DEBUG_TRACE (DEBUG::MTC, string_compose ("qtr frame %1 at %2 -> mtc_frame: %3\n", which_qtr, now, mtc_frame));
double mtc_speed = 0;
if (first_mtc_timestamp != 0) {
/* update MTC DLL and calculate speed */
DEBUG_TRACE (DEBUG::MTC, string_compose ("qtr frame %1 at %2 -> mtc_frame: %3\n", which_qtr, now, mtc_frame));
double mtc_speed = 0;
if (first_mtc_timestamp != 0) {
/* update MTC DLL and calculate speed */