rollback to 3428, before the mysterious removal of libs/* at 3431/3432

git-svn-id: svn://localhost/ardour2/branches/3.0@3435 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 886 insertions, 0 deletions

diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
new file mode 100644
index 0000000000..d6890b31ae
--- /dev/null
+++ b/libs/ardour/session_process.cc
@@ -0,0 +1,886 @@
+/*
+    Copyright (C) 1999-2002 Paul Davis 
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include <cmath>
+#include <cerrno>
+#include <algorithm>
+#include <unistd.h>
+
+#include <pbd/error.h>
+
+#include <glibmm/thread.h>
+
+#include <ardour/ardour.h>
+#include <ardour/session.h>
+#include <ardour/timestamps.h>
+#include <ardour/audio_diskstream.h>
+#include <ardour/audioengine.h>
+#include <ardour/slave.h>
+#include <ardour/auditioner.h>
+#include <ardour/cycles.h>
+#include <ardour/cycle_timer.h>
+
+#include <midi++/manager.h>
+
+#include "i18n.h"
+
+using namespace ARDOUR;
+using namespace PBD;
+using namespace std;
+
+/** Called by the audio engine when there is work to be done with JACK.
+ * @param nframes Number of frames to process.
+ */
+void
+Session::process (nframes_t nframes)
+{
+	MIDI::Manager::instance()->cycle_start(nframes);
+
+	_silent = false;
+
+	if (synced_to_jack() && waiting_to_start) {
+		if ( _engine.transport_state() == AudioEngine::TransportRolling) {
+			actually_start_transport ();
+		}
+	}
+
+	if (non_realtime_work_pending()) {
+		if (!transport_work_requested ()) {
+			post_transport ();
+		} 
+	} 
+	
+	(this->*process_function) (nframes);
+	
+	MIDI::Manager::instance()->cycle_end();
+
+	SendFeedback (); /* EMIT SIGNAL */
+}
+
+void
+Session::prepare_diskstreams ()
+{
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
+		(*i)->prepare ();
+	}
+}
+
+int
+Session::no_roll (nframes_t nframes, nframes_t offset)
+{
+	nframes_t end_frame = _transport_frame + nframes; // FIXME: varispeed + no_roll ??
+	int ret = 0;
+	bool declick = get_transport_declick_required();
+	boost::shared_ptr<RouteList> r = routes.reader ();
+
+	if (_click_io) {
+		_click_io->silence (nframes, offset);
+	}
+
+	if (g_atomic_int_get (&processing_prohibited)) {
+		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+			(*i)->silence (nframes, offset);
+		}
+		return 0;
+	}
+
+	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+		
+		if ((*i)->is_hidden()) {
+			continue;
+		}
+		
+		(*i)->set_pending_declick (declick);
+		
+		if ((*i)->no_roll (nframes, _transport_frame, end_frame, offset, non_realtime_work_pending(), 
+				   actively_recording(), declick)) {
+			error << string_compose(_("Session: error in no roll for %1"), (*i)->name()) << endmsg;
+			ret = -1;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+int
+Session::process_routes (nframes_t nframes, nframes_t offset)
+{
+	bool record_active;
+	int  declick = get_transport_declick_required();
+	bool rec_monitors = get_rec_monitors_input();
+	boost::shared_ptr<RouteList> r = routes.reader ();
+
+	if (transport_sub_state & StopPendingCapture) {
+		/* force a declick out */
+		declick = -1;
+	}
+
+	record_active = actively_recording(); // || (get_record_enabled() && get_punch_in());
+
+	const nframes_t start_frame = _transport_frame;
+	const nframes_t end_frame = _transport_frame + (nframes_t)floor(nframes * _transport_speed);
+
+	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+
+		int ret;
+
+		if ((*i)->is_hidden()) {
+			continue;
+		}
+
+		(*i)->set_pending_declick (declick);
+
+		if ((ret = (*i)->roll (nframes, start_frame, end_frame, offset, declick, record_active, rec_monitors)) < 0) {
+
+			/* we have to do this here. Route::roll() for an AudioTrack will have called AudioDiskstream::process(),
+			   and the DS will expect AudioDiskstream::commit() to be called. but we're aborting from that
+			   call path, so make sure we release any outstanding locks here before we return failure.
+			*/
+
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
+				(*ids)->recover ();
+			}
+
+			stop_transport ();
+			return -1;
+		} 
+	}
+
+	return 0;
+}
+
+int
+Session::silent_process_routes (nframes_t nframes, nframes_t offset)
+{
+	bool record_active = actively_recording();
+	int  declick = get_transport_declick_required();
+	bool rec_monitors = get_rec_monitors_input();
+	boost::shared_ptr<RouteList> r = routes.reader ();
+
+	if (transport_sub_state & StopPendingCapture) {
+		/* force a declick out */
+		declick = -1;
+	}
+	
+	const nframes_t start_frame = _transport_frame;
+	const nframes_t end_frame = _transport_frame + lrintf(nframes * _transport_speed);
+
+	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+
+		int ret;
+
+		if ((*i)->is_hidden()) {
+			continue;
+		}
+
+		if ((ret = (*i)->silent_roll (nframes, start_frame, end_frame, offset, record_active, rec_monitors)) < 0) {
+			
+			/* we have to do this here. Route::roll() for an AudioTrack will have called AudioDiskstream::process(),
+			   and the DS will expect AudioDiskstream::commit() to be called. but we're aborting from that
+			   call path, so make sure we release any outstanding locks here before we return failure.
+			*/
+
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
+				(*ids)->recover ();
+			}
+
+			stop_transport ();
+			return -1;
+		} 
+	}
+
+	return 0;
+}
+
+void
+Session::commit_diskstreams (nframes_t nframes, bool &needs_butler)
+{
+	int dret;
+	float pworst = 1.0f;
+	float cworst = 1.0f;
+
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
+
+		if ((*i)->hidden()) {
+			continue;
+		}
+		
+		/* force all diskstreams not handled by a Route to call do their stuff.
+		   Note: the diskstreams that were handled by a route will just return zero
+		   from this call, because they know they were processed. So in fact, this
+		   also runs commit() for every diskstream.
+		 */
+
+		if ((dret = (*i)->process (_transport_frame, nframes, 0, actively_recording(), get_rec_monitors_input())) == 0) {
+			if ((*i)->commit (nframes)) {
+				needs_butler = true;
+			}
+
+		} else if (dret < 0) {
+			(*i)->recover();
+		}
+		
+		pworst = min (pworst, (*i)->playback_buffer_load());
+		cworst = min (cworst, (*i)->capture_buffer_load());
+	}
+
+	uint32_t pmin = g_atomic_int_get (&_playback_load);
+	uint32_t pminold = g_atomic_int_get (&_playback_load_min);
+	uint32_t cmin = g_atomic_int_get (&_capture_load);
+	uint32_t cminold = g_atomic_int_get (&_capture_load_min);
+
+	g_atomic_int_set (&_playback_load, (uint32_t) floor (pworst * 100.0f));
+	g_atomic_int_set (&_capture_load, (uint32_t) floor (cworst * 100.0f));
+	g_atomic_int_set (&_playback_load_min, min (pmin, pminold));
+	g_atomic_int_set (&_capture_load_min, min (cmin, cminold));
+
+	if (actively_recording()) {
+		set_dirty();
+	}
+}
+
+/** Process callback used when the auditioner is not active */
+void
+Session::process_with_events (nframes_t nframes)
+{
+	Event*         ev;
+	nframes_t this_nframes;
+	nframes_t end_frame;
+	nframes_t offset;
+	bool session_needs_butler = false;
+	nframes_t stop_limit;
+	long           frames_moved;
+	
+	/* make sure the auditioner is silent */
+
+	if (auditioner) {
+		auditioner->silence (nframes, 0);
+	}
+
+	/* handle any pending events */
+
+	while (pending_events.read (&ev, 1) == 1) {
+		merge_event (ev);
+	}
+
+	/* if we are not in the middle of a state change,
+	   and there are immediate events queued up,
+	   process them. 
+	*/
+
+	while (!non_realtime_work_pending() && !immediate_events.empty()) {
+		Event *ev = immediate_events.front ();
+		immediate_events.pop_front ();
+		process_event (ev);
+	}
+
+	/* Events caused a transport change, send an MTC Full Frame (SMPTE) message.
+	 * This is sent whether rolling or not, to give slaves an idea of ardour time
+	 * on locates (and allow slow slaves to position and prepare for rolling)
+	 */
+	if (_send_smpte_update) {
+		send_full_time_code(nframes);
+	}
+
+	if (!process_can_proceed()) {
+		_silent = true;
+		return;
+	}
+
+	if (events.empty() || next_event == events.end()) {
+		process_without_events (nframes);
+		return;
+	}
+
+	end_frame = _transport_frame + (nframes_t)abs(floor(nframes * _transport_speed));
+
+	{
+		Event* this_event;
+		Events::iterator the_next_one;
+		
+		if (!process_can_proceed()) {
+			_silent = true;
+			return;
+		}
+		
+		if (!_exporting && _slave) {
+			if (!follow_slave (nframes, 0)) {
+				return;
+			}
+		} 
+
+		if (_transport_speed == 0) {
+			no_roll (nframes, 0);
+			return;
+		}
+	
+		if (!_exporting) {
+			send_midi_time_code_for_cycle (nframes);
+		}
+
+		if (actively_recording()) {
+			stop_limit = max_frames;
+		} else {
+
+			if (Config->get_stop_at_session_end()) {
+				stop_limit = current_end_frame();
+			} else {
+				stop_limit = max_frames;
+			}
+		}
+
+		if (maybe_stop (stop_limit)) {
+			no_roll (nframes, 0);
+			return;
+		} 
+
+		this_event = *next_event;
+		the_next_one = next_event;
+		++the_next_one;
+
+		offset = 0;
+
+		/* yes folks, here it is, the actual loop where we really truly
+		   process some audio */
+		while (nframes) {
+
+			this_nframes = nframes; /* real (jack) time relative */
+			frames_moved = (long) floor (_transport_speed * nframes); /* transport relative */
+
+			/* running an event, position transport precisely to its time */
+			if (this_event && this_event->action_frame <= end_frame && this_event->action_frame >= _transport_frame) {
+				/* this isn't quite right for reverse play */
+				frames_moved = (long) (this_event->action_frame - _transport_frame);
+				this_nframes = (nframes_t) abs( floor(frames_moved / _transport_speed) );
+			} 
+
+			if (this_nframes) {
+				
+				click (_transport_frame, nframes, offset);
+				
+				/* now process frames between now and the first event in this block */
+				prepare_diskstreams ();
+
+				if (process_routes (this_nframes, offset)) {
+					no_roll (nframes, 0);
+					return;
+				}
+				
+				commit_diskstreams (this_nframes, session_needs_butler);
+
+				nframes -= this_nframes;
+				offset += this_nframes;
+				
+				if (frames_moved < 0) {
+					decrement_transport_position (-frames_moved);
+				} else {
+					increment_transport_position (frames_moved);
+				}
+
+				maybe_stop (stop_limit);
+				check_declick_out ();
+			}
+
+			/* now handle this event and all others scheduled for the same time */
+			
+			while (this_event && this_event->action_frame == _transport_frame) {
+				process_event (this_event);
+
+				if (the_next_one == events.end()) {
+					this_event = 0;
+				} else {
+					this_event = *the_next_one;
+					++the_next_one;
+				}
+			} 
+
+			/* if an event left our state changing, do the right thing */
+
+			if (non_realtime_work_pending()) {
+				no_roll (nframes, offset);
+				break;
+			}
+
+			/* this is necessary to handle the case of seamless looping */
+			end_frame = _transport_frame + (nframes_t) floor (nframes * _transport_speed);
+			
+		}
+
+		set_next_event ();
+
+	} /* implicit release of route lock */
+
+	if (session_needs_butler)
+		summon_butler ();
+}
+
+void
+Session::reset_slave_state ()
+{
+	average_slave_delta = 1800;
+	delta_accumulator_cnt = 0;
+	have_first_delta_accumulator = false;
+	slave_state = Stopped;
+}
+
+bool
+Session::transport_locked () const
+{
+	Slave* sl = _slave;
+
+	if (!locate_pending() && ((Config->get_slave_source() == None) || (sl && sl->ok() && sl->locked()))) {
+		return true;
+	}
+
+	return false;
+}
+
+bool
+Session::follow_slave (nframes_t nframes, nframes_t offset)
+{
+	float slave_speed;
+	nframes_t slave_transport_frame;
+	nframes_t this_delta;
+	int dir;
+	bool starting;
+
+	if (!_slave->ok()) {
+		stop_transport ();
+		Config->set_slave_source (None);
+		goto noroll;
+	}
+	
+	_slave->speed_and_position (slave_speed, slave_transport_frame);
+
+	if (!_slave->locked()) {
+		goto noroll;
+	}
+
+	if (slave_transport_frame > _transport_frame) {
+		this_delta = slave_transport_frame - _transport_frame;
+		dir = 1;
+	} else {
+		this_delta = _transport_frame - slave_transport_frame;
+		dir = -1;
+	}
+
+	if ((starting = _slave->starting())) {
+		slave_speed = 0.0f;
+	}
+
+#if 0
+	cerr << "delta = " << (int) (dir * this_delta)
+	     << " speed = " << slave_speed 
+	     << " ts = " << _transport_speed 
+	     << " M@ "<< slave_transport_frame << " S@ " << _transport_frame 
+	     << " avgdelta = " << average_slave_delta 
+	     << endl;
+#endif	
+
+	if (_slave->is_always_synced() || Config->get_timecode_source_is_synced()) {
+
+		/* if the TC source is synced, then we assume that its 
+		   speed is binary: 0.0 or 1.0
+		*/
+
+		if (slave_speed != 0.0f) {
+			slave_speed = 1.0f;
+		} 
+
+	} else {
+
+		/* TC source is able to drift relative to us (slave)
+		   so we need to keep track of the drift and adjust
+		   our speed to remain locked.
+		*/
+
+		if (delta_accumulator_cnt >= delta_accumulator_size) {
+			have_first_delta_accumulator = true;
+			delta_accumulator_cnt = 0;
+		}
+
+		if (delta_accumulator_cnt != 0 || this_delta < _current_frame_rate) {
+			delta_accumulator[delta_accumulator_cnt++] = dir*this_delta;
+		}
+		
+		if (have_first_delta_accumulator) {
+			average_slave_delta = 0;
+			for (int i = 0; i < delta_accumulator_size; ++i) {
+				average_slave_delta += delta_accumulator[i];
+			}
+			average_slave_delta /= delta_accumulator_size;
+			if (average_slave_delta < 0) {
+				average_dir = -1;
+				average_slave_delta = -average_slave_delta;
+			} else {
+				average_dir = 1;
+			}
+			// cerr << "avgdelta = " << average_slave_delta*average_dir << endl;
+		}
+	}
+
+	if (slave_speed != 0.0f) {
+
+		/* slave is running */
+
+		switch (slave_state) {
+		case Stopped:
+			if (_slave->requires_seekahead()) {
+				slave_wait_end = slave_transport_frame + _current_frame_rate;
+				locate (slave_wait_end, false, false);
+				slave_state = Waiting;
+				starting = true;
+
+			} else {
+
+				slave_state = Running;
+
+				Location* al = _locations.auto_loop_location();
+
+				if (al && play_loop && (slave_transport_frame < al->start() || slave_transport_frame > al->end())) {
+					// cancel looping
+					request_play_loop(false);
+				}
+
+				if (slave_transport_frame != _transport_frame) {
+					locate (slave_transport_frame, false, false);
+				}
+			}
+			break;
+
+		case Waiting:
+			break;
+
+		default:
+			break;
+
+		}
+
+		if (slave_state == Waiting) {
+
+			// cerr << "waiting at " << slave_transport_frame << endl;
+			if (slave_transport_frame >= slave_wait_end) {
+				// cerr << "\tstart at " << _transport_frame << endl;
+
+				slave_state = Running;
+
+				bool ok = true;
+				nframes_t frame_delta = slave_transport_frame - _transport_frame;
+
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+				
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
+					if (!(*i)->can_internal_playback_seek (frame_delta)) {
+						ok = false;
+						break;
+					}
+				}
+
+				if (ok) {
+					for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
+						(*i)->internal_playback_seek (frame_delta);
+					}
+					_transport_frame += frame_delta;
+				       
+				} else {
+					// cerr << "cannot micro-seek\n";
+					/* XXX what? */
+				}
+
+				memset (delta_accumulator, 0, sizeof (nframes_t) * delta_accumulator_size);
+				average_slave_delta = 0;
+				this_delta = 0;
+			}
+		}
+		
+		if (slave_state == Running && _transport_speed == 0.0f) {
+			
+			// cerr << "slave starts transport\n";
+			
+			start_transport ();
+		} 
+
+	} else {
+
+		/* slave has stopped */
+
+		if (_transport_speed != 0.0f) {
+
+			// cerr << "slave stops transport: " << slave_speed << " frame: " << slave_transport_frame 
+			// << " tf = " << _transport_frame
+			// << endl;
+			
+			if (Config->get_slave_source() == JACK) {
+				last_stop_frame = _transport_frame;
+			}
+
+			stop_transport();
+		}
+
+		if (slave_transport_frame != _transport_frame) {
+			// cerr << "slave stopped, move to " << slave_transport_frame << endl;
+			force_locate (slave_transport_frame, false);
+		}
+
+		slave_state = Stopped;
+	}
+
+	if (slave_state == Running && !_slave->is_always_synced() && !Config->get_timecode_source_is_synced()) {
+
+
+		if (_transport_speed != 0.0f) {
+			
+			/* 
+			   note that average_dir is +1 or -1 
+			*/
+			
+			const float adjust_seconds = 1.0f;
+			float delta;
+
+			//if (average_slave_delta == 0) {
+				delta = this_delta;
+				delta *= dir;
+//			} else {
+//				delta = average_slave_delta;
+//				delta *= average_dir;
+//			}
+
+			float adjusted_speed = slave_speed +
+				(delta / (adjust_seconds * _current_frame_rate));
+			
+			// cerr << "adjust using " << delta
+			// << " towards " << adjusted_speed
+			// << " ratio = " << adjusted_speed / slave_speed
+			// << " current = " << _transport_speed
+			// << " slave @ " << slave_speed
+			// << endl;
+			
+			request_transport_speed (adjusted_speed);
+			
+#if 1
+			if ((nframes_t) average_slave_delta > _slave->resolution()) {
+				// cerr << "not locked\n";
+				goto silent_motion;
+			}
+#endif
+		}
+	} 
+
+	if (!starting && !non_realtime_work_pending()) {
+		/* speed is set, we're locked, and good to go */
+		return true;
+	}
+
+  silent_motion:
+
+	if (slave_speed && _transport_speed) {
+
+		/* something isn't right, but we should move with the master
+		   for now.
+		*/
+
+		bool need_butler;
+		
+		prepare_diskstreams ();
+		silent_process_routes (nframes, offset);
+		commit_diskstreams (nframes, need_butler);
+
+		if (need_butler) {
+			summon_butler ();
+		}
+		
+		int32_t frames_moved = (int32_t) floor (_transport_speed * nframes);
+		
+		if (frames_moved < 0) {
+			decrement_transport_position (-frames_moved);
+		} else {
+			increment_transport_position (frames_moved);
+		}
+		
+		nframes_t stop_limit;
+		
+		if (actively_recording()) {
+			stop_limit = max_frames;
+		} else {
+			if (Config->get_stop_at_session_end()) {
+				stop_limit = current_end_frame();
+			} else {
+				stop_limit = max_frames;
+			}
+		}
+
+		maybe_stop (stop_limit);
+	}
+
+  noroll:
+	/* don't move at all */
+	no_roll (nframes, 0);
+	return false;
+}
+
+void
+Session::process_without_events (nframes_t nframes)
+{
+	bool session_needs_butler = false;
+	nframes_t stop_limit;
+	long frames_moved;
+	nframes_t offset = 0;
+
+	if (!process_can_proceed()) {
+		_silent = true;
+		return;
+	}
+
+	if (!_exporting && _slave) {
+		if (!follow_slave (nframes, 0)) {
+			return;
+		}
+	} 
+
+	if (_transport_speed == 0) {
+		no_roll (nframes, 0);
+		return;
+	}
+		
+	if (!_exporting) {
+		send_midi_time_code_for_cycle (nframes);
+	}
+
+	if (actively_recording()) {
+		stop_limit = max_frames;
+	} else {
+		if (Config->get_stop_at_session_end()) {
+			stop_limit = current_end_frame();
+		} else {
+			stop_limit = max_frames;
+		}
+	}
+		
+	if (maybe_stop (stop_limit)) {
+		no_roll (nframes, 0);
+		return;
+	} 
+
+	if (maybe_sync_start (nframes, offset)) {
+		return;
+	}
+
+	click (_transport_frame, nframes, offset);
+
+	prepare_diskstreams ();
+	
+	frames_moved = (long) floor (_transport_speed * nframes);
+
+	if (process_routes (nframes, offset)) {
+		no_roll (nframes, offset);
+		return;
+	}
+
+	commit_diskstreams (nframes, session_needs_butler);
+
+	if (frames_moved < 0) {
+		decrement_transport_position (-frames_moved);
+	} else {
+		increment_transport_position (frames_moved);
+	}
+
+	maybe_stop (stop_limit);
+	check_declick_out ();
+
+	if (session_needs_butler)
+		summon_butler ();
+}
+
+/** Process callback used when the auditioner is active.
+ * @param nframes number of frames to process.
+ */
+void
+Session::process_audition (nframes_t nframes)
+{
+	Event* ev;
+	boost::shared_ptr<RouteList> r = routes.reader ();
+
+	for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+		if (!(*i)->is_hidden()) {
+			(*i)->silence (nframes, 0);
+		}
+	}
+
+	/* run the auditioner, and if it says we need butler service, ask for it */
+	
+	if (auditioner->play_audition (nframes) > 0) {
+		summon_butler ();
+	} 
+
+	/* handle pending events */
+
+	while (pending_events.read (&ev, 1) == 1) {
+		merge_event (ev);
+	}
+
+	/* if we are not in the middle of a state change,
+	   and there are immediate events queued up,
+	   process them. 
+	*/
+
+	while (!non_realtime_work_pending() && !immediate_events.empty()) {
+		Event *ev = immediate_events.front ();
+		immediate_events.pop_front ();
+		process_event (ev);
+	}
+
+	if (!auditioner->active()) {
+		/* auditioner no longer active, so go back to the normal process callback */
+		process_function = &Session::process_with_events;
+	}
+}
+
+bool
+Session::maybe_sync_start (nframes_t& nframes, nframes_t& offset)
+{
+	nframes_t sync_offset;
+
+	if (!waiting_for_sync_offset) {
+		return false;
+	}
+
+	if (_engine.get_sync_offset (sync_offset) && sync_offset < nframes) {
+
+		no_roll (sync_offset, 0);
+		nframes -= sync_offset;
+		offset += sync_offset;
+		waiting_for_sync_offset = false;
+		
+		if (nframes == 0) {
+			return true; // done
+		}
+		
+	} else {
+		no_roll (nframes, 0);
+		return true; // done
+	}
+
+	return false;
+}
+