X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=libs%2Fardour%2Fsession_ltc.cc;h=2cd21f9afd77b63f7ff902ae1b2a0fbf34afa7a1;hb=00b703ebe8b1e65e8f50ce92c92366844fd9e351;hp=d6cc201a5c40e53126169be375d7e70fb3150359;hpb=c779f7b1b5576862d9ce3875f1db3117c4b4239e;p=ardour.git

diff --git a/libs/ardour/session_ltc.cc b/libs/ardour/session_ltc.cc
index d6cc201a5c..2cd21f9afd 100644
--- a/libs/ardour/session_ltc.cc
+++ b/libs/ardour/session_ltc.cc
@@ -31,7 +31,6 @@
 
 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
@@ -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();
 	}