My final video output is 1080:1920 (9:16 aspect ratio), after padding.

In .ass file, I set PlayResX: 1080 PlayResY: 1920 and then the font-size=130. But, this font-size doesnt occupy exact 130 pixels on screen, when I render the video using ffmpeg.

If my video (in react js UI) width=108px; height=192px; then font-size = 13px (=130*(192/1920)) appear much larger than what 130px looks in 1080px:1920px (in proportion). However, if I multiple 13px by 2/3, I get almost the correct size.

What is a more robust method of setting font-sizes in .ass (with ffmpeg)?

  • Did you ever get the solution to this? i have been multiplying the font by 1.4 to make it almost the same but thats just an arbitrary number i found from trial and error.
    – prasum
    Jan 19 at 9:44


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