fix MTC slave+generator for non integer quarter_frame_duration

e.g. 44.1k [SPS] / 30 [fps] / 4 [MTC-frames per timecode-frame] = 367.5 [samples per MTC-frame]

git-svn-id: svn://localhost/ardour2/branches/3.0@14115 d708f5d6-7413-0410-9779-e7cbd77b26cf

4 files changed, 18 insertions, 13 deletions

diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 414a3204bd..a012aac599 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -1169,7 +1169,7 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	MIDI::byte mtc_msg[16];
 	MIDI::byte mtc_timecode_bits;   /* encoding of SMTPE type for MTC */
 	MIDI::byte midi_msg[16];
-	framepos_t outbound_mtc_timecode_frame;
+	double outbound_mtc_timecode_frame;
 	Timecode::Time transmitting_timecode_time;
 	int next_quarter_frame_to_send;
 
diff --git a/libs/ardour/ardour/slave.h b/libs/ardour/ardour/slave.h
index 471a632f6e..508664e31b 100644
--- a/libs/ardour/ardour/slave.h
+++ b/libs/ardour/ardour/slave.h
@@ -240,7 +240,7 @@ class TimecodeSlave : public Slave {
     virtual Timecode::TimecodeFormat apparent_timecode_format() const = 0;
 
     /* this is intended to be used by a UI and polled from a timeout. it should
-       return a string describing the current position of the TC source. it 
+       return a string describing the current position of the TC source. it
        should NOT do any computation, but should use a cached value
        of the TC source position.
     */
@@ -282,6 +282,7 @@ class MTC_Slave : public TimecodeSlave {
 
 	SafeTime       current;
 	framepos_t     mtc_frame;               /* current time */
+	double         mtc_frame_dll;
 	framepos_t     last_inbound_frame;      /* when we got it; audio clocked */
 	MIDI::byte     last_mtc_fps_byte;
 	framepos_t     window_begin;
diff --git a/libs/ardour/mtc_slave.cc b/libs/ardour/mtc_slave.cc
index b3992598d3..a1005ff953 100644
--- a/libs/ardour/mtc_slave.cc
+++ b/libs/ardour/mtc_slave.cc
@@ -56,6 +56,7 @@ MTC_Slave::MTC_Slave (Session& s, MIDI::Port& p)
 	reset_pending = 0;
 	reset_position = false;
 	mtc_frame = 0;
+	mtc_frame_dll = 0;
 	engine_dll_initstate = 0;
 	busy_guard1 = busy_guard2 = 0;
 
@@ -261,16 +262,16 @@ MTC_Slave::update_mtc_qtr (Parser& /*p*/, int which_qtr, framepos_t now)
 {
 	busy_guard1++;
 	const double qtr_d = quarter_frame_duration;
-	const framepos_t qtr = rint(qtr_d);
 
-	mtc_frame += qtr * transport_direction;
+	mtc_frame_dll += qtr_d * (double) transport_direction;
+	mtc_frame = rint(mtc_frame_dll);
 
 	DEBUG_TRACE (DEBUG::MTC, string_compose ("qtr frame %1 at %2 -> mtc_frame: %3\n", which_qtr, now, mtc_frame));
 
 	double mtc_speed = 0;
 	if (first_mtc_timestamp != 0) {
 		/* update MTC DLL and calculate speed */
-		const double e = mtc_frame - (double(transport_direction) * (double(now) - double(current.timestamp) + t0));
+		const double e = mtc_frame_dll - (double)transport_direction * ((double)now - (double)current.timestamp + t0);
 		t0 = t1;
 		t1 += b * e + e2;
 		e2 += c * e;
@@ -463,6 +464,7 @@ MTC_Slave::update_mtc_time (const byte *msg, bool was_full, framepos_t now)
 			if (first_mtc_timestamp == 0 || current.timestamp == 0) {
 				first_mtc_timestamp = now;
 				init_mtc_dll(mtc_frame, qtr);
+				mtc_frame_dll = mtc_frame;
 			}
 			current.guard1++;
 			current.position = mtc_frame;
diff --git a/libs/ardour/session_midi.cc b/libs/ardour/session_midi.cc
index 69de04de72..50a7178f1b 100644
--- a/libs/ardour/session_midi.cc
+++ b/libs/ardour/session_midi.cc
@@ -369,12 +369,14 @@ Session::send_full_time_code (framepos_t const t)
 	sample_to_timecode (t, timecode, true /* use_offset */, false /* no subframes */);
 
 	// sample-align outbound to rounded (no subframes) timecode
-	timecode_to_sample(timecode, outbound_mtc_timecode_frame, true, false);
+	framepos_t mtc_tc;
+	timecode_to_sample(timecode, mtc_tc, true, false);
+	outbound_mtc_timecode_frame = mtc_tc;
 
 	transmitting_timecode_time = timecode;
 
-	framecnt_t const quarter_frame_duration = ((framecnt_t) _frames_per_timecode_frame) >> 2;
-	if (ceil((t - outbound_mtc_timecode_frame) / quarter_frame_duration) > 0) {
+	double const quarter_frame_duration = ((framecnt_t) _frames_per_timecode_frame) / 4.0;
+	if (ceil((t - mtc_tc) / quarter_frame_duration) > 0) {
 		Timecode::increment (transmitting_timecode_time, config.get_subframes_per_frame());
 		outbound_mtc_timecode_frame += _frames_per_timecode_frame;
 	}
@@ -460,19 +462,19 @@ Session::send_midi_time_code_for_cycle (framepos_t start_frame, framepos_t end_f
 	assert (next_quarter_frame_to_send <= 7);
 
 	/* Duration of one quarter frame */
-	framecnt_t const quarter_frame_duration = ((framecnt_t) _frames_per_timecode_frame) >> 2;
+	double const quarter_frame_duration = _frames_per_timecode_frame / 4.0;
 
 	DEBUG_TRACE (DEBUG::MTC, string_compose ("TF %1 SF %2 MT %3 QF %4 QD %5\n",
 				_transport_frame, start_frame, outbound_mtc_timecode_frame,
 				next_quarter_frame_to_send, quarter_frame_duration));
 
-	if ((outbound_mtc_timecode_frame + (next_quarter_frame_to_send * quarter_frame_duration)) < _transport_frame) {
+	if (rint(outbound_mtc_timecode_frame + (next_quarter_frame_to_send * quarter_frame_duration)) < _transport_frame) {
 		send_full_time_code (_transport_frame);
 		return 0;
 	}
 
 	/* Send quarter frames for this cycle */
-	while (end_frame > (outbound_mtc_timecode_frame + (next_quarter_frame_to_send * quarter_frame_duration))) {
+	while (end_frame > rint(outbound_mtc_timecode_frame + (next_quarter_frame_to_send * quarter_frame_duration))) {
 
 		DEBUG_TRACE (DEBUG::MTC, string_compose ("next frame to send: %1\n", next_quarter_frame_to_send));
 
@@ -503,7 +505,7 @@ Session::send_midi_time_code_for_cycle (framepos_t start_frame, framepos_t end_f
 				break;
 		}
 
-		const framepos_t msg_time = outbound_mtc_timecode_frame	+ (quarter_frame_duration * next_quarter_frame_to_send);
+		const framepos_t msg_time = rint(outbound_mtc_timecode_frame	+ (quarter_frame_duration * next_quarter_frame_to_send));
 
 		// This message must fall within this block or something is broken
 		assert (msg_time >= start_frame);
@@ -538,7 +540,7 @@ Session::send_midi_time_code_for_cycle (framepos_t start_frame, framepos_t end_f
 			Timecode::increment (transmitting_timecode_time, config.get_subframes_per_frame());
 			// Re-calculate timing of first quarter frame
 			//timecode_to_sample( transmitting_timecode_time, outbound_mtc_timecode_frame, true /* use_offset */, false );
-			outbound_mtc_timecode_frame += 8 * quarter_frame_duration;
+			outbound_mtc_timecode_frame += 2.0 * _frames_per_timecode_frame;
 		}
 	}