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