[FFmpeg-user] Weird results with drawtext

[Michael Koch]

Am 18.09.2021 um 18:07 schrieb Cecil Westerhof via ffmpeg-user:
> I have several of the following (simplified):
>      drawtext=
>         enable     = 'between(t, 105, 115)':
>         text       = 'speaker':
>         y          = main_h - (text_h * 4),
>      drawtext=
>         enable     = 'between(t, 105, 115)':
>         text       = 'subject':
>         y          = main_h - (text_h * 2.2),
>
> I have been carefully tweaking to get them on the correct place.
> But when I was satisfied and generated all eight places where I wanted
> to have them the placement of the speaker and subject text is on
> different heights. Sometimes one or the other is different, sometimes
> both and sometimes they are the same.
>
> Is this a bug, or am I doing something wrong?
>

The content of the variable "text_h" depends on which characters you are 
printing.

If you don't use "text_h", then the characters "a" and "q" are printed 
at the same height:
ffmpeg -f lavfi -i color=yellow -lavfi 
drawtext=text='a':x=20:y=50,drawtext=text='q':x=40:y=50 -frames 1 -y 
out1.png

But if you use "text_h", then they are printed at different heights:
ffmpeg -f lavfi -i color=yellow -lavfi 
drawtext=text='a':x=20:y=50-text_h,drawtext=text='q':x=40:y=50-text_h 
-frames 1 -y out2.png

Michael