#2 Play a specific section of a flac

[Nobody/Anonymous]

Hi !
I am tryng to write a cue sheet editor using jflac.
The cue sheets (and the flac files) are created using "Exact Audio Copy".
The purpose of my tool is to slightly adjust the indices within a cue sheet in cases when the track start is not exactly at the correct position, i.e. a track starts with the last little bit of sound from the previous track or ends with the first little bit of sound from the next track.
For a good usability, I need to be able to play e.g. the first or the last 5 seconds of a track.

How can I do this with jflac ?
I only found seek table based cueing or cue sheet processing for cue sheets contained in the flac file. But mine is external.
Are seek points the right way ? If so, how can I calculate my own seek points from the data of my cue sheet (plus or minus 5 seconds) ?

Thanks and Regards,
Markus