The fragments a sidx box lists (version 0 or 1, media references only), in file order, with the
song-time interval of each in milliseconds. firstFragmentByte is where the first fragment starts
— the byte after the index — which the box's first_offset is relative to.
The fragments a
sidxbox lists (version 0 or 1, media references only), in file order, with the song-time interval of each in milliseconds.firstFragmentByteis where the first fragment starts — the byte after the index — which the box'sfirst_offsetis relative to.