[FFmpeg-user] dvdsub scaling 'fatness' work around?

[Mark Filipak]

On 25/07/2025 15.45, Devin Heitmueller wrote:
> On Fri, Jul 25, 2025 at 1:22 PM Mark Filipak <markfilipak.imdb at gmail.com> wrote:
>> No, SAR is 32/27, so DAR is 16/9. FFmpeg should scale just the same as a
>> player does [note], and then pad to 1920x1080. FFmpeg appears to
>> mis-scale the RLE subtitles (i.e. dvdsub), or, at least, to get the new
>> run lengths wrong -- a guess because I have no way to actually see the
>> run length numbers. (You know, now that I'm thinking about it more, I
>> don't know whether the problem is with FFmpeg's scaling or with the
>> players.)
> 
> ...it's entirely possible
> that it's just the player that doesn't know how to render them over
> 16:9 video.

I don't think that's the case -- at least, what you say doesn't seem
plausible. I ask: How would the player (MPV, VLC, PowerDVD) know that a
run length of 25 on line 460 does not apply to 1920x1080? I mean, why
would the player scale the subtitles... how would it know to scale the
subtitles, eh?

The answer would be to make JPGs of the subtitles and see. I wish I knew
how to do that.

--Mark.