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V.27ter modem modified to make it a little less tolerant of poor SNR, and a 

little more tolerant of big timing errors between the symbols at the far end,
and as they are received by us.
This commit is contained in:
Steve Underwood 2015-06-01 05:38:33 +08:00 committed by Brian
parent ebf2df68fa
commit f4841ca1bd
1 changed files with 3 additions and 3 deletions
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6
libs/spandsp/src/v27ter_rx.c
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@ -497,14 +497,14 @@ static __inline__ void symbol_sync(v27ter_rx_state_t *s)
s->gardner_integrate += (p + q > 0) ? s->gardner_step : -s->gardner_step;
if (abs(s->gardner_integrate) >= 256)
if (abs(s->gardner_integrate) >= 128)
{
/* This integrate and dump approach avoids rapid changes of the equalizer put step.
Rapid changes, without hysteresis, are bad. They degrade the equalizer performance
when the true symbol boundary is close to a sample boundary. */
//span_log(&s->logging, SPAN_LOG_FLOW, "Hop %d\n", s->gardner_integrate);
s->eq_put_step += (s->gardner_integrate/256);
s->total_baud_timing_correction += (s->gardner_integrate/256);
s->eq_put_step += (s->gardner_integrate/128);
s->total_baud_timing_correction += (s->gardner_integrate/128);
if (s->qam_report)
s->qam_report(s->qam_user_data, NULL, NULL, s->gardner_integrate);
s->gardner_integrate = 0;