libs/ardour/audio_track.cc

   1 /*
   2     Copyright (C) 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 <boost/scoped_array.hpp>
  21
  22 #include "pbd/enumwriter.h"
  23 #include "pbd/error.h"
  24
  25 #include "evoral/Curve.hpp"
  26
  27 #include "ardour/amp.h"
  28 #include "ardour/audio_buffer.h"
  29 #include "ardour/audio_diskstream.h"
  30 #include "ardour/audio_track.h"
  31 #include "ardour/audioplaylist.h"
  32 #include "ardour/boost_debug.h"
  33 #include "ardour/buffer_set.h"
  34 #include "ardour/delivery.h"
  35 #include "ardour/meter.h"
  36 #include "ardour/monitor_control.h"
  37 #include "ardour/playlist_factory.h"
  38 #include "ardour/processor.h"
  39 #include "ardour/profile.h"
  40 #include "ardour/region.h"
  41 #include "ardour/region_factory.h"
  42 #include "ardour/session.h"
  43 #include "ardour/session_playlists.h"
  44 #include "ardour/source.h"
  45 #include "ardour/utils.h"
  46
  47 #include "pbd/i18n.h"
  48
  49 using namespace std;
  50 using namespace ARDOUR;
  51 using namespace PBD;
  52
  53 AudioTrack::AudioTrack (Session& sess, string name, TrackMode mode)
  54         : Track (sess, name, PresentationInfo::AudioTrack, mode)
  55 {
  56 }
  57
  58 AudioTrack::~AudioTrack ()
  59 {
  60         if (_freeze_record.playlist && !_session.deletion_in_progress()) {
  61                 _freeze_record.playlist->release();
  62         }
  63 }
  64
  65 boost::shared_ptr<Diskstream>
  66 AudioTrack::create_diskstream ()
  67 {
  68         AudioDiskstream::Flag dflags = AudioDiskstream::Flag (AudioDiskstream::Recordable);
  69
  70         if (_mode == Destructive && !Profile->get_trx()) {
  71                 dflags = AudioDiskstream::Flag (dflags | AudioDiskstream::Destructive);
  72         } else if (_mode == NonLayered){
  73                 dflags = AudioDiskstream::Flag(dflags | AudioDiskstream::NonLayered);
  74         }
  75
  76         return boost::shared_ptr<AudioDiskstream> (new AudioDiskstream (_session, name(), dflags));
  77 }
  78
  79 void
  80 AudioTrack::set_diskstream (boost::shared_ptr<Diskstream> ds)
  81 {
  82         Track::set_diskstream (ds);
  83
  84         _diskstream->set_track (this);
  85         if (Profile->get_trx()) {
  86                 _diskstream->set_destructive (false);
  87         } else {
  88                 _diskstream->set_destructive (_mode == Destructive);
  89         }
  90         _diskstream->set_non_layered (_mode == NonLayered);
  91
  92         if (audio_diskstream()->deprecated_io_node) {
  93
  94                 if (!IO::connecting_legal) {
  95                         IO::ConnectingLegal.connect_same_thread (*this, boost::bind (&AudioTrack::deprecated_use_diskstream_connections, this));
  96                 } else {
  97                         deprecated_use_diskstream_connections ();
  98                 }
  99         }
 100
 101         _diskstream->set_record_enabled (false);
 102         _diskstream->request_input_monitoring (false);
 103
 104         DiskstreamChanged (); /* EMIT SIGNAL */
 105 }
 106
 107 boost::shared_ptr<AudioDiskstream>
 108 AudioTrack::audio_diskstream() const
 109 {
 110         return boost::dynamic_pointer_cast<AudioDiskstream>(_diskstream);
 111 }
 112
 113 int
 114 AudioTrack::set_mode (TrackMode m)
 115 {
 116         if (m != _mode) {
 117
 118                 if (!Profile->get_trx() && _diskstream->set_destructive (m == Destructive)) {
 119                         return -1;
 120                 }
 121
 122                 _diskstream->set_non_layered (m == NonLayered);
 123                 _mode = m;
 124
 125                 TrackModeChanged (); /* EMIT SIGNAL */
 126         }
 127
 128         return 0;
 129 }
 130
 131 bool
 132 AudioTrack::can_use_mode (TrackMode m, bool& bounce_required)
 133 {
 134         switch (m) {
 135         case NonLayered:
 136         case Normal:
 137                 bounce_required = false;
 138                 return true;
 139
 140         case Destructive:
 141                 if (Profile->get_trx()) {
 142                         return false;
 143                 } else {
 144                         return _diskstream->can_become_destructive (bounce_required);
 145                 }
 146                 break;
 147
 148         default:
 149                 return false;
 150         }
 151 }
 152
 153 int
 154 AudioTrack::deprecated_use_diskstream_connections ()
 155 {
 156         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 157
 158         if (diskstream->deprecated_io_node == 0) {
 159                 return 0;
 160         }
 161
 162         XMLProperty const * prop;
 163         XMLNode& node (*diskstream->deprecated_io_node);
 164
 165         /* don't do this more than once. */
 166
 167         diskstream->deprecated_io_node = 0;
 168
 169         if ((prop = node.property ("gain")) != 0) {
 170                 _amp->gain_control()->set_value (atof (prop->value().c_str()), PBD::Controllable::NoGroup);
 171         }
 172
 173         if ((prop = node.property ("input-connection")) != 0) {
 174                 boost::shared_ptr<Bundle> c = _session.bundle_by_name (prop->value());
 175
 176                 if (c == 0) {
 177                         error << string_compose(_("Unknown bundle \"%1\" listed for input of %2"), prop->value(), _name) << endmsg;
 178
 179                         if ((c = _session.bundle_by_name (_("in 1"))) == 0) {
 180                                 error << _("No input bundles available as a replacement")
 181                                 << endmsg;
 182                                 return -1;
 183                         } else {
 184                                 info << string_compose (_("Bundle %1 was not available - \"in 1\" used instead"), prop->value())
 185                                << endmsg;
 186                         }
 187                 }
 188
 189                 _input->connect_ports_to_bundle (c, true, this);
 190
 191         } else if ((prop = node.property ("inputs")) != 0) {
 192                 if (_input->set_ports (prop->value())) {
 193                         error << string_compose(_("improper input channel list in XML node (%1)"), prop->value()) << endmsg;
 194                         return -1;
 195                 }
 196         }
 197
 198         return 0;
 199 }
 200
 201 int
 202 AudioTrack::set_state (const XMLNode& node, int version)
 203 {
 204         XMLProperty const * prop;
 205
 206         if ((prop = node.property (X_("mode"))) != 0) {
 207                 _mode = TrackMode (string_2_enum (prop->value(), _mode));
 208         } else {
 209                 _mode = Normal;
 210         }
 211
 212         if (Profile->get_trx() && _mode == Destructive) {
 213                 /* Tracks does not support destructive tracks and trying to
 214                    handle it as a normal track would be wrong.
 215                 */
 216                 error << string_compose (_("%1: this session uses destructive tracks, which are not supported"), PROGRAM_NAME) << endmsg;
 217                 return -1;
 218         }
 219
 220         if (Track::set_state (node, version)) {
 221                 return -1;
 222         }
 223
 224         pending_state = const_cast<XMLNode*> (&node);
 225
 226         if (_session.state_of_the_state() & Session::Loading) {
 227                 _session.StateReady.connect_same_thread (*this, boost::bind (&AudioTrack::set_state_part_two, this));
 228         } else {
 229                 set_state_part_two ();
 230         }
 231
 232         return 0;
 233 }
 234
 235 XMLNode&
 236 AudioTrack::state (bool full_state)
 237 {
 238         XMLNode& root (Track::state(full_state));
 239         XMLNode* freeze_node;
 240         char buf[64];
 241
 242         if (_freeze_record.playlist) {
 243                 XMLNode* inode;
 244
 245                 freeze_node = new XMLNode (X_("freeze-info"));
 246                 freeze_node->add_property ("playlist", _freeze_record.playlist->name());
 247                 freeze_node->add_property ("state", enum_2_string (_freeze_record.state));
 248
 249                 for (vector<FreezeRecordProcessorInfo*>::iterator i = _freeze_record.processor_info.begin(); i != _freeze_record.processor_info.end(); ++i) {
 250                         inode = new XMLNode (X_("processor"));
 251                         (*i)->id.print (buf, sizeof (buf));
 252                         inode->add_property (X_("id"), buf);
 253                         inode->add_child_copy ((*i)->state);
 254
 255                         freeze_node->add_child_nocopy (*inode);
 256                 }
 257
 258                 root.add_child_nocopy (*freeze_node);
 259         }
 260
 261         root.add_property (X_("mode"), enum_2_string (_mode));
 262
 263         return root;
 264 }
 265
 266 void
 267 AudioTrack::set_state_part_two ()
 268 {
 269         XMLNode* fnode;
 270         XMLProperty const * prop;
 271         LocaleGuard lg;
 272
 273         /* This is called after all session state has been restored but before
 274            have been made ports and connections are established.
 275         */
 276
 277         if (pending_state == 0) {
 278                 return;
 279         }
 280
 281         if ((fnode = find_named_node (*pending_state, X_("freeze-info"))) != 0) {
 282
 283                 _freeze_record.state = Frozen;
 284
 285                 for (vector<FreezeRecordProcessorInfo*>::iterator i = _freeze_record.processor_info.begin(); i != _freeze_record.processor_info.end(); ++i) {
 286                         delete *i;
 287                 }
 288                 _freeze_record.processor_info.clear ();
 289
 290                 if ((prop = fnode->property (X_("playlist"))) != 0) {
 291                         boost::shared_ptr<Playlist> pl = _session.playlists->by_name (prop->value());
 292                         if (pl) {
 293                                 _freeze_record.playlist = boost::dynamic_pointer_cast<AudioPlaylist> (pl);
 294                                 _freeze_record.playlist->use();
 295                         } else {
 296                                 _freeze_record.playlist.reset ();
 297                                 _freeze_record.state = NoFreeze;
 298                         return;
 299                         }
 300                 }
 301
 302                 if ((prop = fnode->property (X_("state"))) != 0) {
 303                         _freeze_record.state = FreezeState (string_2_enum (prop->value(), _freeze_record.state));
 304                 }
 305
 306                 XMLNodeConstIterator citer;
 307                 XMLNodeList clist = fnode->children();
 308
 309                 for (citer = clist.begin(); citer != clist.end(); ++citer) {
 310                         if ((*citer)->name() != X_("processor")) {
 311                                 continue;
 312                         }
 313
 314                         if ((prop = (*citer)->property (X_("id"))) == 0) {
 315                                 continue;
 316                         }
 317
 318                         FreezeRecordProcessorInfo* frii = new FreezeRecordProcessorInfo (*((*citer)->children().front()),
 319                                                                                    boost::shared_ptr<Processor>());
 320                         frii->id = prop->value ();
 321                         _freeze_record.processor_info.push_back (frii);
 322                 }
 323         }
 324 }
 325
 326 /** @param need_butler to be set to true if this track now needs the butler, otherwise it can be left alone
 327  *  or set to false.
 328  */
 329 int
 330 AudioTrack::roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame, int declick, bool& need_butler)
 331 {
 332         Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
 333
 334         if (!lm.locked()) {
 335                 boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 336                 framecnt_t playback_distance = diskstream->calculate_playback_distance(nframes);
 337                 if (can_internal_playback_seek(::llabs(playback_distance))) {
 338                         /* TODO should declick */
 339                         internal_playback_seek(playback_distance);
 340                 }
 341                 return 0;
 342         }
 343
 344         framepos_t transport_frame;
 345         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 346
 347         if (n_outputs().n_total() == 0 && _processors.empty()) {
 348                 return 0;
 349         }
 350
 351         if (!_active) {
 352                 silence (nframes);
 353                 if (_meter_point == MeterInput && ((_monitoring_control->monitoring_choice() & MonitorInput) || _diskstream->record_enabled())) {
 354                         _meter->reset();
 355                 }
 356                 return 0;
 357         }
 358
 359         transport_frame = _session.transport_frame();
 360
 361         int dret;
 362         framecnt_t playback_distance;
 363
 364         if ((nframes = check_initial_delay (nframes, transport_frame)) == 0) {
 365
 366                 /* need to do this so that the diskstream sets its
 367                    playback distance to zero, thus causing diskstream::commit
 368                    to do nothing.
 369                 */
 370
 371                 BufferSet bufs; /* empty set, no matter - nothing will happen */
 372
 373                 dret = diskstream->process (bufs, transport_frame, 0, playback_distance, false);
 374                 need_butler = diskstream->commit (playback_distance);
 375                 return dret;
 376         }
 377
 378         _silent = false;
 379         _amp->apply_gain_automation(false);
 380
 381         BufferSet& bufs = _session.get_route_buffers (n_process_buffers ());
 382
 383         fill_buffers_with_input (bufs, _input, nframes);
 384
 385         if (_meter_point == MeterInput && ((_monitoring_control->monitoring_choice() & MonitorInput) || _diskstream->record_enabled())) {
 386                 _meter->run (bufs, start_frame, end_frame, 1.0 /*speed()*/, nframes, true);
 387         }
 388
 389         if ((dret = diskstream->process (bufs, transport_frame, nframes, playback_distance, (monitoring_state() == MonitoringDisk))) != 0) {
 390                 need_butler = diskstream->commit (playback_distance);
 391                 silence (nframes);
 392                 return dret;
 393         }
 394
 395         process_output_buffers (bufs, start_frame, end_frame, nframes, declick, (!diskstream->record_enabled() && _session.transport_rolling()));
 396
 397         for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
 398                 boost::shared_ptr<Delivery> d = boost::dynamic_pointer_cast<Delivery> (*i);
 399                 if (d) {
 400                         d->flush_buffers (nframes);
 401                 }
 402         }
 403
 404         need_butler = diskstream->commit (playback_distance);
 405
 406         return 0;
 407 }
 408
 409 int
 410 AudioTrack::export_stuff (BufferSet& buffers, framepos_t start, framecnt_t nframes,
 411                           boost::shared_ptr<Processor> endpoint, bool include_endpoint, bool for_export, bool for_freeze)
 412 {
 413         boost::scoped_array<gain_t> gain_buffer (new gain_t[nframes]);
 414         boost::scoped_array<Sample> mix_buffer (new Sample[nframes]);
 415         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 416
 417         Glib::Threads::RWLock::ReaderLock rlock (_processor_lock);
 418
 419         boost::shared_ptr<AudioPlaylist> apl = boost::dynamic_pointer_cast<AudioPlaylist>(diskstream->playlist());
 420
 421         assert(apl);
 422         assert(buffers.count().n_audio() >= 1);
 423         assert ((framecnt_t) buffers.get_audio(0).capacity() >= nframes);
 424
 425         if (apl->read (buffers.get_audio(0).data(), mix_buffer.get(), gain_buffer.get(), start, nframes) != nframes) {
 426                 return -1;
 427         }
 428
 429         uint32_t n=1;
 430         Sample* b = buffers.get_audio(0).data();
 431         BufferSet::audio_iterator bi = buffers.audio_begin();
 432         ++bi;
 433         for ( ; bi != buffers.audio_end(); ++bi, ++n) {
 434                 if (n < diskstream->n_channels().n_audio()) {
 435                         if (apl->read (bi->data(), mix_buffer.get(), gain_buffer.get(), start, nframes, n) != nframes) {
 436                                 return -1;
 437                         }
 438                         b = bi->data();
 439                 } else {
 440                         /* duplicate last across remaining buffers */
 441                         memcpy (bi->data(), b, sizeof (Sample) * nframes);
 442                 }
 443         }
 444
 445         bounce_process (buffers, start, nframes, endpoint, include_endpoint, for_export, for_freeze);
 446
 447         return 0;
 448 }
 449
 450 bool
 451 AudioTrack::bounceable (boost::shared_ptr<Processor> endpoint, bool include_endpoint) const
 452 {
 453         if (!endpoint && !include_endpoint) {
 454                 /* no processing - just read from the playlist and create new
 455                    files: always possible.
 456                 */
 457                 return true;
 458         }
 459
 460         Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
 461         uint32_t naudio = n_inputs().n_audio();
 462
 463         for (ProcessorList::const_iterator r = _processors.begin(); r != _processors.end(); ++r) {
 464
 465                 /* if we're not including the endpoint, potentially stop
 466                    right here before we test matching i/o valences.
 467                 */
 468
 469                 if (!include_endpoint && (*r) == endpoint) {
 470                         return true;
 471                 }
 472
 473                 /* ignore any processors that do routing, because we will not
 474                  * use them during a bounce/freeze/export operation.
 475                  */
 476
 477                 if ((*r)->does_routing()) {
 478                         continue;
 479                 }
 480
 481                 /* does the output from the last considered processor match the
 482                  * input to this one?
 483                  */
 484
 485                 if (naudio != (*r)->input_streams().n_audio()) {
 486                         return false;
 487                 }
 488
 489                 /* we're including the endpoint - if we just hit it,
 490                    then stop.
 491                 */
 492
 493                 if ((*r) == endpoint) {
 494                         return true;
 495                 }
 496
 497                 /* save outputs of this processor to test against inputs
 498                    of the next one.
 499                 */
 500
 501                 naudio = (*r)->output_streams().n_audio();
 502         }
 503
 504         return true;
 505 }
 506
 507 boost::shared_ptr<Region>
 508 AudioTrack::bounce (InterThreadInfo& itt)
 509 {
 510         return bounce_range (_session.current_start_frame(), _session.current_end_frame(), itt, main_outs(), false);
 511 }
 512
 513 boost::shared_ptr<Region>
 514 AudioTrack::bounce_range (framepos_t start, framepos_t end, InterThreadInfo& itt,
 515                           boost::shared_ptr<Processor> endpoint, bool include_endpoint)
 516 {
 517         vector<boost::shared_ptr<Source> > srcs;
 518         return _session.write_one_track (*this, start, end, false, srcs, itt, endpoint, include_endpoint, false, false);
 519 }
 520
 521 void
 522 AudioTrack::freeze_me (InterThreadInfo& itt)
 523 {
 524         vector<boost::shared_ptr<Source> > srcs;
 525         string new_playlist_name;
 526         boost::shared_ptr<Playlist> new_playlist;
 527         string dir;
 528         string region_name;
 529         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 530
 531         if ((_freeze_record.playlist = boost::dynamic_pointer_cast<AudioPlaylist>(diskstream->playlist())) == 0) {
 532                 return;
 533         }
 534
 535         uint32_t n = 1;
 536
 537         while (n < (UINT_MAX-1)) {
 538
 539                 string candidate;
 540
 541                 candidate = string_compose ("<F%2>%1", _freeze_record.playlist->name(), n);
 542
 543                 if (_session.playlists->by_name (candidate) == 0) {
 544                         new_playlist_name = candidate;
 545                         break;
 546                 }
 547
 548                 ++n;
 549
 550         }
 551
 552         if (n == (UINT_MAX-1)) {
 553           error << string_compose (X_("There are too many frozen versions of playlist \"%1\""
 554                             " to create another one"), _freeze_record.playlist->name())
 555                << endmsg;
 556                 return;
 557         }
 558
 559         boost::shared_ptr<Region> res;
 560
 561         if ((res = _session.write_one_track (*this, _session.current_start_frame(), _session.current_end_frame(),
 562                                         true, srcs, itt, main_outs(), false, false, true)) == 0) {
 563                 return;
 564         }
 565
 566         _freeze_record.processor_info.clear ();
 567
 568         {
 569                 Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
 570
 571                 for (ProcessorList::iterator r = _processors.begin(); r != _processors.end(); ++r) {
 572
 573                         if ((*r)->does_routing() && (*r)->active()) {
 574                                 break;
 575                         }
 576                         if (!boost::dynamic_pointer_cast<PeakMeter>(*r)) {
 577
 578                                 FreezeRecordProcessorInfo* frii  = new FreezeRecordProcessorInfo ((*r)->get_state(), (*r));
 579
 580                                 frii->id = (*r)->id();
 581
 582                                 _freeze_record.processor_info.push_back (frii);
 583
 584                                 /* now deactivate the processor, */
 585                                 if (!boost::dynamic_pointer_cast<Amp>(*r)) {
 586                                         (*r)->deactivate ();
 587                                 }
 588                         }
 589
 590                         _session.set_dirty ();
 591                 }
 592         }
 593
 594         new_playlist = PlaylistFactory::create (DataType::AUDIO, _session, new_playlist_name, false);
 595
 596         /* XXX need main outs automation state _freeze_record.pan_automation_state = _mainpanner->automation_state(); */
 597
 598         region_name = new_playlist_name;
 599
 600         /* create a new region from all filesources, keep it private */
 601
 602         PropertyList plist;
 603
 604         plist.add (Properties::start, 0);
 605         plist.add (Properties::length, srcs[0]->length(srcs[0]->timeline_position()));
 606         plist.add (Properties::name, region_name);
 607         plist.add (Properties::whole_file, true);
 608
 609         boost::shared_ptr<Region> region (RegionFactory::create (srcs, plist, false));
 610
 611         new_playlist->set_orig_track_id (id());
 612         new_playlist->add_region (region, _session.current_start_frame());
 613         new_playlist->set_frozen (true);
 614         region->set_locked (true);
 615
 616         diskstream->use_playlist (boost::dynamic_pointer_cast<AudioPlaylist>(new_playlist));
 617         diskstream->set_record_enabled (false);
 618
 619         _freeze_record.playlist->use(); // prevent deletion
 620
 621         /* reset stuff that has already been accounted for in the freeze process */
 622
 623         gain_control()->set_value (GAIN_COEFF_UNITY, Controllable::NoGroup);
 624         gain_control()->set_automation_state (Off);
 625
 626         /* XXX need to use _main_outs _panner->set_automation_state (Off); */
 627
 628         _freeze_record.state = Frozen;
 629         FreezeChange(); /* EMIT SIGNAL */
 630 }
 631
 632 void
 633 AudioTrack::unfreeze ()
 634 {
 635         if (_freeze_record.playlist) {
 636                 _freeze_record.playlist->release();
 637                 audio_diskstream()->use_playlist (_freeze_record.playlist);
 638
 639                 {
 640                         Glib::Threads::RWLock::ReaderLock lm (_processor_lock); // should this be a write lock? jlc
 641                         for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
 642                                 for (vector<FreezeRecordProcessorInfo*>::iterator ii = _freeze_record.processor_info.begin(); ii != _freeze_record.processor_info.end(); ++ii) {
 643                                         if ((*ii)->id == (*i)->id()) {
 644                                                 (*i)->set_state (((*ii)->state), Stateful::current_state_version);
 645                                                 break;
 646                                         }
 647                                 }
 648                         }
 649                 }
 650
 651                 _freeze_record.playlist.reset ();
 652                 /* XXX need to use _main_outs _panner->set_automation_state (_freeze_record.pan_automation_state); */
 653         }
 654
 655         _freeze_record.state = UnFrozen;
 656         FreezeChange (); /* EMIT SIGNAL */
 657 }
 658
 659 boost::shared_ptr<AudioFileSource>
 660 AudioTrack::write_source (uint32_t n)
 661 {
 662         boost::shared_ptr<AudioDiskstream> ds = boost::dynamic_pointer_cast<AudioDiskstream> (_diskstream);
 663         assert (ds);
 664         return ds->write_source (n);
 665 }
 666
 667 boost::shared_ptr<Diskstream>
 668 AudioTrack::diskstream_factory (XMLNode const & node)
 669 {
 670         return boost::shared_ptr<Diskstream> (new AudioDiskstream (_session, node));
 671 }