ardour/livetrax
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Fix initial sync to LTC with small buffersizes

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Ardour follow_slave() does nothing (not even seek) if the slave is not
locked.

The LTC-slave assumes it's locked if LTC is stable for 5 continuous
process-calls.

If the difference of Ardour's transport-position to the LTC-timecode
is large (> 2sec), the slave reset itself (assuming drift, seek don't vari-
speed).

A LTC-slave does reset does reset the locked counter.

Hence: If initially Ardour's transport differs > 2 sec and the buffersize
is small (many process-callbacks), the slave kept resetting itself
never informing Ardour that it locked to the external TC, and Ardour
never issued a seek.
This commit is contained in:
Robin Gareus 2017-07-26 22:54:31 +02:00
parent b804109e8e
commit 28c29ab22d
2 changed files with 8 additions and 7 deletions
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2
libs/ardour/ardour/slave.h
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@ -364,7 +364,7 @@ public:
bool detect_discontinuity(LTCFrameExt *, int, bool);
bool detect_ltc_fps(int, bool);
bool equal_ltc_frame_time(LTCFrame *a, LTCFrame *b);
void reset();
void reset (bool with_ts = true);
void resync_xrun();
void resync_latency();
void parse_timecode_offset();

13
libs/ardour/ltc_slave.cc
View File

@ -143,11 +143,13 @@ LTC_Slave::resync_latency()
}
void
LTC_Slave::reset()
LTC_Slave::reset (bool with_ts)
{
DEBUG_TRACE (DEBUG::LTC, "LTC reset()\n");
last_timestamp = 0;
current_delta = 0;
if (with_ts) {
last_timestamp = 0;
current_delta = 0;
}
transport_direction = 0;
ltc_speed = 0;
engine_dll_initstate = 0;
@ -466,7 +468,7 @@ LTC_Slave::speed_and_position (double& speed, framepos_t& pos)
DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames. Feeding silence to LTC parser.\n", skip));
if (skip >= 8192) skip = 8192;
unsigned char sound[8192];
memset(sound, 0, sizeof(char) * skip);
memset(sound, 0x80, sizeof(char) * skip);
ltc_decoder_write(decoder, sound, nframes, now);
} else if (skip != 0) {
/* this should never happen. it may if monotonic_cnt, now overflow on 64bit */
@ -548,9 +550,8 @@ LTC_Slave::speed_and_position (double& speed, framepos_t& pos)
if (((pos < 0) || (labs(current_delta) > 2 * session.frame_rate()))) {
DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC large drift: %1\n", current_delta));
reset();
reset(false);
speed = 0;
pos = session.transport_frame();
return true;
}