[FFmpeg-user] drawtext to a (transparent) bounding box

Jannes Faber jannes.faber at gmail.com
Mon Feb 23 17:55:25 CET 2015


Video editting newbie here.

I'm trying to use addtext onto a box and then overlay that box on a video.
That works fine, except when I try to make the bounding box  transparent.
The problem is that the text itself becomes transparent too, not just the
bounding box.

I asked this question here and included some screenshots and example code:


The very helpful comment I got so far:

"I think what's happening is that drawtext isn't writing the alpha channel,
so overlay just sees a rectangle with uniform alpha. The opacity controls
for drawtext just affect how it blends its text into the frames it draws
on." - Peter Cordes

It feels a bit like a bug in ffmpeg to me, but I'm sure there's a good
explanation. And I'm wondering if there's another/better way to do it?

Thank you.


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