[FFmpeg-user] understanding DVD subtitle palette (was: how to control quality of subtitles)

[Peter Münster]

On Mon, May 25 2020, Peter Münster wrote:

> - How can I get information about the palette in an MKV-file?

I've found it:
ffprobe -v debug file.mkv


> - How can I change such a palette?

The -palette option seems to work as expected. The question is now
rather, what the various viewers do with this palette, especially my
Samsung TV.

I still don't understand the meaning of the 16 values, so I've done some
tests:

- 3 samples here: http://pmrb.free.fr/tmp/ffmpeg-test/samples/
  dvbsub-hd: DVB-subtitle and HD
  dvbsub-sd: DVB-subtitle and SD
  dvbtt-sd: DVB-teletext subtitle and SD

- 5 palettes:
  pal1, 16 different colors:
        000055,005500,550000,005555,550055,555500,0000ff,00ff00
        ff0000,00ffff,ff00ff,ffff00,0000aa,00aa00,aa0000,00aaaa
  pal2, same as pal1, but with other positions:
        005500,550000,005555,550055,555500,0000ff,00ff00,ff0000
        00ffff,ff00ff,ffff00,0000aa,00aa00,aa0000,00aaaa,000055
  pal3, all black:
        000000,000000,000000,000000,000000,000000,000000,000000
        000000,000000,000000,000000,000000,000000,000000,000000
  pal4, all white:
        ffffff,ffffff,ffffff,ffffff,ffffff,ffffff,ffffff,ffffff
        ffffff,ffffff,ffffff,ffffff,ffffff,ffffff,ffffff,ffffff
  pal5, not specified, so default from ffmpeg is used:
        000000,0000ff,00ff00,ff0000,ffff00,ff00ff,00ffff,ffffff
        808000,8080ff,800080,80ff80,008080,ff8080,555555,aaaaaa

- resulting in 15 video files here:
  http://pmrb.free.fr/tmp/ffmpeg-test/results/

- viewed with 3 viewers (VLC, MPlayer and Samsung TV), resulting in 45
  screenshots here: http://pmrb.free.fr/tmp/ffmpeg-test/results/

I'll try to dig further in order to finally find a good result for the
Samsung TV. Any help would be appreciated!

Thanks,
-- 
           Peter