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* intime.c -- JACK internal timebase master example client.
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* To run: first start `jackd', then `jack_load intime intime 6/8,180bpm'.
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/* Copyright (C) 2003 Jack O'Quin.
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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#include <jack/jack.h>
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/* Time and tempo variables, global to the entire transport timeline.
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* There is no attempt to keep a true tempo map. The default time
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* signature is "march time": 4/4, 120bpm
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float time_beats_per_bar = 4.0;
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float time_beat_type = 4.0;
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double time_ticks_per_beat = 1920.0;
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double time_beats_per_minute = 120.0;
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/* BBT timebase callback.
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* Runs in the process thread. Realtime, must not wait.
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timebbt (jack_transport_state_t state, jack_nframes_t nframes,
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jack_position_t *pos, int new_pos, void *arg)
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double min; /* minutes since frame 0 */
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long abs_tick; /* ticks since frame 0 */
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long abs_beat; /* beats since frame 0 */
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pos->valid = JackPositionBBT;
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pos->beats_per_bar = time_beats_per_bar;
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pos->beat_type = time_beat_type;
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pos->ticks_per_beat = time_ticks_per_beat;
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pos->beats_per_minute = time_beats_per_minute;
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/* Compute BBT info from frame number. This is
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* relatively simple here, but would become complex if
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* we supported tempo or time signature changes at
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* specific locations in the transport timeline. I
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* make no claims for the numerical accuracy or
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* efficiency of these calculations. */
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min = pos->frame / ((double) pos->frame_rate * 60.0);
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abs_tick = min * pos->beats_per_minute * pos->ticks_per_beat;
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abs_beat = abs_tick / pos->ticks_per_beat;
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pos->bar = abs_beat / pos->beats_per_bar;
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pos->beat = abs_beat - (pos->bar * pos->beats_per_bar) + 1;
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pos->tick = abs_tick - (abs_beat * pos->ticks_per_beat);
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pos->bar_start_tick = pos->bar * pos->beats_per_bar *
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pos->bar++; /* adjust start to bar 1 */
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/* some debug code... */
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fprintf(stderr, "\nnew position: %" PRIu32 "\tBBT: %3"
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PRIi32 "|%" PRIi32 "|%04" PRIi32 "\n",
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pos->frame, pos->bar, pos->beat, pos->tick);
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/* Compute BBT info based on previous period. */
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pos->tick += (nframes * pos->ticks_per_beat *
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pos->beats_per_minute / (pos->frame_rate * 60));
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while (pos->tick >= pos->ticks_per_beat) {
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pos->tick -= pos->ticks_per_beat;
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if (++pos->beat > pos->beats_per_bar) {
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pos->bar_start_tick += (pos->beats_per_bar *
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/* experimental timecode callback
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* Fill in extended timecode fields using the trivial assumption that
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* we are running at nominal speed, hence with no drift.
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* It would probably be faster to compute frame_time without the
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* conditional expression. But, this demonstrates the invariant:
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* next_time[i] == frame_time[i+1], unless a reposition occurs.
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* Runs in the process thread. Realtime, must not wait.
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timecode (jack_transport_state_t state, jack_nframes_t nframes,
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jack_position_t *pos, int new_pos, void *arg)
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/* nominal transport speed */
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double seconds_per_frame = 1.0 / (double) pos->frame_rate;
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pos->valid = JackPositionTimecode;
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pos->frame_time = (new_pos?
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pos->frame * seconds_per_frame:
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pos->next_time = (pos->frame + nframes) * seconds_per_frame;
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/* after internal client loaded */
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jack_initialize (jack_client_t *client, const char *load_init)
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JackTimebaseCallback callback = timebbt;
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int rc = sscanf(load_init, " %f/%f, %lf bpm ", &time_beats_per_bar,
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&time_beat_type, &time_beats_per_minute);
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fprintf (stderr, "counting %.1f/%.1f at %.2f bpm\n",
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time_beats_per_bar, time_beat_type,
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time_beats_per_minute);
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int len = strlen(load_init);
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if ((len > 0) && (strncmp(load_init, "timecode", len) == 0))
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if (jack_set_timebase_callback(client, 0, callback, NULL) != 0) {
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fprintf (stderr, "Unable to take over timebase.\n");
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return 1; /* terminate */
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fprintf (stderr, "Internal timebase master defined.\n");
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jack_activate (client);
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return 0; /* success */
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/* before unloading */
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jack_finish (void *arg)
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fprintf (stderr, "Internal timebase client exiting.\n");