[FFmpeg-trac] #10356(undetermined:new): Incorrect escaping text from srt subtitles

[FFmpeg]

#10356: Incorrect escaping text from srt subtitles
--------------------------------------+----------------------------------
             Reporter:  Ashark        |                     Type:  defect
               Status:  new           |                 Priority:  normal
            Component:  undetermined  |                  Version:  6.0
             Keywords:                |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
--------------------------------------+----------------------------------
 Summary of the bug:
 I want to literally place "\n" string (not actually a line break) to the
 video. I created an srt file and hardsubbed it with subtitle video vilter:

 {{{
 $ ffmpeg -hide_banner -loglevel error -y -f lavfi -i
 color=size=1280x720:rate=10:color=black -vf
 "subtitles=subtitle_with_n.srt:force_style='Alignment=10,Fontsize=12'"
 -frames:v 1 output.png
 ffmpeg version n6.0 Copyright (c) 2000-2023 the FFmpeg developers
   built with gcc 12.2.1 (GCC) 20230201
 }}}

 But the escaping is done wrong. To hardsub the "\n" string, I escape
 backslash in srt: "\\n". But instead of escaping the backslash, it escapes
 the n, and the first '\' is written as is.

 I created this file subtitle_with_n.srt:
 {{{
 1
 00:00:00,000 --> 10:00:00,000
 line 1 \ \ \ backslash ampersand entity (also tried N
 letter entity) neither work in vlc nor in ffmpeg.
 line 2 \\n escapes n instead backslash. On vlc it makes backslash and
 breaks line. On ffmpeg it is backslash and space.
 line 3 \⁠n used wordjoiner (U+2060), works
 line 4 \​n zero width space, works in vlc, works in ffmpeg.
 line 5 \n breaks line in vlc, make space in ffmpeg. <b>Bold</b> tag works
 in both.
 line 6 \<i></i>n works for vlc, but in ffmpeg it is wrong.
 }}}

 This is self commenting. See screenshot for result.
 The expected non-crutch way is escaping work as normal: going from left to
 right of the string.

 Additional info:
 #9058 - bug about possibility to encode ampersand entities.
 #9808 - similar bug about escaping in another type of subtitles
 https://github.com/libass/libass/issues/194#issuecomment-351902555 -
 workaround by using word joiner symbol.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10356>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker