This chapter gives a short introduction on handling and processing subtitles with transcode and related programs.
DVD subtitle overlay mode
transcode provides a filter plugin for elementary DVD subtitle rendering in connection with -x vob. Use it with

transcode [...] -J extsub=<options>

The option string looks as follows (all options default to 0):


  • s   subtitle track id (0-31)
    Use tcprobe -H N with N>1 to find out if subtitle any packs are available in the program stream.

  • h   offset of subtitle with respect to bottom of frame in rows.
    Subtitles are placed at the bottom of the frame. Try this option to shift them up or down.

  • t   global display start time correction in msec.
    If you feel, subtitles are displayed not timely, adjust it with this option. This will affect all subtitles.

  • f   fast rendering, i.e., no anti-aliasing (0=off,1=on).
    Anti-aliasing of the font is performed by default. Switch it of (1) if your font is tiny and messed up by this feature.

  • w   render on post-processing (0=off, 1=on).
    Setting this option to 1 will render the subtitle on post-processing instead of pre-processing. This may improve subtitle quality but makes no sense after extensive resizing of the frame.

  • a   graylevel value a (0-255).
  • b   graylevel value b (0-255).
    Make another subtitle color visible with full intensity equal to 255. May lead to fatter fonts.

  • p   assign subtitle color p [0-3] to graylevel value a.
  • q   assign subtitle color q [0-3] to graylevel value b.
    Shuffle the color assignment by choosing another subtitle color between 0 and 3. Useful for black fonts on white background.

Example (1) changing color assignment:

  • -J extsub
    this one looks not as expected without any further options.

  • -J extsub=0:0:0:0:0:0:0:1:2
    shuffle the font color assignment using 1:2 looks like this, but has an ugly 3D effect.

  • -J extsub=0:0:0:0:0:0:0:1:3
    shuffle the color assignment using 1:3 looks better, but shows white shadows that make the font fatter but blurry

  • -J extsub=0:0:0:0:0:0:0:2:3
    shuffle the color assignment using 2:3 seems to be perfect. Nice and smooth looking letters.

  • -J extsub=0:0:0:1:0:0:0:2:3
    for comparison, we switch off anti-aliasing, see the difference?

Example (2) adding another white color:
  • -J extsub
    this one looks already perfect without any options.

  • -J extsub=0:0:0:1
    same as above with-out ant-aliasing.

  • -J extsub=0:0:0:0:0:0:255
    We make switch another color to full intensity (white) to make the subtitle appear fatter, maybe too much.

  • -J extsub=0:0:0:1:0:0:255
    The above fat one without anti-aliasing.

generating subtitle files
Please find some documentation on Arne Driescher's subrip program in the contrib/subrip/ directory or visit the project page for more information.
generating custom subtitles
Please find some documentation on Jan Panteltje's subtitler plugin in the filter/subtitler/ directory or visit the project page for more information.
Last modified: Thu May 16 12:52:34 CEST 2002