std::multimap<pts_t, off_t>::const_iterator
l = m_pts_to_offset.upper_bound(ts - 60 * 90000),
u = m_pts_to_offset.upper_bound(ts + 60 * 90000),
std::multimap<pts_t, off_t>::const_iterator
l = m_pts_to_offset.upper_bound(ts - 60 * 90000),
u = m_pts_to_offset.upper_bound(ts + 60 * 90000),