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Update MClk DLL, fix calculating coefficient

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For whatever reason, previously the DLL bandwidth was set
to (10 Pi bpm^-2).
This commit is contained in:
Robin Gareus 2023-02-23 17:26:05 +01:00
parent e1ef2c7e0d
commit 866876c903
Signed by: rgareus
GPG Key ID: A090BCE02CF57F04
1 changed files with 3 additions and 13 deletions
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16
libs/ardour/midi_clock_slave.cc
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@ -178,19 +178,11 @@ MIDIClock_TransportMaster::calculate_song_position(uint16_t song_position_in_six
void
MIDIClock_TransportMaster::calculate_filter_coefficients (double qpm)
{
/* Paul says: I don't understand this computation of bandwidth
*/
const double bandwidth = 2.0 / qpm;
/* Frequency of the clock messages is ENGINE->sample_rate() / * one_ppqn_in_samples, per second or in Hz */
const double freq = (double) ENGINE->sample_rate() / one_ppqn_in_samples;
const double omega = 2.0 * M_PI * bandwidth / freq;
const double omega = 2.0 * M_PI * (60 / qpm) / 24;
b = 1.4142135623730950488 * omega; // sqrt (2.0) * omega
c = omega * omega;
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("DLL coefficients: bw:%1 omega:%2 b:%3 c:%4\n", bandwidth, omega, b, c));
DEBUG_TRACE (DEBUG::MidiClock, string_compose ("DLL coefficients: omega:%1 b:%2 c:%3\n", omega, b, c));
}
void
@ -232,9 +224,8 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
} else {
_bpm = bpm;
calculate_filter_coefficients (_bpm);
/* finish DLL initialization */
calculate_filter_coefficients (500.0); // do not rely on initial bpm, but assume a realistic BW
t0 = timestamp;
t1 = t0 + e2; /* timestamp we predict for the next 0xf8 clock message */
@ -257,7 +248,6 @@ MIDIClock_TransportMaster::update_midi_clock (Parser& /*parser*/, samplepos_t ti
const double samples_per_quarter = (t1 - t0) * ppqn;
_bpm = (ENGINE->sample_rate() * 60.0) / samples_per_quarter;
calculate_filter_coefficients (_bpm);
/* when rolling speed is always 1.0. The transport moves at wall-clock
* speed. What changes is the music-time (BPM), not the speed.