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/boost_debug.h"
  23 #include "pbd/enumwriter.h"
  24 #include "pbd/error.h"
  25
  26 #include "evoral/Curve.hpp"
  27
  28 #include "ardour/amp.h"
  29 #include "ardour/audio_buffer.h"
  30 #include "ardour/audio_diskstream.h"
  31 #include "ardour/audio_track.h"
  32 #include "ardour/audioplaylist.h"
  33 #include "ardour/buffer_set.h"
  34 #include "ardour/delivery.h"
  35 #include "ardour/meter.h"
  36 #include "ardour/playlist_factory.h"
  37 #include "ardour/processor.h"
  38 #include "ardour/profile.h"
  39 #include "ardour/region.h"
  40 #include "ardour/region_factory.h"
  41 #include "ardour/session.h"
  42 #include "ardour/session_playlists.h"
  43 #include "ardour/source.h"
  44 #include "ardour/utils.h"
  45
  46 #include "i18n.h"
  47
  48 using namespace std;
  49 using namespace ARDOUR;
  50 using namespace PBD;
  51
  52 AudioTrack::AudioTrack (Session& sess, string name, Route::Flag flag, TrackMode mode)
  53         : Track (sess, name, flag, mode)
  54 {
  55 }
  56
  57 AudioTrack::~AudioTrack ()
  58 {
  59 }
  60
  61 boost::shared_ptr<Diskstream>
  62 AudioTrack::create_diskstream ()
  63 {
  64         AudioDiskstream::Flag dflags = AudioDiskstream::Flag (AudioDiskstream::Recordable);
  65
  66         if (_mode == Destructive && !Profile->get_trx()) {
  67                 dflags = AudioDiskstream::Flag (dflags | AudioDiskstream::Destructive);
  68         } else if (_mode == NonLayered){
  69                 dflags = AudioDiskstream::Flag(dflags | AudioDiskstream::NonLayered);
  70         }
  71
  72         return boost::shared_ptr<AudioDiskstream> (new AudioDiskstream (_session, name(), dflags));
  73 }
  74
  75 void
  76 AudioTrack::set_diskstream (boost::shared_ptr<Diskstream> ds)
  77 {
  78         Track::set_diskstream (ds);
  79
  80         _diskstream->set_track (this);
  81         if (Profile->get_trx()) {
  82                 _diskstream->set_destructive (false);
  83         } else {
  84                 _diskstream->set_destructive (_mode == Destructive);
  85         }
  86         _diskstream->set_non_layered (_mode == NonLayered);
  87
  88         if (audio_diskstream()->deprecated_io_node) {
  89
  90                 if (!IO::connecting_legal) {
  91                         IO::ConnectingLegal.connect_same_thread (*this, boost::bind (&AudioTrack::deprecated_use_diskstream_connections, this));
  92                 } else {
  93                         deprecated_use_diskstream_connections ();
  94                 }
  95         }
  96
  97         _diskstream->set_record_enabled (false);
  98         _diskstream->request_input_monitoring (false);
  99
 100         DiskstreamChanged (); /* EMIT SIGNAL */
 101 }
 102
 103 boost::shared_ptr<AudioDiskstream>
 104 AudioTrack::audio_diskstream() const
 105 {
 106         return boost::dynamic_pointer_cast<AudioDiskstream>(_diskstream);
 107 }
 108
 109 int
 110 AudioTrack::set_mode (TrackMode m)
 111 {
 112         if (m != _mode) {
 113
 114                 if (!Profile->get_trx() && _diskstream->set_destructive (m == Destructive)) {
 115                         return -1;
 116                 }
 117
 118                 _diskstream->set_non_layered (m == NonLayered);
 119                 _mode = m;
 120
 121                 TrackModeChanged (); /* EMIT SIGNAL */
 122         }
 123
 124         return 0;
 125 }
 126
 127 bool
 128 AudioTrack::can_use_mode (TrackMode m, bool& bounce_required)
 129 {
 130         switch (m) {
 131         case NonLayered:
 132         case Normal:
 133                 bounce_required = false;
 134                 return true;
 135
 136         case Destructive:
 137                 if (Profile->get_trx()) {
 138                         return false;
 139                 } else {
 140                         return _diskstream->can_become_destructive (bounce_required);
 141                 }
 142                 break;
 143
 144         default:
 145                 return false;
 146         }
 147 }
 148
 149 int
 150 AudioTrack::deprecated_use_diskstream_connections ()
 151 {
 152         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 153
 154         if (diskstream->deprecated_io_node == 0) {
 155                 return 0;
 156         }
 157
 158         const XMLProperty* prop;
 159         XMLNode& node (*diskstream->deprecated_io_node);
 160
 161         /* don't do this more than once. */
 162
 163         diskstream->deprecated_io_node = 0;
 164
 165         if ((prop = node.property ("gain")) != 0) {
 166                 _amp->set_gain (atof (prop->value().c_str()), this);
 167         }
 168
 169         if ((prop = node.property ("input-connection")) != 0) {
 170                 boost::shared_ptr<Bundle> c = _session.bundle_by_name (prop->value());
 171
 172                 if (c == 0) {
 173                         error << string_compose(_("Unknown bundle \"%1\" listed for input of %2"), prop->value(), _name) << endmsg;
 174
 175                         if ((c = _session.bundle_by_name (_("in 1"))) == 0) {
 176                                 error << _("No input bundles available as a replacement")
 177                                 << endmsg;
 178                                 return -1;
 179                         } else {
 180                                 info << string_compose (_("Bundle %1 was not available - \"in 1\" used instead"), prop->value())
 181                                << endmsg;
 182                         }
 183                 }
 184
 185                 _input->connect_ports_to_bundle (c, true, this);
 186
 187         } else if ((prop = node.property ("inputs")) != 0) {
 188                 if (_input->set_ports (prop->value())) {
 189                         error << string_compose(_("improper input channel list in XML node (%1)"), prop->value()) << endmsg;
 190                         return -1;
 191                 }
 192         }
 193
 194         return 0;
 195 }
 196
 197 int
 198 AudioTrack::set_state (const XMLNode& node, int version)
 199 {
 200         const XMLProperty *prop;
 201
 202         if ((prop = node.property (X_("mode"))) != 0) {
 203                 _mode = TrackMode (string_2_enum (prop->value(), _mode));
 204         } else {
 205                 _mode = Normal;
 206         }
 207
 208         if (Profile->get_trx() && _mode == Destructive) {
 209                 /* Tracks does not support destructive tracks and trying to
 210                    handle it as a normal track would be wrong.
 211                 */
 212                 error << string_compose (_("%1: this session uses destructive tracks, which are not supported"), PROGRAM_NAME) << endmsg;
 213                 return -1;
 214         }
 215
 216         if (Track::set_state (node, version)) {
 217                 return -1;
 218         }
 219
 220         pending_state = const_cast<XMLNode*> (&node);
 221
 222         if (_session.state_of_the_state() & Session::Loading) {
 223                 _session.StateReady.connect_same_thread (*this, boost::bind (&AudioTrack::set_state_part_two, this));
 224         } else {
 225                 set_state_part_two ();
 226         }
 227
 228         return 0;
 229 }
 230
 231 XMLNode&
 232 AudioTrack::state (bool full_state)
 233 {
 234         XMLNode& root (Track::state(full_state));
 235         XMLNode* freeze_node;
 236         char buf[64];
 237
 238         if (_freeze_record.playlist) {
 239                 XMLNode* inode;
 240
 241                 freeze_node = new XMLNode (X_("freeze-info"));
 242                 freeze_node->add_property ("playlist", _freeze_record.playlist->name());
 243                 freeze_node->add_property ("state", enum_2_string (_freeze_record.state));
 244
 245                 for (vector<FreezeRecordProcessorInfo*>::iterator i = _freeze_record.processor_info.begin(); i != _freeze_record.processor_info.end(); ++i) {
 246                         inode = new XMLNode (X_("processor"));
 247                         (*i)->id.print (buf, sizeof (buf));
 248                         inode->add_property (X_("id"), buf);
 249                         inode->add_child_copy ((*i)->state);
 250
 251                         freeze_node->add_child_nocopy (*inode);
 252                 }
 253
 254                 root.add_child_nocopy (*freeze_node);
 255         }
 256
 257         root.add_property (X_("mode"), enum_2_string (_mode));
 258
 259         return root;
 260 }
 261
 262 void
 263 AudioTrack::set_state_part_two ()
 264 {
 265         XMLNode* fnode;
 266         XMLProperty* prop;
 267         LocaleGuard lg (X_("C"));
 268
 269         /* This is called after all session state has been restored but before
 270            have been made ports and connections are established.
 271         */
 272
 273         if (pending_state == 0) {
 274                 return;
 275         }
 276
 277         if ((fnode = find_named_node (*pending_state, X_("freeze-info"))) != 0) {
 278
 279                 _freeze_record.state = Frozen;
 280
 281                 for (vector<FreezeRecordProcessorInfo*>::iterator i = _freeze_record.processor_info.begin(); i != _freeze_record.processor_info.end(); ++i) {
 282                         delete *i;
 283                 }
 284                 _freeze_record.processor_info.clear ();
 285
 286                 if ((prop = fnode->property (X_("playlist"))) != 0) {
 287                         boost::shared_ptr<Playlist> pl = _session.playlists->by_name (prop->value());
 288                         if (pl) {
 289                                 _freeze_record.playlist = boost::dynamic_pointer_cast<AudioPlaylist> (pl);
 290                         } else {
 291                                 _freeze_record.playlist.reset ();
 292                                 _freeze_record.state = NoFreeze;
 293                         return;
 294                         }
 295                 }
 296
 297                 if ((prop = fnode->property (X_("state"))) != 0) {
 298                         _freeze_record.state = FreezeState (string_2_enum (prop->value(), _freeze_record.state));
 299                 }
 300
 301                 XMLNodeConstIterator citer;
 302                 XMLNodeList clist = fnode->children();
 303
 304                 for (citer = clist.begin(); citer != clist.end(); ++citer) {
 305                         if ((*citer)->name() != X_("processor")) {
 306                                 continue;
 307                         }
 308
 309                         if ((prop = (*citer)->property (X_("id"))) == 0) {
 310                                 continue;
 311                         }
 312
 313                         FreezeRecordProcessorInfo* frii = new FreezeRecordProcessorInfo (*((*citer)->children().front()),
 314                                                                                    boost::shared_ptr<Processor>());
 315                         frii->id = prop->value ();
 316                         _freeze_record.processor_info.push_back (frii);
 317                 }
 318         }
 319 }
 320
 321 /** @param need_butler to be set to true if this track now needs the butler, otherwise it can be left alone
 322  *  or set to false.
 323  */
 324 int
 325 AudioTrack::roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame, int declick, bool& need_butler)
 326 {
 327         Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
 328
 329         if (!lm.locked()) {
 330                 boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 331                 framecnt_t playback_distance = diskstream->calculate_playback_distance(nframes);
 332                 if (can_internal_playback_seek(::llabs(playback_distance))) {
 333                         /* TODO should declick */
 334                         internal_playback_seek(playback_distance);
 335                 }
 336                 return 0;
 337         }
 338
 339         framepos_t transport_frame;
 340         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 341
 342         if (n_outputs().n_total() == 0 && _processors.empty()) {
 343                 return 0;
 344         }
 345
 346         if (!_active) {
 347                 silence (nframes);
 348                 if (_meter_point == MeterInput && (_monitoring & MonitorInput || _diskstream->record_enabled())) {
 349                         _meter->reset();
 350                 }
 351                 return 0;
 352         }
 353
 354         transport_frame = _session.transport_frame();
 355
 356         int dret;
 357         framecnt_t playback_distance;
 358
 359         if ((nframes = check_initial_delay (nframes, transport_frame)) == 0) {
 360
 361                 /* need to do this so that the diskstream sets its
 362                    playback distance to zero, thus causing diskstream::commit
 363                    to do nothing.
 364                 */
 365
 366                 BufferSet bufs; /* empty set, no matter - nothing will happen */
 367
 368                 dret = diskstream->process (bufs, transport_frame, 0, playback_distance, false);
 369                 need_butler = diskstream->commit (playback_distance);
 370                 return dret;
 371         }
 372
 373         if (_mute_control->list() && _mute_control->automation_playback()) {
 374                 bool        valid = false;
 375                 const float mute  = _mute_control->list()->rt_safe_eval(transport_frame, valid);
 376                 if (mute >= 0.5 && !muted()) {
 377                         _mute_control->set_value(1.0);  // mute
 378                 } else if (mute < 0.5 && muted()) {
 379                         _mute_control->set_value(0.0);  // unmute
 380                 }
 381         }
 382
 383         _silent = false;
 384         _amp->apply_gain_automation(false);
 385
 386         BufferSet& bufs = _session.get_route_buffers (n_process_buffers ());
 387
 388         fill_buffers_with_input (bufs, _input, nframes);
 389
 390         if (_meter_point == MeterInput && (_monitoring & MonitorInput || _diskstream->record_enabled())) {
 391                 _meter->run (bufs, start_frame, end_frame, nframes, true);
 392         }
 393
 394         if ((dret = diskstream->process (bufs, transport_frame, nframes, playback_distance, (monitoring_state() == MonitoringDisk))) != 0) {
 395                 need_butler = diskstream->commit (playback_distance);
 396                 silence (nframes);
 397                 return dret;
 398         }
 399
 400         process_output_buffers (bufs, start_frame, end_frame, nframes, declick, (!diskstream->record_enabled() && _session.transport_rolling()));
 401
 402         for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
 403                 boost::shared_ptr<Delivery> d = boost::dynamic_pointer_cast<Delivery> (*i);
 404                 if (d) {
 405                         d->flush_buffers (nframes);
 406                 }
 407         }
 408
 409         need_butler = diskstream->commit (playback_distance);
 410
 411         return 0;
 412 }
 413
 414 int
 415 AudioTrack::export_stuff (BufferSet& buffers, framepos_t start, framecnt_t nframes,
 416                           boost::shared_ptr<Processor> endpoint, bool include_endpoint, bool for_export, bool for_freeze)
 417 {
 418         boost::scoped_array<gain_t> gain_buffer (new gain_t[nframes]);
 419         boost::scoped_array<Sample> mix_buffer (new Sample[nframes]);
 420         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 421
 422         Glib::Threads::RWLock::ReaderLock rlock (_processor_lock);
 423
 424         boost::shared_ptr<AudioPlaylist> apl = boost::dynamic_pointer_cast<AudioPlaylist>(diskstream->playlist());
 425
 426         assert(apl);
 427         assert(buffers.count().n_audio() >= 1);
 428         assert ((framecnt_t) buffers.get_audio(0).capacity() >= nframes);
 429
 430         if (apl->read (buffers.get_audio(0).data(), mix_buffer.get(), gain_buffer.get(), start, nframes) != nframes) {
 431                 return -1;
 432         }
 433
 434         uint32_t n=1;
 435         Sample* b = buffers.get_audio(0).data();
 436         BufferSet::audio_iterator bi = buffers.audio_begin();
 437         ++bi;
 438         for ( ; bi != buffers.audio_end(); ++bi, ++n) {
 439                 if (n < diskstream->n_channels().n_audio()) {
 440                         if (apl->read (bi->data(), mix_buffer.get(), gain_buffer.get(), start, nframes, n) != nframes) {
 441                                 return -1;
 442                         }
 443                         b = bi->data();
 444                 } else {
 445                         /* duplicate last across remaining buffers */
 446                         memcpy (bi->data(), b, sizeof (Sample) * nframes);
 447                 }
 448         }
 449
 450         bounce_process (buffers, start, nframes, endpoint, include_endpoint, for_export, for_freeze);
 451
 452         return 0;
 453 }
 454
 455 bool
 456 AudioTrack::bounceable (boost::shared_ptr<Processor> endpoint, bool include_endpoint) const
 457 {
 458         if (!endpoint && !include_endpoint) {
 459                 /* no processing - just read from the playlist and create new
 460                    files: always possible.
 461                 */
 462                 return true;
 463         }
 464
 465         Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
 466         uint32_t naudio = n_inputs().n_audio();
 467
 468         for (ProcessorList::const_iterator r = _processors.begin(); r != _processors.end(); ++r) {
 469
 470                 /* if we're not including the endpoint, potentially stop
 471                    right here before we test matching i/o valences.
 472                 */
 473
 474                 if (!include_endpoint && (*r) == endpoint) {
 475                         return true;
 476                 }
 477
 478                 /* ignore any processors that do routing, because we will not
 479                  * use them during a bounce/freeze/export operation.
 480                  */
 481
 482                 if ((*r)->does_routing()) {
 483                         continue;
 484                 }
 485
 486                 /* does the output from the last considered processor match the
 487                  * input to this one?
 488                  */
 489
 490                 if (naudio != (*r)->input_streams().n_audio()) {
 491                         return false;
 492                 }
 493
 494                 /* we're including the endpoint - if we just hit it,
 495                    then stop.
 496                 */
 497
 498                 if ((*r) == endpoint) {
 499                         return true;
 500                 }
 501
 502                 /* save outputs of this processor to test against inputs
 503                    of the next one.
 504                 */
 505
 506                 naudio = (*r)->output_streams().n_audio();
 507         }
 508
 509         return true;
 510 }
 511
 512 boost::shared_ptr<Region>
 513 AudioTrack::bounce (InterThreadInfo& itt)
 514 {
 515         return bounce_range (_session.current_start_frame(), _session.current_end_frame(), itt, main_outs(), false);
 516 }
 517
 518 boost::shared_ptr<Region>
 519 AudioTrack::bounce_range (framepos_t start, framepos_t end, InterThreadInfo& itt,
 520                           boost::shared_ptr<Processor> endpoint, bool include_endpoint)
 521 {
 522         vector<boost::shared_ptr<Source> > srcs;
 523         return _session.write_one_track (*this, start, end, false, srcs, itt, endpoint, include_endpoint, false, false);
 524 }
 525
 526 void
 527 AudioTrack::freeze_me (InterThreadInfo& itt)
 528 {
 529         vector<boost::shared_ptr<Source> > srcs;
 530         string new_playlist_name;
 531         boost::shared_ptr<Playlist> new_playlist;
 532         string dir;
 533         string region_name;
 534         boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 535
 536         if ((_freeze_record.playlist = boost::dynamic_pointer_cast<AudioPlaylist>(diskstream->playlist())) == 0) {
 537                 return;
 538         }
 539
 540         uint32_t n = 1;
 541
 542         while (n < (UINT_MAX-1)) {
 543
 544                 string candidate;
 545
 546                 candidate = string_compose ("<F%2>%1", _freeze_record.playlist->name(), n);
 547
 548                 if (_session.playlists->by_name (candidate) == 0) {
 549                         new_playlist_name = candidate;
 550                         break;
 551                 }
 552
 553                 ++n;
 554
 555         }
 556
 557         if (n == (UINT_MAX-1)) {
 558           error << string_compose (X_("There are too many frozen versions of playlist \"%1\""
 559                             " to create another one"), _freeze_record.playlist->name())
 560                << endmsg;
 561                 return;
 562         }
 563
 564         boost::shared_ptr<Region> res;
 565
 566         if ((res = _session.write_one_track (*this, _session.current_start_frame(), _session.current_end_frame(),
 567                                         true, srcs, itt, main_outs(), false, false, true)) == 0) {
 568                 return;
 569         }
 570
 571         _freeze_record.processor_info.clear ();
 572
 573         {
 574                 Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
 575
 576                 for (ProcessorList::iterator r = _processors.begin(); r != _processors.end(); ++r) {
 577
 578                         if ((*r)->does_routing() && (*r)->active()) {
 579                                 break;
 580                         }
 581                         if (!boost::dynamic_pointer_cast<PeakMeter>(*r)) {
 582
 583                                 FreezeRecordProcessorInfo* frii  = new FreezeRecordProcessorInfo ((*r)->get_state(), (*r));
 584
 585                                 frii->id = (*r)->id();
 586
 587                                 _freeze_record.processor_info.push_back (frii);
 588
 589                                 /* now deactivate the processor, */
 590                                 if (!boost::dynamic_pointer_cast<Amp>(*r)) {
 591                                         (*r)->deactivate ();
 592                                 }
 593                         }
 594
 595                         _session.set_dirty ();
 596                 }
 597         }
 598
 599         new_playlist = PlaylistFactory::create (DataType::AUDIO, _session, new_playlist_name, false);
 600
 601         /* XXX need main outs automation state _freeze_record.pan_automation_state = _mainpanner->automation_state(); */
 602
 603         region_name = new_playlist_name;
 604
 605         /* create a new region from all filesources, keep it private */
 606
 607         PropertyList plist;
 608
 609         plist.add (Properties::start, 0);
 610         plist.add (Properties::length, srcs[0]->length(srcs[0]->timeline_position()));
 611         plist.add (Properties::name, region_name);
 612         plist.add (Properties::whole_file, true);
 613
 614         boost::shared_ptr<Region> region (RegionFactory::create (srcs, plist, false));
 615
 616         new_playlist->set_orig_track_id (id());
 617         new_playlist->add_region (region, _session.current_start_frame());
 618         new_playlist->set_frozen (true);
 619         region->set_locked (true);
 620
 621         diskstream->use_playlist (boost::dynamic_pointer_cast<AudioPlaylist>(new_playlist));
 622         diskstream->set_record_enabled (false);
 623
 624         /* reset stuff that has already been accounted for in the freeze process */
 625
 626         set_gain (GAIN_COEFF_UNITY, this);
 627         _amp->gain_control()->set_automation_state (Off);
 628         /* XXX need to use _main_outs _panner->set_automation_state (Off); */
 629
 630         _freeze_record.state = Frozen;
 631         FreezeChange(); /* EMIT SIGNAL */
 632 }
 633
 634 void
 635 AudioTrack::unfreeze ()
 636 {
 637         if (_freeze_record.playlist) {
 638                 audio_diskstream()->use_playlist (_freeze_record.playlist);
 639
 640                 {
 641                         Glib::Threads::RWLock::ReaderLock lm (_processor_lock); // should this be a write lock? jlc
 642                         for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
 643                                 for (vector<FreezeRecordProcessorInfo*>::iterator ii = _freeze_record.processor_info.begin(); ii != _freeze_record.processor_info.end(); ++ii) {
 644                                         if ((*ii)->id == (*i)->id()) {
 645                                                 (*i)->set_state (((*ii)->state), Stateful::current_state_version);
 646                                                 break;
 647                                         }
 648                                 }
 649                         }
 650                 }
 651
 652                 _freeze_record.playlist.reset ();
 653                 /* XXX need to use _main_outs _panner->set_automation_state (_freeze_record.pan_automation_state); */
 654         }
 655
 656         _freeze_record.state = UnFrozen;
 657         FreezeChange (); /* EMIT SIGNAL */
 658 }
 659
 660 boost::shared_ptr<AudioFileSource>
 661 AudioTrack::write_source (uint32_t n)
 662 {
 663         boost::shared_ptr<AudioDiskstream> ds = boost::dynamic_pointer_cast<AudioDiskstream> (_diskstream);
 664         assert (ds);
 665         return ds->write_source (n);
 666 }
 667
 668 boost::shared_ptr<Diskstream>
 669 AudioTrack::diskstream_factory (XMLNode const & node)
 670 {
 671         return boost::shared_ptr<Diskstream> (new AudioDiskstream (_session, node));
 672 }