commit 0404c1924254c9162222dd5000a140165d21250c
Author: Miroslav Lichvar <mlichvar@redhat.com>
Date:   Thu Jan 25 15:23:44 2024 +0100

    ts2phc: Fix offset for NMEA delays over 0.5 seconds.
    
    The current code of ts2phc assumes that the NMEA RMC message is received
    within 0.5 seconds of the pulse the timestamp in the message is refering
    to. However, with most receivers NMEA messages are referenced to the
    previous pulse. This causes a 1-second error in the measured offset for
    receivers with delays over 0.5 seconds.
    
    Add a 0.5 second correction to map the whole interval between pulses to
    the preceding pulse.
    
    Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>

diff --git a/ts2phc_nmea_pps_source.c b/ts2phc_nmea_pps_source.c
index 3a4267d..274b70a 100644
--- a/ts2phc_nmea_pps_source.c
+++ b/ts2phc_nmea_pps_source.c
@@ -191,6 +191,7 @@ static int ts2phc_nmea_pps_source_getppstime(struct ts2phc_pps_source *src,
 		return -1;
 	}
 	rmc = tmv_add(rmc, duration_since_rmc);
+	rmc = tmv_add(rmc, nanoseconds_to_tmv(500000000));
 	utc_time = tmv_to_nanoseconds(rmc);
 	utc_time /= (int64_t) 1000000000;
 	*ts = tmv_to_timespec(rmc);