ardour/livetrax
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Another step towards fixing MIDI Clock sync

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* Fix reset on timeout: Reset needs to be called before
  processing any messages.
* use DLL to compute BPM (remove 1st order LPF)
* set BPM before calculating ppqn
* Fix speed at 1.0, change BPM only. MIDI clock must
  vari-speed (which changes pitch). MIDI clock is acts as
  "Conductor" that specifies when a beat happens at a given
  wall-clock time. timecode moves at speed 1.0 only the BPM
  changes.
This commit is contained in:
Robin Gareus 2023-02-22 18:37:39 +01:00
parent 93b68fea89
commit 52cfa9ff19
Signed by: rgareus
GPG Key ID: A090BCE02CF57F04
1 changed files with 13 additions and 27 deletions
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40
libs/ardour/midi_clock_slave.cc
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@ -129,8 +129,6 @@ MIDIClock_TransportMaster::pre_process (MIDI::pframes_t nframes, samplepos_t now
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("preprocess with lt = %1 @ %2, running ? %3\n", current.timestamp, now, _running));
_midi_port->read_and_parse_entire_midi_buffer_with_no_speed_adjustment (nframes, parser, now);
/* no clock messages ever, or no clock messages for 1/4 second ? conclude that its stopped */
if (!current.timestamp || one_ppqn_in_samples == 0 || (now > current.timestamp && ((now - current.timestamp) > (ENGINE->sample_rate() / 4)))) {
@ -140,9 +138,10 @@ MIDIClock_TransportMaster::pre_process (MIDI::pframes_t nframes, samplepos_t now
midi_clock_count = 0;
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("No MIDI Clock messages received for some time, stopping! ts = %1 @ %2 ppqn = %3\n", current.timestamp, now, one_ppqn_in_samples));
return;
}
_midi_port->read_and_parse_entire_midi_buffer_with_no_speed_adjustment (nframes, parser, now);
if (session_pos) {
const samplepos_t current_pos = current.position + ((now - current.timestamp) * current.speed);
_current_delta = current_pos - *session_pos;
@ -223,7 +222,7 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
e2 = timestamp - current.timestamp;
const samplecnt_t samples_per_quarter = e2 * 24;
const samplecnt_t samples_per_quarter = e2 * ppqn;
double bpm = (ENGINE->sample_rate() * 60.0) / samples_per_quarter;
if (bpm < 1 || bpm > 999) {
@ -255,43 +254,30 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
t1 += b * e + e2;
e2 += c * e;
const double samples_per_quarter = (timestamp - current.timestamp) * 24.0;
const double instantaneous_bpm = (ENGINE->sample_rate() * 60.0) / samples_per_quarter;
const double samples_per_quarter = (t1 - t0) * ppqn;
const double predicted_clock_interval_in_samples = (t1 - t0) * 24;
_bpm = (ENGINE->sample_rate() * 60.0) / samples_per_quarter;
calculate_filter_coefficients (_bpm);
/* _speed is relative to session tempo map */
double speed = predicted_clock_interval_in_samples / one_ppqn_in_samples;
/* _bpm (really, _qpm) is absolute */
/* detect substantial changes in apparent tempo (defined as a
* change of more than 20% of the current tempo.
/* when rolling speed is always 1.0. The transport moves at wall-clock
* speed. What changes is the music-time (BPM), not the speed.
*/
const double lpf_coeff = 0.063;
if (fabs (instantaneous_bpm - _bpm) > (0.20 * _bpm)) {
_bpm = instantaneous_bpm;
} else {
_bpm += lpf_coeff * (instantaneous_bpm - _bpm);
if (TransportMasterManager::instance().current().get() == this) {
/* TODO always set tempo, even when there is a map */
_session->maybe_update_tempo_from_midiclock_tempo (_bpm);
}
calculate_filter_coefficients (_bpm);
calculate_one_ppqn_in_samples_at (current.position);
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);
current.update (current.position + one_ppqn_in_samples, timestamp, 1.0);
} 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);
}
}
DEBUG_TRACE (DEBUG::MidiClock, string_compose (