw a rectangular shape, with some opacity, that comes from one side and fill the entire witdh of the video. Then the text appear over it, from one side for example. A kind of graphic introduction for the text.
    – GFCoder977
    Feb 22, 2018 at 14:03

1 Answer 1


Since drawbox doesn't support time reference, you need to use a workaround

ffmpeg -y -loop 1 -t 5 -i img001.jpg
  -filter_complex "[email protected]:s=Wx100[c];
  -y out.mp4

A color source is created equal to the final size of the box you wanted to draw i.e. image width (W) x 100. Then it is overlaid on the image and animated so that it starts revealing at the rate of 300*t.

  • It Works! I just did this modification to avoid the rectangle to "go away" from the screen heheh /usr/bin/ffmpeg -y -loop 1 -t 5 -i source/img001.jpg -filter_complex "[email protected]:s=1024x100[c];[0][c]overlay='if(lte(-1024+1500*t,0),-1024+1500*t,0)':0" -t 10 out.mp4
    – GFCoder977
    Feb 23, 2018 at 10:49

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