Get the lowest possible sync point. If it is not the first one on the **sorted**
        syncPointList, first subtitle will be converted to the one.

def _getLowestSyncPoint(self, syncPointList, subs):
        """Get the lowest possible sync point. If it is not the first one on the **sorted**
        syncPointList, first subtitle will be converted to the one."""
        if syncPointList[0].subNo == 0:
            return syncPointList[0]
        return SyncPoint(0, subs[0].start, subs[0].end)