revert 8ca546e - original version was correct (note added)

1 files changed, 15 insertions, 2 deletions

diff --git a/libs/ardour/session_ltc.cc b/libs/ardour/session_ltc.cc
index 1c05f61b22..1ac2681641 100644
--- a/libs/ardour/session_ltc.cc
+++ b/libs/ardour/session_ltc.cc
@@ -244,13 +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);
-	} else if (current_speed > 0) {
 		cycle_start_frame = (start_frame - ltc_out_latency.max);
+	} else if (current_speed > 0) {
+		cycle_start_frame = (start_frame + ltc_out_latency.max);
 	} else {
 		/* There is no need to compensate for latency when not rolling
 		 * rather send the accurate NOW timecode