Software

• Install srttool

  apt-get install subtitleripper

Timeshifting

$ cat old.srt | srttool -d $offset_in_seconds > new.rt

Merging 2CD srts

$ CD1_FILE="La Dolce Vita CD1.1960.avi"
$ CD1_LENGTH=$(mplayer -identify -frames 0 -ao null -vo null "$CD1_FILE" 2> /dev/null  | grep ID_LENGTH | cut -d'=' -f2)
$ (cat CD1.srt ; cat CD2.srt | srttool -d $CD1_LENGTH ) | srttool -r > CD.srt