How convert .idx/.sub file in SRT file

[pali]

Hello,
can someone help me. When I have converted original Blu Ray film with DVDFAB software in MKV file I received in output next files :
1.MKV file (movie)
2.IDX file
3.SUB file 2 & 3 are for subtitle

That's OK and it works but it is not nice. When you watch the new MKV movie
letters in subtitle are white and thin

How can I convert this .idx and .sub files in SRT file. SRT file for subtitle is more pleasant then this two files (idx and sub). Everything can be changed with SRT file (letters color, letters size and letters font)

Many thanks in advance for any good help

[GregiBoy]

You will need to convert the SUB/IDX subtitles with other software such as DVDSubEdit or Subtitle Workshop.

The SUB/IDX files created are exactly as authored on the disk.

This feature is not available in Fab.