PPS_FAVG
static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
pps_shift = PPS_FAVG;
if (ntv->shift < PPS_FAVG)
pps_shiftmax = PPS_FAVG;
pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
if (pps_shift > PPS_FAVG) {
pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;