X-Git-Url: https://main.carlh.net/gitweb/?p=ardour.git;a=blobdiff_plain;f=libs%2Fardour%2Fsession_ltc.cc;h=945f96519e3f60a8c7ed1c7483eacf9b8d0c4e47;hp=d873bc07f96effd01e5ff5852523d1685c3f1061;hb=c8c6bca6587450ff64303dbc994a4cd28d6ce7aa;hpb=fd6223854d68907d250d1cab74f48e5161823b4a

diff --git a/libs/ardour/session_ltc.cc b/libs/ardour/session_ltc.cc
index d873bc07f9..945f96519e 100644
--- a/libs/ardour/session_ltc.cc
+++ b/libs/ardour/session_ltc.cc
@@ -27,11 +27,10 @@
 #include "ardour/session.h"
 #include "ardour/slave.h"
 
-#include "i18n.h"
+#include "pbd/i18n.h"
 
 using namespace std;
 using namespace ARDOUR;
-using namespace MIDI;
 using namespace PBD;
 using namespace Timecode;
 
@@ -56,7 +55,7 @@ using namespace Timecode;
  * This filter is adaptive so that fast vari-speed signals
  * will not be affected by it.
  */
-#define LTC_RISE_TIME(speed) MIN (100, MAX(40, (4000000 / ((speed==0)?1:speed) / engine().frame_rate())))
+#define LTC_RISE_TIME(speed) MIN (100, MAX(40, (4000000 / ((speed==0)?1:speed) / engine().sample_rate())))
 
 #define TV_STANDARD(tcf) \
 	(timecode_to_frames_per_second(tcf)==25.0 ? LTC_TV_625_50 : \
@@ -245,13 +244,26 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
 	/* port latency compensation:
 	 * The _generated timecode_ is offset by the port-latency,
 	 * therefore the offset depends on the direction of transport.
+	 *
+	 * latency is compensated by adding it to the timecode to
+	 * be generated. e.g. if the signal will reach the output in
+	 * N samples time from now, generate the timecode for (now + N).
+	 *
+	 * sample-sync is achieved by further calculating the difference
+	 * between the timecode and the session-transport and offsetting the
+	 * buffer.
+	 *
+	 * The timecode is generated directly in the Session process callback
+	 * using _transport_frame. It requires that the session has set the
+	 * port's playback latency to worst_playback_latency() prior to
+	 * calling ltc_tx_send_time_code_for_cycle().
 	 */
 	framepos_t cycle_start_frame;
 
 	if (current_speed < 0) {
-		cycle_start_frame = (start_frame - ltc_out_latency.max);
+		cycle_start_frame = (start_frame - ltc_out_latency.max + worst_playback_latency());
 	} else if (current_speed > 0) {
-		cycle_start_frame = (start_frame + ltc_out_latency.max);
+		cycle_start_frame = (start_frame + ltc_out_latency.max - worst_playback_latency());
 	} else {
 		/* There is no need to compensate for latency when not rolling
 		 * rather send the accurate NOW timecode
@@ -496,7 +508,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
 
 		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: now: %1 trs: %2 toff %3\n", cycle_start_frame, tc_sample_start, soff));
 
-		uint32_t cyc_off;
+		int32_t cyc_off;
 		if (soff < 0 || soff >= fptcf) {
 			/* session framerate change between (2) and now */
 			ltc_tx_reset();
@@ -532,7 +544,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
 			restarting = true;
 		}
 
-		if (cyc_off >= 0 && cyc_off <= nframes) {
+		if (cyc_off >= 0 && cyc_off <= (int32_t) nframes) {
 			/* offset in this cycle */
 			txf= rint(cyc_off / fabs(ltc_speed));
 			memset(out, 0, cyc_off * sizeof(Sample));
@@ -565,7 +577,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
 		 * To do better than this, resampling (or a rewrite of the
 		 * encoder) is required.
 		 */
-		ltc_speed -= ((ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) / engine().frame_rate();
+		ltc_speed -= ((ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) / engine().sample_rate();
 	}