WebVTT line parameter not being parsed correctly to ASS/SSA

[felri]

Hello again, I found a problem related to the line:50% paramenter in VTT files and converting it to ASS/SSA files.

The fixable problem is that you are not setting the vmargin of the line in to_ass(), the way I'm fixing this is:

+let vmargin = i.position.map_or(0.0, |p| p.line as f32);
let mut line = SSAEvent {
    line_end: i.line_end,
    line_start: i.line_start,
    line_text: i.line_text.clone(),
+   vmargin,
    ..Default::default()
};

The unfixable problem is that VTT uses lines or percentage to define the the vertical position of the subtitle, ASS/SSA uses pixels, so if I send

line:50%or line:50

from VTT, ASS recognizes as 50 pixels, the only way I can fix this is to get the video height and change the values from percentage to pixels before sending it to the rsubs-lib, not related to your lib tho.