fix up fwd/reverse stuff in semitone mode

[ardour2.git] / libs / ardour / session_process.cc

/*
    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 "pbd/enumwriter.h"

#include <glibmm/thread.h>

#include "ardour/ardour.h"
#include "ardour/audioengine.h"
#include "ardour/auditioner.h"
#include "ardour/butler.h"
#include "ardour/debug.h"
#include "ardour/process_thread.h"
#include "ardour/session.h"
#include "ardour/slave.h"
#include "ardour/timestamps.h"
#include "ardour/graph.h"
#include "ardour/audio_port.h"

#include "midi++/manager.h"
#include "midi++/mmc.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 (pframes_t nframes)
{
        MIDI::Manager::instance()->cycle_start(nframes);

        _silent = false;

        if (processing_blocked()) {
                _silent = true;
                return;
        }

        if (non_realtime_work_pending()) {
                if (!_butler->transport_work_requested ()) {
                        post_transport ();
                }
        }

        _engine.main_thread()->get_buffers ();

        (this->*process_function) (nframes);

        _engine.main_thread()->drop_buffers ();

        // the ticker is for sending time information like MidiClock
        framepos_t transport_frames = transport_frame();
        Timecode::BBT_Time transport_bbt;
        bbt_time(transport_frames, transport_bbt);
        Timecode::Time transport_timecode;
        timecode_time(transport_frames, transport_timecode);
        tick (transport_frames, transport_bbt, transport_timecode); /* EMIT SIGNAL */

        SendFeedback (); /* EMIT SIGNAL */

        MIDI::Manager::instance()->cycle_end();
}

int
Session::fail_roll (pframes_t nframes)
{
        return no_roll (nframes);
}

int
Session::no_roll (pframes_t nframes)
{
        framepos_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);
        }

        if (route_graph->threads_in_use() > 0) {
                DEBUG_TRACE(DEBUG::ProcessThreads,"calling graph/no-roll\n");
                route_graph->routes_no_roll( nframes, _transport_frame, end_frame, non_realtime_work_pending(), actively_recording(), declick);
        } else {
                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, 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 (pframes_t nframes, bool& need_butler)
{
        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 framepos_t start_frame = _transport_frame;
        const framepos_t end_frame = _transport_frame + floor (nframes * _transport_speed);

        /* XXX this is hack to force use of the graph even if we are only
           using 1 thread. its needed because otherwise when we remove
           tracks, the graph never gets updated.
        */
        if (1 || route_graph->threads_in_use() > 0) {
                DEBUG_TRACE(DEBUG::ProcessThreads,"calling graph/process-routes\n");
                route_graph->process_routes( nframes, start_frame, end_frame, declick, record_active, rec_monitors, need_butler);
        } else {

                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, declick, record_active, rec_monitors, need_butler)) < 0) {
                                stop_transport ();
                                return -1;
                        }
                }
        }

        return 0;
}

int
Session::silent_process_routes (pframes_t nframes, bool& need_butler)
{
        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 framepos_t start_frame = _transport_frame;
        const framepos_t end_frame = _transport_frame + lrintf(nframes * _transport_speed);

        /* XXX this is hack to force use of the graph even if we are only
           using 1 thread. its needed because otherwise when we remove
           tracks, the graph never gets updated.
        */
        if (1 || route_graph->threads_in_use() > 0) {
                route_graph->silent_process_routes( nframes, start_frame, end_frame, record_active, rec_monitors, need_butler);
        } else {
                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, record_active, rec_monitors, need_butler)) < 0) {
                                stop_transport ();
                                return -1;
                        }
                }
        }

        return 0;
}

void
Session::get_track_statistics ()
{
        float pworst = 1.0f;
        float cworst = 1.0f;

        boost::shared_ptr<RouteList> rl = routes.reader();
        for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {

                boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);

                if (!tr || tr->hidden()) {
                        continue;
                }

                pworst = min (pworst, tr->playback_buffer_load());
                cworst = min (cworst, tr->capture_buffer_load());
        }

        g_atomic_int_set (&_playback_load, (uint32_t) floor (pworst * 100.0f));
        g_atomic_int_set (&_capture_load, (uint32_t) floor (cworst * 100.0f));

        if (actively_recording()) {
                set_dirty();
        }
}

/** Process callback used when the auditioner is not active */
void
Session::process_with_events (pframes_t nframes)
{
        SessionEvent*  ev;
        pframes_t      this_nframes;
        framepos_t     end_frame;
        bool           session_needs_butler = false;
        framepos_t     stop_limit;
        framecnt_t     frames_moved;

        /* make sure the auditioner is silent */

        if (auditioner) {
                auditioner->silence (nframes);
        }

        /* 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()) {
                SessionEvent *ev = immediate_events.front ();
                immediate_events.pop_front ();
                process_event (ev);
        }

        /* Decide on what to do with quarter-frame MTC during this cycle */

        bool const was_sending_qf_mtc = _send_qf_mtc;
        double const tolerance = Config->get_mtc_qf_speed_tolerance() / 100.0;

        if (_transport_speed != 0) {
                _send_qf_mtc = (
                        Config->get_send_mtc () &&
                        _transport_speed >= (1 - tolerance) &&
                        _transport_speed <= (1 + tolerance)
                        );

                if (_send_qf_mtc && !was_sending_qf_mtc) {
                        /* we will re-start quarter-frame MTC this cycle, so send a full update to set things up */
                        _send_timecode_update = true;
                }

                if (Config->get_send_mtc() && !_send_qf_mtc && _pframes_since_last_mtc > (frame_rate () / 4)) {
                        /* we're sending MTC, but we're not sending QF MTC at the moment, and it's been
                           a quarter of a second since we sent anything at all, so send a full MTC update
                           this cycle.
                        */
                        _send_timecode_update = true;
                }

                _pframes_since_last_mtc += nframes;
        }

        /* Events caused a transport change (or we re-started sending
         * MTC), so send an MTC Full Frame (Timecode) 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_timecode_update) {
                send_full_time_code (_transport_frame);
        }

        if (!process_can_proceed()) {
                _silent = true;
                return;
        }

        if (events.empty() || next_event == events.end()) {
                process_without_events (nframes);
                return;
        }

        if (_transport_speed == 1.0) {
                frames_moved = (framecnt_t) nframes;
        } else {
                interpolation.set_target_speed (fabs(_target_transport_speed));
                interpolation.set_speed (fabs(_transport_speed));
                frames_moved = (framecnt_t) interpolation.interpolate (0, nframes, 0, 0);
        }

        end_frame = _transport_frame + frames_moved;

        {
                SessionEvent* this_event;
                Events::iterator the_next_one;

                if (!process_can_proceed()) {
                        _silent = true;
                        return;
                }

                if (!_exporting && _slave) {
                        if (!follow_slave (nframes)) {
                                return;
                        }
                }

                if (_transport_speed == 0) {
                        no_roll (nframes);
                        return;
                }

                if (!_exporting && !timecode_transmission_suspended()) {
                        send_midi_time_code_for_cycle (_transport_frame, end_frame, nframes);
                }

                if (actively_recording()) {
                        stop_limit = max_framepos;
                } else {

                        if (Config->get_stop_at_session_end()) {
                                stop_limit = current_end_frame();
                        } else {
                                stop_limit = max_framepos;
                        }
                }

                if (maybe_stop (stop_limit)) {
                        no_roll (nframes);
                        return;
                }

                this_event = *next_event;
                the_next_one = next_event;
                ++the_next_one;

                /* 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 = (framecnt_t) 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 = (framecnt_t) (this_event->action_frame - _transport_frame);
                                this_nframes = abs (floor(frames_moved / _transport_speed));
                        }

                        if (this_nframes) {

                                click (_transport_frame, this_nframes);

                                if (process_routes (this_nframes, session_needs_butler)) {
                                        fail_roll (nframes);
                                        return;
                                }

                                get_track_statistics ();

                                nframes -= this_nframes;

                                if (frames_moved < 0) {
                                        decrement_transport_position (-frames_moved);
                                } else {
                                        increment_transport_position (frames_moved);
                                }

                                maybe_stop (stop_limit);
                                check_declick_out ();
                        }

                        _engine.split_cycle (this_nframes);

                        /* 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 (nframes && non_realtime_work_pending()) {
                                no_roll (nframes);
                                break;
                        }

                        /* this is necessary to handle the case of seamless looping */
                        end_frame = _transport_frame + floor (nframes * _transport_speed);
                }

                set_next_event ();

        } /* implicit release of route lock */

        if (session_needs_butler) {
                _butler->summon ();
        }
}

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_external_sync() || (sl && sl->ok() && sl->locked()))) {
                return true;
        }

        return false;
}

bool
Session::follow_slave (pframes_t nframes)
{
        double slave_speed;
        framepos_t slave_transport_frame;
        framecnt_t this_delta;
        int dir;

        if (!_slave->ok()) {
                stop_transport ();
                config.set_external_sync (false);
                goto noroll;
        }

        _slave->speed_and_position (slave_speed, slave_transport_frame);

        DEBUG_TRACE (DEBUG::Slave, string_compose ("Slave position %1 speed %2\n", slave_transport_frame, slave_speed));

        if (!_slave->locked()) {
                DEBUG_TRACE (DEBUG::Slave, "slave not locked\n");
                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 (_slave->starting()) {
                slave_speed = 0.0f;
        }

        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 {

                /* if we are chasing and the average delta between us and the
                   master gets too big, we want to switch to silent
                   motion. so keep track of that here.
                */

                if (_slave_state == Running) {
                        calculate_moving_average_of_slave_delta(dir, this_delta);
                }
        }

        track_slave_state (slave_speed, slave_transport_frame, this_delta);

        DEBUG_TRACE (DEBUG::Slave, string_compose ("slave state %1 @ %2 speed %3 cur delta %4 avg delta %5\n",
                                                   _slave_state, slave_transport_frame, slave_speed, this_delta, average_slave_delta));


        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
                        */

                        float delta;

                        if (average_slave_delta == 0) {
                                delta = this_delta;
                                delta *= dir;
                        } else {
                                delta = average_slave_delta;
                                delta *= average_dir;
                        }

#ifndef NDEBUG
                        if (slave_speed != 0.0) {
                                DEBUG_TRACE (DEBUG::Slave, string_compose ("delta = %1 speed = %2 ts = %3 M@%4 S@%5 avgdelta %6\n",
                                                                           (int) (dir * this_delta),
                                                                           slave_speed,
                                                                           _transport_speed,
                                                                           _transport_frame,
                                                                           slave_transport_frame,
                                                                           average_slave_delta));
                        }
#endif

                        if (_slave->give_slave_full_control_over_transport_speed()) {
                                set_transport_speed (slave_speed, false, false);
                                //std::cout << "set speed = " << slave_speed << "\n";
                        } else {
                                float adjusted_speed = slave_speed + (1.5 * (delta /  float(_current_frame_rate)));
                                request_transport_speed (adjusted_speed);
                                DEBUG_TRACE (DEBUG::Slave, string_compose ("adjust using %1 towards %2 ratio %3 current %4 slave @ %5\n",
                                                                           delta, adjusted_speed, adjusted_speed/slave_speed, _transport_speed,
                                                                           slave_speed));
                        }

#if 1
                        if ((framecnt_t) abs(average_slave_delta) > _slave->resolution()) {
                                cerr << "average slave delta greater than slave resolution (" << _slave->resolution() << "), going to silent motion\n";
                                goto silent_motion;
                        }
#endif
                }
        }


        if (_slave_state == Running && !non_realtime_work_pending()) {
                /* speed is set, we're locked, and good to go */
                return true;
        }

  silent_motion:
        DEBUG_TRACE (DEBUG::Slave, "silent motion\n")
        follow_slave_silently (nframes, slave_speed);

  noroll:
        /* don't move at all */
        DEBUG_TRACE (DEBUG::Slave, "no roll\n")
        no_roll (nframes);
        return false;
}

void
Session::calculate_moving_average_of_slave_delta (int dir, framecnt_t this_delta)
{
        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++] = (framecnt_t) dir *  (framecnt_t) this_delta;
        }

        if (have_first_delta_accumulator) {
                average_slave_delta = 0L;
                for (int i = 0; i < delta_accumulator_size; ++i) {
                        average_slave_delta += delta_accumulator[i];
                }
                average_slave_delta /= (int32_t) delta_accumulator_size;
                if (average_slave_delta < 0L) {
                        average_dir = -1;
                        average_slave_delta = abs(average_slave_delta);
                } else {
                        average_dir = 1;
                }
        }
}

void
Session::track_slave_state (float slave_speed, framepos_t slave_transport_frame, framecnt_t this_delta)
{
        if (slave_speed != 0.0f) {

                /* slave is running */

                switch (_slave_state) {
                case Stopped:
                        if (_slave->requires_seekahead()) {
                                slave_wait_end = slave_transport_frame + _slave->seekahead_distance ();
                                DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, but running, requires seekahead to %1\n", slave_wait_end));
                                /* we can call locate() here because we are in process context */
                                locate (slave_wait_end, false, false);
                                _slave_state = Waiting;

                        } 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:
                default:
                        break;
                }

                if (_slave_state == Waiting) {

                        DEBUG_TRACE (DEBUG::Slave, string_compose ("slave waiting at %1\n", slave_transport_frame));

                        if (slave_transport_frame >= slave_wait_end) {

                                DEBUG_TRACE (DEBUG::Slave, string_compose ("slave start at %1 vs %2\n", slave_transport_frame, _transport_frame));

                                _slave_state = Running;

                                /* now perform a "micro-seek" within the disk buffers to realign ourselves
                                   precisely with the master.
                                */


                                bool ok = true;
                                framecnt_t frame_delta = slave_transport_frame - _transport_frame;

                                boost::shared_ptr<RouteList> rl = routes.reader();
                                for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
                                        boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
                                        if (tr && !tr->can_internal_playback_seek (frame_delta)) {
                                                ok = false;
                                                break;
                                        }
                                }

                                if (ok) {
                                        for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
                                                boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
                                                if (tr) {
                                                        tr->internal_playback_seek (frame_delta);
                                                }
                                        }
                                        _transport_frame += frame_delta;

                                } else {
                                        cerr << "cannot micro-seek\n";
                                        /* XXX what? */
                                }

                                memset (delta_accumulator, 0, sizeof (int32_t) * delta_accumulator_size);
                                average_slave_delta = 0L;
                                this_delta = 0;
                        }
                }

                if (_slave_state == Running && _transport_speed == 0.0f) {
                        DEBUG_TRACE (DEBUG::Slave, "slave starts transport\n");
                        start_transport ();
                }

        } else { // slave_speed is 0

                /* slave has stopped */

                if (_transport_speed != 0.0f) {
                        DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stops transport: %1 frame %2 tf %3\n", slave_speed, slave_transport_frame, _transport_frame));
                        stop_transport ();
                }

                if (slave_transport_frame != _transport_frame) {
                        DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, move to %1\n", slave_transport_frame));
                        force_locate (slave_transport_frame, false);
                }

                _slave_state = Stopped;
        }
}

void
Session::follow_slave_silently (pframes_t nframes, float slave_speed)
{
        if (slave_speed && _transport_speed) {

                /* something isn't right, but we should move with the master
                   for now.
                */

                bool need_butler;

                silent_process_routes (nframes, need_butler);

                get_track_statistics ();

                if (need_butler) {
                        _butler->summon ();
                }

                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);
                }

                framepos_t stop_limit;

                if (actively_recording()) {
                        stop_limit = max_framepos;
                } else {
                        if (Config->get_stop_at_session_end()) {
                                stop_limit = current_end_frame();
                        } else {
                                stop_limit = max_framepos;
                        }
                }

                maybe_stop (stop_limit);
        }
}

void
Session::process_without_events (pframes_t nframes)
{
        bool session_needs_butler = false;
        framepos_t stop_limit;
        framecnt_t frames_moved;

        if (!process_can_proceed()) {
                _silent = true;
                return;
        }

        if (!_exporting && _slave) {
                if (!follow_slave (nframes)) {
                        return;
                }
        }

        if (_transport_speed == 0) {
                fail_roll (nframes);
                return;
        }

        if (_transport_speed == 1.0) {
                frames_moved = (framecnt_t) nframes;
        } else {
                interpolation.set_target_speed (fabs(_target_transport_speed));
                interpolation.set_speed (fabs(_transport_speed));
                frames_moved = (framecnt_t) interpolation.interpolate (0, nframes, 0, 0);
        }

        if (!_exporting && !timecode_transmission_suspended()) {
                send_midi_time_code_for_cycle (_transport_frame, _transport_frame + frames_moved, nframes);
        }

        if (actively_recording()) {
                stop_limit = max_framepos;
        } else {
                if (Config->get_stop_at_session_end()) {
                        stop_limit = current_end_frame();
                } else {
                        stop_limit = max_framepos;
                }
        }

        if (maybe_stop (stop_limit)) {
                fail_roll (nframes);
                return;
        }

        if (maybe_sync_start (nframes)) {
                return;
        }

        click (_transport_frame, nframes);

        if (process_routes (nframes, session_needs_butler)) {
                fail_roll (nframes);
                return;
        }

        get_track_statistics ();

        /* XXX: I'm not sure whether this is correct, but at least it
           matches process_with_events, so that this new frames_moved
           is -ve when transport speed is -ve.  This means that the
           transport position is updated correctly when we are in
           reverse.  It seems a bit wrong that we're not using the
           interpolator to compute this.
        */

        frames_moved = (framecnt_t) floor (_transport_speed * nframes);

        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) {
                _butler->summon ();
        }
}

/** Process callback used when the auditioner is active.
 * @param nframes number of frames to process.
 */
void
Session::process_audition (pframes_t nframes)
{
        SessionEvent* 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);
                }
        }

        /* run the auditioner, and if it says we need butler service, ask for it */

        if (auditioner->play_audition (nframes) > 0) {
                _butler->summon ();
        }

        /* if using a monitor section, run it because otherwise we don't hear anything */

        if (auditioner->needs_monitor()) {
                _monitor_out->passthru (_transport_frame, _transport_frame + nframes, nframes, false);
        }

        /* 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()) {
                SessionEvent *ev = immediate_events.front ();
                immediate_events.pop_front ();
                process_event (ev);
        }

        if (!auditioner->auditioning()) {
                /* auditioner no longer active, so go back to the normal process callback */
                process_function = &Session::process_with_events;
        }
}

bool
Session::maybe_sync_start (pframes_t & nframes)
{
        pframes_t sync_offset;

        if (!waiting_for_sync_offset) {
                return false;
        }

        if (_engine.get_sync_offset (sync_offset) && sync_offset < nframes) {

                /* generate silence up to the sync point, then
                   adjust nframes + offset to reflect whatever
                   is left to do.
                */

                no_roll (sync_offset);
                nframes -= sync_offset;
                Port::increment_global_port_buffer_offset (sync_offset);
                waiting_for_sync_offset = false;

                if (nframes == 0) {
                        return true; // done, nothing left to process
                }

        } else {

                /* sync offset point is not within this process()
                   cycle, so just generate silence. and don't bother
                   with any fancy stuff here, just the minimal silence.
                */

                _silent = true;

                if (Config->get_locate_while_waiting_for_sync()) {
                        if (micro_locate (nframes)) {
                                /* XXX ERROR !!! XXX */
                        }
                }

                return true; // done, nothing left to process
        }

        return false;
}

void
Session::queue_event (SessionEvent* ev)
{
        if (_state_of_the_state & Deletion) {
                return;
        } else if (_state_of_the_state & Loading) {
                merge_event (ev);
        } else {
                pending_events.write (&ev, 1);
        }
}

void
Session::set_next_event ()
{
        if (events.empty()) {
                next_event = events.end();
                return;
        }

        if (next_event == events.end()) {
                next_event = events.begin();
        }

        if ((*next_event)->action_frame > _transport_frame) {
                next_event = events.begin();
        }

        for (; next_event != events.end(); ++next_event) {
                if ((*next_event)->action_frame >= _transport_frame) {
                        break;
                }
        }
}

void
Session::process_event (SessionEvent* ev)
{
        bool remove = true;
        bool del = true;

        /* if we're in the middle of a state change (i.e. waiting
           for the butler thread to complete the non-realtime
           part of the change), we'll just have to queue this
           event for a time when the change is complete.
        */

        if (non_realtime_work_pending()) {

                /* except locates, which we have the capability to handle */

                if (ev->type != SessionEvent::Locate) {
                        immediate_events.insert (immediate_events.end(), ev);
                        _remove_event (ev);
                        return;
                }
        }

        DEBUG_TRACE (DEBUG::SessionEvents, string_compose ("Processing event: %1 @ %2\n", enum_2_string (ev->type), _transport_frame));

        switch (ev->type) {
        case SessionEvent::SetLoop:
                set_play_loop (ev->yes_or_no);
                break;

        case SessionEvent::AutoLoop:
                if (play_loop) {
                        start_locate (ev->target_frame, true, false, Config->get_seamless_loop());
                }
                remove = false;
                del = false;
                break;

        case SessionEvent::Locate:
                if (ev->yes_or_no) {
                        // cerr << "forced locate to " << ev->target_frame << endl;
                        locate (ev->target_frame, false, true, false);
                } else {
                        // cerr << "soft locate to " << ev->target_frame << endl;
                        start_locate (ev->target_frame, false, true, false);
                }
                _send_timecode_update = true;
                break;

        case SessionEvent::LocateRoll:
                if (ev->yes_or_no) {
                        // cerr << "forced locate to+roll " << ev->target_frame << endl;
                        locate (ev->target_frame, true, true, false);
                } else {
                        // cerr << "soft locate to+roll " << ev->target_frame << endl;
                        start_locate (ev->target_frame, true, true, false);
                }
                _send_timecode_update = true;
                break;

        case SessionEvent::LocateRollLocate:
                // locate is handled by ::request_roll_at_and_return()
                _requested_return_frame = ev->target_frame;
                request_locate (ev->target2_frame, true);
                break;


        case SessionEvent::SetTransportSpeed:
                set_transport_speed (ev->speed, ev->yes_or_no, ev->second_yes_or_no);
                break;

        case SessionEvent::PunchIn:
                // cerr << "PunchIN at " << transport_frame() << endl;
                if (config.get_punch_in() && record_status() == Enabled) {
                        enable_record ();
                }
                remove = false;
                del = false;
                break;

        case SessionEvent::PunchOut:
                // cerr << "PunchOUT at " << transport_frame() << endl;
                if (config.get_punch_out()) {
                        step_back_from_record ();
                }
                remove = false;
                del = false;
                break;

        case SessionEvent::StopOnce:
                if (!non_realtime_work_pending()) {
                        stop_transport (ev->yes_or_no);
                        _clear_event_type (SessionEvent::StopOnce);
                }
                remove = false;
                del = false;
                break;

        case SessionEvent::RangeStop:
                if (!non_realtime_work_pending()) {
                        stop_transport (ev->yes_or_no);
                }
                remove = false;
                del = false;
                break;

        case SessionEvent::RangeLocate:
                start_locate (ev->target_frame, true, true, false);
                remove = false;
                del = false;
                break;

        case SessionEvent::Overwrite:
                overwrite_some_buffers (static_cast<Track*>(ev->ptr));
                break;

        case SessionEvent::SetTrackSpeed:
                set_track_speed (static_cast<Track*> (ev->ptr), ev->speed);
                break;

        case SessionEvent::SetSyncSource:
                use_sync_source (ev->slave);
                break;

        case SessionEvent::Audition:
                set_audition (ev->region);
                // drop reference to region
                ev->region.reset ();
                break;

        case SessionEvent::InputConfigurationChange:
                add_post_transport_work (PostTransportInputChange);
                _butler->schedule_transport_work ();
                break;

        case SessionEvent::SetPlayAudioRange:
                set_play_range (ev->audio_range, (ev->speed == 1.0f));
                break;

        case SessionEvent::RealTimeOperation:
                process_rtop (ev);
                del = false; // other side of RT request needs to clean up
                break;

        case SessionEvent::AdjustPlaybackBuffering:
                schedule_playback_buffering_adjustment ();
                break;

        case SessionEvent::AdjustCaptureBuffering:
                schedule_capture_buffering_adjustment ();
                break;

        case SessionEvent::SetTimecodeTransmission:
                g_atomic_int_set (&_suspend_timecode_transmission, ev->yes_or_no ? 0 : 1);
                break;

        default:
          fatal << string_compose(_("Programming error: illegal event type in process_event (%1)"), ev->type) << endmsg;
                /*NOTREACHED*/
                break;
        };

        if (remove) {
                del = del && !_remove_event (ev);
        }

        if (del) {
                delete ev;
        }
}