ardour/livetrax
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Towards fixing MClk transport master (#8750)

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* Honor MCLk stop messages, do not auto-start as soon as
  the tempo is locked (after 3 clock ticks).
* Retain MIDI beat position, do not rewind in ::update_midi_clock
  Do not directly start when receiving the position message,
  transport speed should be zero (regardless of clock speed),
  until the "continue" message arrives.
* Mclk start needs to rewind (not reset)

There is still an issue with start, when
_session->transport_sample() is not zero. Ardour ends up
constantly locating, rolling for a short time and re-syncing
by locating again.
This commit is contained in:
Robin Gareus 2023-02-19 15:16:43 +01:00
parent e83898cf88
commit cf0b119b45
Signed by: rgareus
GPG Key ID: A090BCE02CF57F04
1 changed files with 26 additions and 19 deletions
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43
libs/ardour/midi_clock_slave.cc
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@ -68,8 +68,7 @@ MIDIClock_TransportMaster::~MIDIClock_TransportMaster()
void
MIDIClock_TransportMaster::init ()
{
midi_clock_count = 0;
current.reset ();
reset (false);
resync_latency (false);
}
@ -210,7 +209,7 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
/* second 0xf8 message after start/reset has arrived */
first_timestamp = timestamp;
current.update (0, timestamp, 0);
current.update (current.position, timestamp, 0);
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("first clock message after start received @ %1\n", timestamp));
@ -228,7 +227,7 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
double bpm = (ENGINE->sample_rate() * 60.0) / samples_per_quarter;
if (bpm < 1 || bpm > 999) {
current.update (0, timestamp, 0);
current.update (current.position, timestamp, 0);
midi_clock_count = 1; /* start over */
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("BPM is out of bounds (%1)\n", timestamp, current.timestamp));
} else {
@ -242,7 +241,7 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
t1 = t0 + e2; /* timestamp we predict for the next 0xf8 clock message */
midi_clock_count++;
current.update (one_ppqn_in_samples + midi_port_latency.max, timestamp, 0);
current.update (current.position + one_ppqn_in_samples + midi_port_latency.max, timestamp, 0);
}
} else {
@ -281,15 +280,14 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
calculate_filter_coefficients (_bpm);
// need at least two clock events to compute speed
if (!_running) {
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("start mclock running with speed = %1\n", (t1 - t0) / one_ppqn_in_samples));
_running = true;
}
midi_clock_count++;
if (_running) {
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("mclock running with speed = %1 bpm = %2\n", (t1 - t0) / one_ppqn_in_samples, _bpm));
current.update (current.position + one_ppqn_in_samples, timestamp, speed);
} else {
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("mclock stopped speed = %1 bpm = %2\n", (t1 - t0) / one_ppqn_in_samples, _bpm));
current.update (current.position, timestamp, 0);
}
if (TransportMasterManager::instance().current().get() == this) {
_session->maybe_update_tempo_from_midiclock_tempo (_bpm);
@ -321,11 +319,12 @@ MIDIClock_TransportMaster::start (Parser& /*parser*/, samplepos_t timestamp)
{
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("MIDIClock_TransportMaster got start message at time %1 engine time %2 transport_sample %3\n", timestamp, ENGINE->sample_time(), _session->transport_sample()));
if (!_running) {
reset(true);
_running = true;
current.update (_session->transport_sample(), timestamp, 0);
if (_running) {
return;
}
_running = true;
current.update (0, timestamp, 0);
}
void
@ -341,6 +340,7 @@ MIDIClock_TransportMaster::reset (bool with_position)
_running = false;
_current_delta = 0;
midi_clock_count = 0;
}
void
@ -369,7 +369,7 @@ MIDIClock_TransportMaster::stop (Parser& /*parser*/, samplepos_t timestamp)
//
// find out the last MIDI beat: go back #midi_clocks mod 6
// and lets hope the tempo didnt change in those last 6 beats :)
current.update (current.position - (midi_clock_count % 6) * one_ppqn_in_samples, 0, 0);
current.update (current.position - (midi_clock_count % 6) * one_ppqn_in_samples, current.timestamp, 0);
}
}
@ -387,12 +387,19 @@ MIDIClock_TransportMaster::position (Parser& /*parser*/, MIDI::byte* message, si
MIDI::byte msb = message[2];
assert((lsb <= 0x7f) && (msb <= 0x7f));
/* Each MIDI Beat spans 6 MIDI Clocks.
* In other words, each MIDI Beat is a 16th note (since there are 24 MIDI
* Clocks in a quarter note, therefore 4 MIDI Beats also fit in a quarter).
* So, a master can sync playback to a resolution of any particular 16th note.
*/
uint16_t position_in_sixteenth_notes = (uint16_t(msb) << 7) | uint16_t(lsb);
samplepos_t position_in_samples = calculate_song_position(position_in_sixteenth_notes);
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("Song Position: %1 samples: %2\n", position_in_sixteenth_notes, position_in_samples));
current.update (position_in_samples + midi_port_latency.max, timestamp, current.speed);
current.update (position_in_samples + midi_port_latency.max, timestamp, 0);
}
bool