[FFmpeg-user] SSA/ASS subtitles supported colorspaces | incorrect colors

[N ONE]

Hello,

I'm trying to figure out if FFmpeg or the underlying subtitle rendering
library supports BT.709 color space for hardcoding subtitles. I've posted
the question with extensive details (with example files on Google Drive) on
superuser:

https://superuser.com/questions/1757284/ffmpeg-incorrect-colourspace-with-hardcoded-subtitles

According to this answer (https://superuser.com/a/1757297/867738), it is
deduced that FFmpeg uses BT.601 as standard for subtitles. This would
explain the issues when videos with subtitles tuned for BT.709 are rendered
with incorrect colors. The workaround to scale the color matrices works but
is really bad on performance.

Is this an issue related to FFmpeg which incorrectly determines the
colorspace used for rendering the subtitles? Or is this something that has
never been implemented?

Regards,

YTZ