[FFmpeg-trac] #6947(undetermined:new): Unwanted visual formatting added when embedding subtitles

FFmpeg trac at avcodec.org
Fri Jan 5 14:59:39 EET 2018


#6947: Unwanted visual formatting added when embedding subtitles
-------------------------------------+-------------------------------------
             Reporter:  forthrin     |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 When playing an MP4 file with embedded subtitles in VLC, the subtitles are
 shown as specified by the user in VLC's subtitle preferences, but *not*
 "Font colour" and "Opacity".

 After discussing this with the VLC team, it may seem like FFmpeg secretly
 applies font colour and opacity when embedding the subtitles.

 {{{
 $ cat a.srt
 1
 00:00:00,000 --> 00:10:00,000
 The quick brown fox jumps
 over the lazy dog.

 $ ffmpeg -i a.mp4 -i a.srt -vcodec copy -scodec mov_text b.mp4
 }}}

 {{{
 $ ffmpeg -i b.mp4 b.srt

 $ cat b.srt
 1
 00:00:00,000 --> 00:09:56,459
 <font face="Serif" size="18">The quick brown fox jumps
 over the lazy dog.</font>
 }}}

 According to this, FFmpeg applies "Font face" and "Font size", but not
 "Font colour" and "Opacity". Strange...

 Anyway, unless the tx3g/mov_text format *requires* visual formatting, it
 seems most correct that a plain text subtitle is embedded *as-is*, eg.
 without any applied formatting, leaving all formatting to the video
 player.

 Please give insight how the subtitle embedding works, and how to embed
 subtitles without visual formatting.

 ffmpeg 3.4.1 (macOS/Homebrew)

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6947>
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