libs/ardour/session_process.cc

   1 /*
   2     Copyright (C) 1999-2002 Paul Davis
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17
  18 */
  19
  20 #include <cmath>
  21 #include <cerrno>
  22 #include <algorithm>
  23 #include <unistd.h>
  24
  25 #include <pbd/error.h>
  26
  27 #include <glibmm/thread.h>
  28
  29 #include <ardour/ardour.h>
  30 #include <ardour/session.h>
  31 #include <ardour/timestamps.h>
  32 #include <ardour/audio_diskstream.h>
  33 #include <ardour/audioengine.h>
  34 #include <ardour/slave.h>
  35 #include <ardour/auditioner.h>
  36 #include <ardour/cycles.h>
  37 #include <ardour/cycle_timer.h>
  38
  39 #include <midi++/manager.h>
  40
  41 #include "i18n.h"
  42
  43 using namespace ARDOUR;
  44 using namespace PBD;
  45 using namespace std;
  46
  47 /** Called by the audio engine when there is work to be done with JACK.
  48  * @param nframes Number of frames to process.
  49  */
  50 void
  51 Session::process (nframes_t nframes)
  52 {
  53         MIDI::Manager::instance()->cycle_start(nframes);
  54
  55         _silent = false;
  56
  57         if (synced_to_jack() && waiting_to_start) {
  58                 if ( _engine.transport_state() == AudioEngine::TransportRolling) {
  59                         actually_start_transport ();
  60                 }
  61         }
  62
  63         if (non_realtime_work_pending()) {
  64                 if (!transport_work_requested ()) {
  65                         post_transport ();
  66                 }
  67         }
  68
  69         (this->*process_function) (nframes);
  70
  71         MIDI::Manager::instance()->cycle_end();
  72
  73         SendFeedback (); /* EMIT SIGNAL */
  74 }
  75
  76 void
  77 Session::prepare_diskstreams ()
  78 {
  79         boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
  80         for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
  81                 (*i)->prepare ();
  82         }
  83 }
  84
  85 int
  86 Session::no_roll (nframes_t nframes, nframes_t offset)
  87 {
  88         nframes_t end_frame = _transport_frame + nframes; // FIXME: varispeed + no_roll ??
  89         int ret = 0;
  90         bool declick = get_transport_declick_required();
  91         boost::shared_ptr<RouteList> r = routes.reader ();
  92
  93         if (_click_io) {
  94                 _click_io->silence (nframes, offset);
  95         }
  96
  97         if (g_atomic_int_get (&processing_prohibited)) {
  98                 for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
  99                         (*i)->silence (nframes, offset);
 100                 }
 101                 return 0;
 102         }
 103
 104         for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
 105
 106                 if ((*i)->is_hidden()) {
 107                         continue;
 108                 }
 109
 110                 (*i)->set_pending_declick (declick);
 111
 112                 if ((*i)->no_roll (nframes, _transport_frame, end_frame, offset, non_realtime_work_pending(),
 113                                    actively_recording(), declick)) {
 114                         error << string_compose(_("Session: error in no roll for %1"), (*i)->name()) << endmsg;
 115                         ret = -1;
 116                         break;
 117                 }
 118         }
 119
 120         return ret;
 121 }
 122
 123 int
 124 Session::process_routes (nframes_t nframes, nframes_t offset)
 125 {
 126         bool record_active;
 127         int  declick = get_transport_declick_required();
 128         bool rec_monitors = get_rec_monitors_input();
 129         boost::shared_ptr<RouteList> r = routes.reader ();
 130
 131         if (transport_sub_state & StopPendingCapture) {
 132                 /* force a declick out */
 133                 declick = -1;
 134         }
 135
 136         record_active = actively_recording(); // || (get_record_enabled() && get_punch_in());
 137
 138         const nframes_t start_frame = _transport_frame;
 139         const nframes_t end_frame = _transport_frame + (nframes_t)floor(nframes * _transport_speed);
 140
 141         for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
 142
 143                 int ret;
 144
 145                 if ((*i)->is_hidden()) {
 146                         continue;
 147                 }
 148
 149                 (*i)->set_pending_declick (declick);
 150
 151                 if ((ret = (*i)->roll (nframes, start_frame, end_frame, offset, declick, record_active, rec_monitors)) < 0) {
 152
 153                         /* we have to do this here. Route::roll() for an AudioTrack will have called AudioDiskstream::process(),
 154                            and the DS will expect AudioDiskstream::commit() to be called. but we're aborting from that
 155                            call path, so make sure we release any outstanding locks here before we return failure.
 156                         */
 157
 158                         boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 159                         for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
 160                                 (*ids)->recover ();
 161                         }
 162
 163                         stop_transport ();
 164                         return -1;
 165                 }
 166         }
 167
 168         return 0;
 169 }
 170
 171 int
 172 Session::silent_process_routes (nframes_t nframes, nframes_t offset)
 173 {
 174         bool record_active = actively_recording();
 175         int  declick = get_transport_declick_required();
 176         bool rec_monitors = get_rec_monitors_input();
 177         boost::shared_ptr<RouteList> r = routes.reader ();
 178
 179         if (transport_sub_state & StopPendingCapture) {
 180                 /* force a declick out */
 181                 declick = -1;
 182         }
 183
 184         const nframes_t start_frame = _transport_frame;
 185         const nframes_t end_frame = _transport_frame + lrintf(nframes * _transport_speed);
 186
 187         for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
 188
 189                 int ret;
 190
 191                 if ((*i)->is_hidden()) {
 192                         continue;
 193                 }
 194
 195                 if ((ret = (*i)->silent_roll (nframes, start_frame, end_frame, offset, record_active, rec_monitors)) < 0) {
 196
 197                         /* we have to do this here. Route::roll() for an AudioTrack will have called AudioDiskstream::process(),
 198                            and the DS will expect AudioDiskstream::commit() to be called. but we're aborting from that
 199                            call path, so make sure we release any outstanding locks here before we return failure.
 200                         */
 201
 202                         boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 203                         for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
 204                                 (*ids)->recover ();
 205                         }
 206
 207                         stop_transport ();
 208                         return -1;
 209                 }
 210         }
 211
 212         return 0;
 213 }
 214
 215 void
 216 Session::commit_diskstreams (nframes_t nframes, bool &needs_butler)
 217 {
 218         int dret;
 219         float pworst = 1.0f;
 220         float cworst = 1.0f;
 221
 222         boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 223         for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 224
 225                 if ((*i)->hidden()) {
 226                         continue;
 227                 }
 228
 229                 /* force all diskstreams not handled by a Route to call do their stuff.
 230                    Note: the diskstreams that were handled by a route will just return zero
 231                    from this call, because they know they were processed. So in fact, this
 232                    also runs commit() for every diskstream.
 233                  */
 234
 235                 if ((dret = (*i)->process (_transport_frame, nframes, 0, actively_recording(), get_rec_monitors_input())) == 0) {
 236                         if ((*i)->commit (nframes)) {
 237                                 needs_butler = true;
 238                         }
 239
 240                 } else if (dret < 0) {
 241                         (*i)->recover();
 242                 }
 243
 244                 pworst = min (pworst, (*i)->playback_buffer_load());
 245                 cworst = min (cworst, (*i)->capture_buffer_load());
 246         }
 247
 248         uint32_t pmin = g_atomic_int_get (&_playback_load);
 249         uint32_t pminold = g_atomic_int_get (&_playback_load_min);
 250         uint32_t cmin = g_atomic_int_get (&_capture_load);
 251         uint32_t cminold = g_atomic_int_get (&_capture_load_min);
 252
 253         g_atomic_int_set (&_playback_load, (uint32_t) floor (pworst * 100.0f));
 254         g_atomic_int_set (&_capture_load, (uint32_t) floor (cworst * 100.0f));
 255         g_atomic_int_set (&_playback_load_min, min (pmin, pminold));
 256         g_atomic_int_set (&_capture_load_min, min (cmin, cminold));
 257
 258         if (actively_recording()) {
 259                 set_dirty();
 260         }
 261 }
 262
 263 /** Process callback used when the auditioner is not active */
 264 void
 265 Session::process_with_events (nframes_t nframes)
 266 {
 267         Event*         ev;
 268         nframes_t this_nframes;
 269         nframes_t end_frame;
 270         nframes_t offset;
 271         bool session_needs_butler = false;
 272         nframes_t stop_limit;
 273         long           frames_moved;
 274
 275         /* make sure the auditioner is silent */
 276
 277         if (auditioner) {
 278                 auditioner->silence (nframes, 0);
 279         }
 280
 281         /* handle any pending events */
 282
 283         while (pending_events.read (&ev, 1) == 1) {
 284                 merge_event (ev);
 285         }
 286
 287         /* if we are not in the middle of a state change,
 288            and there are immediate events queued up,
 289            process them.
 290         */
 291
 292         while (!non_realtime_work_pending() && !immediate_events.empty()) {
 293                 Event *ev = immediate_events.front ();
 294                 immediate_events.pop_front ();
 295                 process_event (ev);
 296         }
 297
 298         /* Events caused a transport change, send an MTC Full Frame (SMPTE) message.
 299          * This is sent whether rolling or not, to give slaves an idea of ardour time
 300          * on locates (and allow slow slaves to position and prepare for rolling)
 301          */
 302         if (_send_smpte_update) {
 303                 send_full_time_code(nframes);
 304         }
 305
 306         if (!process_can_proceed()) {
 307                 _silent = true;
 308                 return;
 309         }
 310
 311         if (events.empty() || next_event == events.end()) {
 312                 process_without_events (nframes);
 313                 return;
 314         }
 315
 316         end_frame = _transport_frame + (nframes_t)abs(floor(nframes * _transport_speed));
 317
 318         {
 319                 Event* this_event;
 320                 Events::iterator the_next_one;
 321
 322                 if (!process_can_proceed()) {
 323                         _silent = true;
 324                         return;
 325                 }
 326
 327                 if (!_exporting && _slave) {
 328                         if (!follow_slave (nframes, 0)) {
 329                                 return;
 330                         }
 331                 }
 332
 333                 if (_transport_speed == 0) {
 334                         no_roll (nframes, 0);
 335                         return;
 336                 }
 337
 338                 send_midi_time_code_for_cycle(nframes);
 339
 340                 if (actively_recording()) {
 341                         stop_limit = max_frames;
 342                 } else {
 343
 344                         if (Config->get_stop_at_session_end()) {
 345                                 stop_limit = current_end_frame();
 346                         } else {
 347                                 stop_limit = max_frames;
 348                         }
 349                 }
 350
 351                 if (maybe_stop (stop_limit)) {
 352                         no_roll (nframes, 0);
 353                         return;
 354                 }
 355
 356                 this_event = *next_event;
 357                 the_next_one = next_event;
 358                 ++the_next_one;
 359
 360                 offset = 0;
 361
 362                 /* yes folks, here it is, the actual loop where we really truly
 363                    process some audio */
 364                 while (nframes) {
 365
 366                         this_nframes = nframes; /* real (jack) time relative */
 367                         frames_moved = (long) floor (_transport_speed * nframes); /* transport relative */
 368
 369                         /* running an event, position transport precisely to its time */
 370                         if (this_event && this_event->action_frame <= end_frame && this_event->action_frame >= _transport_frame) {
 371                                 /* this isn't quite right for reverse play */
 372                                 frames_moved = (long) (this_event->action_frame - _transport_frame);
 373                                 this_nframes = (nframes_t) abs( floor(frames_moved / _transport_speed) );
 374                         }
 375
 376                         if (this_nframes) {
 377
 378                                 click (_transport_frame, nframes, offset);
 379
 380                                 /* now process frames between now and the first event in this block */
 381                                 prepare_diskstreams ();
 382
 383                                 if (process_routes (this_nframes, offset)) {
 384                                         no_roll (nframes, 0);
 385                                         return;
 386                                 }
 387
 388                                 commit_diskstreams (this_nframes, session_needs_butler);
 389
 390                                 nframes -= this_nframes;
 391                                 offset += this_nframes;
 392
 393                                 if (frames_moved < 0) {
 394                                         decrement_transport_position (-frames_moved);
 395                                 } else {
 396                                         increment_transport_position (frames_moved);
 397                                 }
 398
 399                                 maybe_stop (stop_limit);
 400                                 check_declick_out ();
 401                         }
 402
 403                         /* now handle this event and all others scheduled for the same time */
 404
 405                         while (this_event && this_event->action_frame == _transport_frame) {
 406                                 process_event (this_event);
 407
 408                                 if (the_next_one == events.end()) {
 409                                         this_event = 0;
 410                                 } else {
 411                                         this_event = *the_next_one;
 412                                         ++the_next_one;
 413                                 }
 414                         }
 415
 416                         /* if an event left our state changing, do the right thing */
 417
 418                         if (non_realtime_work_pending()) {
 419                                 no_roll (nframes, offset);
 420                                 break;
 421                         }
 422
 423                         /* this is necessary to handle the case of seamless looping */
 424                         end_frame = _transport_frame + (nframes_t) floor (nframes * _transport_speed);
 425
 426                 }
 427
 428                 set_next_event ();
 429
 430         } /* implicit release of route lock */
 431
 432         if (session_needs_butler)
 433                 summon_butler ();
 434 }
 435
 436 void
 437 Session::reset_slave_state ()
 438 {
 439         average_slave_delta = 1800;
 440         delta_accumulator_cnt = 0;
 441         have_first_delta_accumulator = false;
 442         slave_state = Stopped;
 443 }
 444
 445 bool
 446 Session::transport_locked () const
 447 {
 448         Slave* sl = _slave;
 449
 450         if (!locate_pending() && ((Config->get_slave_source() == None) || (sl && sl->ok() && sl->locked()))) {
 451                 return true;
 452         }
 453
 454         return false;
 455 }
 456
 457 bool
 458 Session::follow_slave (nframes_t nframes, nframes_t offset)
 459 {
 460         float slave_speed;
 461         nframes_t slave_transport_frame;
 462         nframes_t this_delta;
 463         int dir;
 464         bool starting;
 465
 466         if (!_slave->ok()) {
 467                 stop_transport ();
 468                 Config->set_slave_source (None);
 469                 goto noroll;
 470         }
 471
 472         _slave->speed_and_position (slave_speed, slave_transport_frame);
 473
 474         if (!_slave->locked()) {
 475                 goto noroll;
 476         }
 477
 478         if (slave_transport_frame > _transport_frame) {
 479                 this_delta = slave_transport_frame - _transport_frame;
 480                 dir = 1;
 481         } else {
 482                 this_delta = _transport_frame - slave_transport_frame;
 483                 dir = -1;
 484         }
 485
 486         if ((starting = _slave->starting())) {
 487                 slave_speed = 0.0f;
 488         }
 489
 490 #if 0
 491         cerr << "delta = " << (int) (dir * this_delta)
 492              << " speed = " << slave_speed
 493              << " ts = " << _transport_speed
 494              << " M@ "<< slave_transport_frame << " S@ " << _transport_frame
 495              << " avgdelta = " << average_slave_delta
 496              << endl;
 497 #endif
 498
 499         if (_slave->is_always_synced() || Config->get_timecode_source_is_synced()) {
 500
 501                 /* if the TC source is synced, then we assume that its
 502                    speed is binary: 0.0 or 1.0
 503                 */
 504
 505                 if (slave_speed != 0.0f) {
 506                         slave_speed = 1.0f;
 507                 }
 508
 509         } else {
 510
 511                 /* TC source is able to drift relative to us (slave)
 512                    so we need to keep track of the drift and adjust
 513                    our speed to remain locked.
 514                 */
 515
 516                 if (delta_accumulator_cnt >= delta_accumulator_size) {
 517                         have_first_delta_accumulator = true;
 518                         delta_accumulator_cnt = 0;
 519                 }
 520
 521                 if (delta_accumulator_cnt != 0 || this_delta < _current_frame_rate) {
 522                         delta_accumulator[delta_accumulator_cnt++] = dir*this_delta;
 523                 }
 524
 525                 if (have_first_delta_accumulator) {
 526                         average_slave_delta = 0;
 527                         for (int i = 0; i < delta_accumulator_size; ++i) {
 528                                 average_slave_delta += delta_accumulator[i];
 529                         }
 530                         average_slave_delta /= delta_accumulator_size;
 531                         if (average_slave_delta < 0) {
 532                                 average_dir = -1;
 533                                 average_slave_delta = -average_slave_delta;
 534                         } else {
 535                                 average_dir = 1;
 536                         }
 537                         // cerr << "avgdelta = " << average_slave_delta*average_dir << endl;
 538                 }
 539         }
 540
 541         if (slave_speed != 0.0f) {
 542
 543                 /* slave is running */
 544
 545                 switch (slave_state) {
 546                 case Stopped:
 547                         if (_slave->requires_seekahead()) {
 548                                 slave_wait_end = slave_transport_frame + _current_frame_rate;
 549                                 locate (slave_wait_end, false, false);
 550                                 slave_state = Waiting;
 551                                 starting = true;
 552
 553                         } else {
 554
 555                                 slave_state = Running;
 556
 557                                 Location* al = _locations.auto_loop_location();
 558
 559                                 if (al && play_loop && (slave_transport_frame < al->start() || slave_transport_frame > al->end())) {
 560                                         // cancel looping
 561                                         request_play_loop(false);
 562                                 }
 563
 564                                 if (slave_transport_frame != _transport_frame) {
 565                                         locate (slave_transport_frame, false, false);
 566                                 }
 567                         }
 568                         break;
 569
 570                 case Waiting:
 571                         break;
 572
 573                 default:
 574                         break;
 575
 576                 }
 577
 578                 if (slave_state == Waiting) {
 579
 580                         // cerr << "waiting at " << slave_transport_frame << endl;
 581                         if (slave_transport_frame >= slave_wait_end) {
 582                                 // cerr << "\tstart at " << _transport_frame << endl;
 583
 584                                 slave_state = Running;
 585
 586                                 bool ok = true;
 587                                 nframes_t frame_delta = slave_transport_frame - _transport_frame;
 588
 589                                 boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 590
 591                                 for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 592                                         if (!(*i)->can_internal_playback_seek (frame_delta)) {
 593                                                 ok = false;
 594                                                 break;
 595                                         }
 596                                 }
 597
 598                                 if (ok) {
 599                                         for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 600                                                 (*i)->internal_playback_seek (frame_delta);
 601                                         }
 602                                         _transport_frame += frame_delta;
 603
 604                                 } else {
 605                                         // cerr << "cannot micro-seek\n";
 606                                         /* XXX what? */
 607                                 }
 608
 609                                 memset (delta_accumulator, 0, sizeof (nframes_t) * delta_accumulator_size);
 610                                 average_slave_delta = 0;
 611                                 this_delta = 0;
 612                         }
 613                 }
 614
 615                 if (slave_state == Running && _transport_speed == 0.0f) {
 616
 617                         // cerr << "slave starts transport\n";
 618
 619                         start_transport ();
 620                 }
 621
 622         } else {
 623
 624                 /* slave has stopped */
 625
 626                 if (_transport_speed != 0.0f) {
 627
 628                         // cerr << "slave stops transport: " << slave_speed << " frame: " << slave_transport_frame
 629                         // << " tf = " << _transport_frame
 630                         // << endl;
 631
 632                         if (Config->get_slave_source() == JACK) {
 633                                 last_stop_frame = _transport_frame;
 634                         }
 635
 636                         stop_transport();
 637                 }
 638
 639                 if (slave_transport_frame != _transport_frame) {
 640                         // cerr << "slave stopped, move to " << slave_transport_frame << endl;
 641                         force_locate (slave_transport_frame, false);
 642                 }
 643
 644                 slave_state = Stopped;
 645         }
 646
 647         if (slave_state == Running && !_slave->is_always_synced() && !Config->get_timecode_source_is_synced()) {
 648
 649
 650                 if (_transport_speed != 0.0f) {
 651
 652                         /*
 653                            note that average_dir is +1 or -1
 654                         */
 655
 656                         const float adjust_seconds = 1.0f;
 657                         float delta;
 658
 659                         //if (average_slave_delta == 0) {
 660                                 delta = this_delta;
 661                                 delta *= dir;
 662 //                      } else {
 663 //                              delta = average_slave_delta;
 664 //                              delta *= average_dir;
 665 //                      }
 666
 667                         float adjusted_speed = slave_speed +
 668                                 (delta / (adjust_seconds * _current_frame_rate));
 669
 670                         // cerr << "adjust using " << delta
 671                         // << " towards " << adjusted_speed
 672                         // << " ratio = " << adjusted_speed / slave_speed
 673                         // << " current = " << _transport_speed
 674                         // << " slave @ " << slave_speed
 675                         // << endl;
 676
 677                         request_transport_speed (adjusted_speed);
 678
 679 #if 1
 680                         if ((nframes_t) average_slave_delta > _slave->resolution()) {
 681                                 // cerr << "not locked\n";
 682                                 goto silent_motion;
 683                         }
 684 #endif
 685                 }
 686         }
 687
 688         if (!starting && !non_realtime_work_pending()) {
 689                 /* speed is set, we're locked, and good to go */
 690                 return true;
 691         }
 692
 693   silent_motion:
 694
 695         if (slave_speed && _transport_speed) {
 696
 697                 /* something isn't right, but we should move with the master
 698                    for now.
 699                 */
 700
 701                 bool need_butler;
 702
 703                 prepare_diskstreams ();
 704                 silent_process_routes (nframes, offset);
 705                 commit_diskstreams (nframes, need_butler);
 706
 707                 if (need_butler) {
 708                         summon_butler ();
 709                 }
 710
 711                 int32_t frames_moved = (int32_t) floor (_transport_speed * nframes);
 712
 713                 if (frames_moved < 0) {
 714                         decrement_transport_position (-frames_moved);
 715                 } else {
 716                         increment_transport_position (frames_moved);
 717                 }
 718
 719                 nframes_t stop_limit;
 720
 721                 if (actively_recording()) {
 722                         stop_limit = max_frames;
 723                 } else {
 724                         if (Config->get_stop_at_session_end()) {
 725                                 stop_limit = current_end_frame();
 726                         } else {
 727                                 stop_limit = max_frames;
 728                         }
 729                 }
 730
 731                 maybe_stop (stop_limit);
 732         }
 733
 734   noroll:
 735         /* don't move at all */
 736         no_roll (nframes, 0);
 737         return false;
 738 }
 739
 740 void
 741 Session::process_without_events (nframes_t nframes)
 742 {
 743         bool session_needs_butler = false;
 744         nframes_t stop_limit;
 745         long frames_moved;
 746         nframes_t offset = 0;
 747
 748         if (!process_can_proceed()) {
 749                 _silent = true;
 750                 return;
 751         }
 752
 753         if (!_exporting && _slave) {
 754                 if (!follow_slave (nframes, 0)) {
 755                         return;
 756                 }
 757
 758                 send_midi_time_code_for_cycle(nframes);
 759         }
 760
 761         if (_transport_speed == 0) {
 762                 no_roll (nframes, 0);
 763                 return;
 764         }
 765
 766         if (actively_recording()) {
 767                 stop_limit = max_frames;
 768         } else {
 769                 if (Config->get_stop_at_session_end()) {
 770                         stop_limit = current_end_frame();
 771                 } else {
 772                         stop_limit = max_frames;
 773                 }
 774         }
 775
 776         if (maybe_stop (stop_limit)) {
 777                 no_roll (nframes, 0);
 778                 return;
 779         }
 780
 781         if (maybe_sync_start (nframes, offset)) {
 782                 return;
 783         }
 784
 785         click (_transport_frame, nframes, offset);
 786
 787         prepare_diskstreams ();
 788
 789         frames_moved = (long) floor (_transport_speed * nframes);
 790
 791         if (process_routes (nframes, offset)) {
 792                 no_roll (nframes, offset);
 793                 return;
 794         }
 795
 796         commit_diskstreams (nframes, session_needs_butler);
 797
 798         if (frames_moved < 0) {
 799                 decrement_transport_position (-frames_moved);
 800         } else {
 801                 increment_transport_position (frames_moved);
 802         }
 803
 804         maybe_stop (stop_limit);
 805         check_declick_out ();
 806
 807         if (session_needs_butler)
 808                 summon_butler ();
 809 }
 810
 811 /** Process callback used when the auditioner is active.
 812  * @param nframes number of frames to process.
 813  */
 814 void
 815 Session::process_audition (nframes_t nframes)
 816 {
 817         Event* ev;
 818         boost::shared_ptr<RouteList> r = routes.reader ();
 819
 820         for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
 821                 if (!(*i)->is_hidden()) {
 822                         (*i)->silence (nframes, 0);
 823                 }
 824         }
 825
 826         /* run the auditioner, and if it says we need butler service, ask for it */
 827
 828         if (auditioner->play_audition (nframes) > 0) {
 829                 summon_butler ();
 830         }
 831
 832         /* handle pending events */
 833
 834         while (pending_events.read (&ev, 1) == 1) {
 835                 merge_event (ev);
 836         }
 837
 838         /* if we are not in the middle of a state change,
 839            and there are immediate events queued up,
 840            process them.
 841         */
 842
 843         while (!non_realtime_work_pending() && !immediate_events.empty()) {
 844                 Event *ev = immediate_events.front ();
 845                 immediate_events.pop_front ();
 846                 process_event (ev);
 847         }
 848
 849         if (!auditioner->active()) {
 850                 /* auditioner no longer active, so go back to the normal process callback */
 851                 process_function = &Session::process_with_events;
 852         }
 853 }
 854
 855 bool
 856 Session::maybe_sync_start (nframes_t& nframes, nframes_t& offset)
 857 {
 858         nframes_t sync_offset;
 859
 860         if (!waiting_for_sync_offset) {
 861                 return false;
 862         }
 863
 864         if (_engine.get_sync_offset (sync_offset) && sync_offset < nframes) {
 865
 866                 no_roll (sync_offset, 0);
 867                 nframes -= sync_offset;
 868                 offset += sync_offset;
 869                 waiting_for_sync_offset = false;
 870
 871                 if (nframes == 0) {
 872                         return true; // done
 873                 }
 874
 875         } else {
 876                 no_roll (nframes, 0);
 877                 return true; // done
 878         }
 879
 880         return false;
 881 }
 882