From 7c15ad099f759f2bfdb2701b96fb5335e916a15b Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 12 May 2020 00:05:42 +0200
Subject: Dummy Backend: add a MTC generator

---
 libs/backends/dummy/dummy_audiobackend.cc | 50 +++++++++++++++++++++++++++++++
 libs/backends/dummy/dummy_audiobackend.h  |  2 +-
 libs/backends/dummy/dummy_midi_seq.h      | 10 +++++--
 3 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/libs/backends/dummy/dummy_audiobackend.cc b/libs/backends/dummy/dummy_audiobackend.cc
index ca9a93e583..b42f29df84 100644
--- a/libs/backends/dummy/dummy_audiobackend.cc
+++ b/libs/backends/dummy/dummy_audiobackend.cc
@@ -896,6 +896,7 @@ DummyAudioBackend::get_latency_range (PortEngine::PortHandle port_handle, bool f
 	}
 
 	r = port->latency_range (for_playback);
+#ifndef ZERO_LATENCY
 	if (port->is_physical() && port->is_terminal()) {
 		if (port->is_input() && for_playback) {
 			const size_t l_in = _samples_per_period * .25;
@@ -910,6 +911,7 @@ DummyAudioBackend::get_latency_range (PortEngine::PortHandle port_handle, bool f
 			r.max += l_out;
 		}
 	}
+#endif
 	return r;
 }
 
@@ -1695,6 +1697,10 @@ DummyMidiPort::setup_generator (int seq_id, const float sr)
 	_midi_seq_spb = sr * .5f; // 120 BPM, beat_time 1.0 per beat.
 	_midi_seq_pos = 0;
 	_midi_seq_time = 0;
+
+	if (_midi_seq_dat && _midi_seq_dat[0].beat_time < 0) {
+	_midi_seq_spb = sr / 25; // 25fps MTC
+	}
 	return DummyMidiData::sequence_names[seq_id];
 }
 
@@ -1728,6 +1734,50 @@ void DummyMidiPort::midi_generate (const pframes_t n_samples)
 		return;
 	}
 
+	if (_midi_seq_dat[0].beat_time < 0) {
+		/* MTC generator */
+		const int audio_samples_per_video_frame = _midi_seq_spb; // sample-rate / 25
+		const int audio_samples_per_qf =  audio_samples_per_video_frame / 4;
+
+		samplepos_t tc_frame = _midi_seq_time / audio_samples_per_video_frame;
+		samplepos_t tc_sample = tc_frame * audio_samples_per_video_frame;
+		int qf = (tc_frame & 1) ? 4 : 0;
+		while (tc_sample < _midi_seq_time + n_samples) {
+			if (tc_sample >= _midi_seq_time) {
+				uint8_t buf[2];
+				buf[0] = 0xf1;
+
+				int frame  =    tc_frame % 25;
+				int second =   (tc_frame / 25) % 60;
+				int minute =  ((tc_frame / 25) / 60) % 60;
+				int hour   = (((tc_frame / 25) / 60) / 60);
+
+				switch(qf & 7) {
+					case 0: buf[1] =  0x00 |  (frame  & 0x0f); break;
+					case 1: buf[1] =  0x10 | ((frame  & 0xf0) >> 4); break;
+					case 2: buf[1] =  0x20 |  (second & 0x0f); break;
+					case 3: buf[1] =  0x30 | ((second & 0xf0) >> 4); break;
+					case 4: buf[1] =  0x40 |  (minute & 0x0f); break;
+					case 5: buf[1] =  0x50 | ((minute & 0xf0) >> 4); break;
+					case 6: buf[1] =  0x60 |  ((/* 25fps*/ 0x20 | hour) & 0x0f); break;
+					case 7: buf[1] =  0x70 | (((/* 25fps*/ 0x20 | hour) & 0xf0)>>4); break;
+				}
+				_buffer.push_back (boost::shared_ptr<DummyMidiEvent>(new DummyMidiEvent (tc_sample - _midi_seq_time, buf, 2)));
+			}
+			tc_sample += audio_samples_per_qf;
+			if (++qf == 8) {
+				++tc_frame;
+				qf = 0;
+			}
+		}
+
+		_midi_seq_time += n_samples;
+		if (_midi_seq_time >= /* 24 * 3600 * 25 */ 2160000LL * audio_samples_per_video_frame) {
+			_midi_seq_time -= 2160000LL * audio_samples_per_video_frame; // 24h @ 25fps
+		}
+		return;
+	}
+
 	while (1) {
 		const int32_t ev_beat_time = _midi_seq_dat[_midi_seq_pos].beat_time * _midi_seq_spb - _midi_seq_time;
 		if (ev_beat_time < 0) {
diff --git a/libs/backends/dummy/dummy_audiobackend.h b/libs/backends/dummy/dummy_audiobackend.h
index 58c0bc593d..2990e6980f 100644
--- a/libs/backends/dummy/dummy_audiobackend.h
+++ b/libs/backends/dummy/dummy_audiobackend.h
@@ -181,7 +181,7 @@ class DummyMidiPort : public DummyPort {
 		// midi event generator ('fake' physical inputs)
 		void midi_generate (const pframes_t n_samples);
 		float   _midi_seq_spb; // samples per beat
-		int32_t _midi_seq_time;
+		int64_t _midi_seq_time;
 		uint32_t _midi_seq_pos;
 		DummyMidiData::MIDISequence const * _midi_seq_dat;
 }; // class DummyMidiPort
diff --git a/libs/backends/dummy/dummy_midi_seq.h b/libs/backends/dummy/dummy_midi_seq.h
index 293b3c7091..e2b31ba5d7 100644
--- a/libs/backends/dummy/dummy_midi_seq.h
+++ b/libs/backends/dummy/dummy_midi_seq.h
@@ -1239,11 +1239,14 @@ static const MIDISequence s8[] = { // sysex
 	{ 8.98,  2, {0xf1, 0x72} },
 
 	/* 1 sec pause */
-	{11.00,  3, {0xff,  255, 0xff} }, // sentinel
+};
+
+static const MIDISequence s9[] = {
+	{-1.0, 0, {0} }, // MTC Generator
 };
 
 static const MIDISequence *sequences[] = {
-	s0, s1, s2, s3, s4, s5, s6, s7, s8
+	s0, s1, s2, s3, s4, s5, s6, s7, s8, s9
 };
 
 static const char *sequence_names[] = {
@@ -1255,7 +1258,8 @@ static const char *sequence_names[] = {
 	"CCs only",
 	"Aftertouch",
 	"Nonsense, Dups",
-	"MTC (4sec)"
+	"MTC (4sec)",
+	"MTC (gen)"
 };
 
 }} // namespace
-- 
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