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