Transcode provides a filter plugin, filter extsub.so
, 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
- This one looks not as expected without any further options.
- Shuffles the font color assignment using 1:2 looks like this, but has an ugly 3D effect.
- Shuffles the color assignment using 1:3 looks better, but shows white shadows that make the font fatter but blurry
- Shuffles the color assignment using 2:3 seems to be perfect. Nice and smooth looking letters.
- For comparison, we switch off anti-aliasing, see the difference?
Example (2) adding another white color
- This one looks already perfect without any options.
- Same as above with-out ant-aliasing.
- We make switch another color to full intensity (white) to make the subtitle appear fatter, maybe too much.
- The above fat one without anti-aliasing.