ardour/livetrax
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LTC generator: filter the signal to reduce ringing.

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git-svn-id: svn://localhost/ardour2/branches/3.0@13382 d708f5d6-7413-0410-9779-e7cbd77b26cf
This commit is contained in:
Robin Gareus 2012-11-05 15:54:18 +00:00
parent 18474a66c6
commit fb630f622d
1 changed files with 19 additions and 0 deletions
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19
libs/ardour/session_ltc.cc
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@ -39,6 +39,21 @@ using namespace Timecode;
//#define LTC_GEN_FRAMEDBUG
//#define LTC_GEN_TXDBUG
#ifndef MAX
#define MAX(a,b) ( (a) > (b) ? (a) : (b) )
#endif
#ifndef MIN
#define MIN(a,b) ( (a) < (b) ? (a) : (b) )
#endif
/* LTC signal should have a rise time of 25 us +/- 5 us.
* yet with most sound-cards a square-wave of 1-2 sample
* introduces rather some ringing and small oscillations.
* so we low-pass filter the signal a bit, depending
* on the sample-rate
*/
#define LTC_RISE_TIME MIN (150, MAX(25, (4000000 / engine().frame_rate())))
void
Session::ltc_tx_initialize()
{
@ -50,6 +65,7 @@ Session::ltc_tx_initialize()
0);
ltc_encoder_set_bufsize(ltc_encoder, nominal_frame_rate(), 23.0);
ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME);
/* buffersize for 1 LTC frame: (1 + sample-rate / fps) bytes
* usually returned by ltc_encoder_get_buffersize(encoder)
@ -178,6 +194,9 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
ltc_tx_cleanup();
return;
}
if (nominal_frame_rate() <= 48000) {
ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME);
}
ltc_enc_tcformat = cur_timecode;
ltc_tx_reset();
}