Tempo ramps -update audio-locked meter bbt correctly, a bit more explanation.
[ardour.git] / libs / ardour / tempo.cc
index a9247f60fd89b760223caac01ce28982896b790e..45c26b8c361015ce657e607bf5f23a8e25f55f13 100644 (file)
@@ -73,7 +73,10 @@ Meter::frames_per_bar (const Tempo& tempo, framecnt_t sr) const
 const string TempoSection::xml_state_node_name = "Tempo";
 
 TempoSection::TempoSection (const XMLNode& node)
-       : MetricSection (0.0), Tempo (TempoMap::default_tempo())
+       : MetricSection (0.0)
+       , Tempo (TempoMap::default_tempo())
+       , _c_func (0.0)
+       , _active (true)
 {
        const XMLProperty *prop;
        LocaleGuard lg;
@@ -138,13 +141,11 @@ TempoSection::TempoSection (const XMLNode& node)
 
        set_movable (string_is_affirmative (prop->value()));
 
-       if ((prop = node.property ("bar-offset")) == 0) {
-               _bar_offset = -1.0;
+       if ((prop = node.property ("active")) == 0) {
+               warning << _("TempoSection XML node has no \"active\" property") << endmsg;
+               set_active(true);
        } else {
-               if (sscanf (prop->value().c_str(), "%lf", &_bar_offset) != 1 || _bar_offset < 0.0) {
-                       error << _("TempoSection XML node has an illegal \"bar-offset\" value") << endmsg;
-                       throw failed_constructor();
-               }
+               set_active (string_is_affirmative (prop->value()));
        }
 
        if ((prop = node.property ("tempo-type")) == 0) {
@@ -175,26 +176,16 @@ TempoSection::get_state() const
        root->add_property ("beats-per-minute", buf);
        snprintf (buf, sizeof (buf), "%f", _note_type);
        root->add_property ("note-type", buf);
-       // snprintf (buf, sizeof (buf), "%f", _bar_offset);
-       // root->add_property ("bar-offset", buf);
        snprintf (buf, sizeof (buf), "%s", movable()?"yes":"no");
        root->add_property ("movable", buf);
+       snprintf (buf, sizeof (buf), "%s", active()?"yes":"no");
+       root->add_property ("active", buf);
        root->add_property ("tempo-type", enum_2_string (_type));
        root->add_property ("lock-style", enum_2_string (position_lock_style()));
 
        return *root;
 }
 
-void
-
-TempoSection::update_bar_offset_from_bbt (const Meter& m)
-{
-       _bar_offset = (pulse() * BBT_Time::ticks_per_beat) /
-               (m.divisions_per_bar() * BBT_Time::ticks_per_beat);
-
-       DEBUG_TRACE (DEBUG::TempoMath, string_compose ("Tempo set bar offset to %1 from %2 w/%3\n", _bar_offset, pulse(), m.divisions_per_bar()));
-}
-
 void
 TempoSection::set_type (Type type)
 {
@@ -204,7 +195,7 @@ TempoSection::set_type (Type type)
 /** returns the tempo in whole pulses per minute at the zero-based (relative to session) frame.
 */
 double
-TempoSection::tempo_at_frame (framepos_t f, framecnt_t frame_rate) const
+TempoSection::tempo_at_frame (const framepos_t& f, const framecnt_t& frame_rate) const
 {
 
        if (_type == Constant) {
@@ -220,25 +211,25 @@ TempoSection::tempo_at_frame (framepos_t f, framecnt_t frame_rate) const
    note that the tempo map may have multiple such values.
 */
 framepos_t
-TempoSection::frame_at_tempo (double bpm, double b, framecnt_t frame_rate) const
+TempoSection::frame_at_tempo (const double& ppm, const double& b, const framecnt_t& frame_rate) const
 {
        if (_type == Constant) {
-               return ((b - pulse())  * frames_per_beat (frame_rate))  + frame();
+               return ((b - pulse())  * frames_per_pulse (frame_rate))  + frame();
        }
 
-       return minute_to_frame (time_at_pulse_tempo (bpm), frame_rate) + frame();
+       return minute_to_frame (time_at_pulse_tempo (ppm), frame_rate) + frame();
 }
 /** returns the tempo in pulses per minute at the zero-based (relative to session) beat.
 */
 double
-TempoSection::tempo_at_pulse (double b) const
+TempoSection::tempo_at_pulse (const double& p) const
 {
 
        if (_type == Constant) {
                return pulses_per_minute();
        }
-       double const bpm = pulse_tempo_at_pulse (b - pulse());
-       return bpm;
+       double const ppm = pulse_tempo_at_pulse (p - pulse());
+       return ppm;
 }
 
 /** returns the zero-based beat (relative to session)
@@ -246,14 +237,14 @@ TempoSection::tempo_at_pulse (double b) const
    note that the session tempo map may have multiple beats at a given tempo.
 */
 double
-TempoSection::pulse_at_tempo (double bpm, framepos_t f, framecnt_t frame_rate) const
+TempoSection::pulse_at_tempo (const double& ppm, const framepos_t& f, const framecnt_t& frame_rate) const
 {
        if (_type == Constant) {
-               double const beats = ((f - frame()) / frames_per_beat (frame_rate)) + pulse();
+               double const beats = ((f - frame()) / frames_per_pulse (frame_rate)) + pulse();
                return  beats;
        }
 
-       return pulse_at_pulse_tempo (bpm) + pulse();
+       return pulse_at_pulse_tempo (ppm) + pulse();
 }
 
 /** returns the zero-based pulse (relative to session origin)
@@ -261,10 +252,10 @@ TempoSection::pulse_at_tempo (double bpm, framepos_t f, framecnt_t frame_rate) c
    lies.
 */
 double
-TempoSection::pulse_at_frame (framepos_t f, framecnt_t frame_rate) const
+TempoSection::pulse_at_frame (const framepos_t& f, const framecnt_t& frame_rate) const
 {
        if (_type == Constant) {
-               return ((f - frame()) / frames_per_beat (frame_rate)) + pulse();
+               return ((f - frame()) / frames_per_pulse (frame_rate)) + pulse();
        }
 
        return pulse_at_time (frame_to_minute (f - frame(), frame_rate)) + pulse();
@@ -276,13 +267,13 @@ TempoSection::pulse_at_frame (framepos_t f, framecnt_t frame_rate) const
 */
 
 framepos_t
-TempoSection::frame_at_pulse (double b, framecnt_t frame_rate) const
+TempoSection::frame_at_pulse (const double& p, const framecnt_t& frame_rate) const
 {
        if (_type == Constant) {
-               return (framepos_t) floor ((b - pulse()) * frames_per_beat (frame_rate)) + frame();
+               return (framepos_t) floor ((p - pulse()) * frames_per_pulse (frame_rate)) + frame();
        }
 
-       return minute_to_frame (time_at_pulse (b - pulse()), frame_rate) + frame();
+       return minute_to_frame (time_at_pulse (p - pulse()), frame_rate) + frame();
 }
 
 /*
@@ -358,27 +349,27 @@ https://www.zhdk.ch/fileadmin/data_subsites/data_icst/Downloads/Timegrid/ICST_Te
   and duration (pulses into global start) of some later tempo section.
 */
 double
-TempoSection::compute_c_func_pulse (double end_bpm, double end_pulse, framecnt_t frame_rate)
+TempoSection::compute_c_func_pulse (const double& end_bpm, const double& end_pulse, const framecnt_t& frame_rate)
 {
        double const log_tempo_ratio = log (end_bpm / pulses_per_minute());
-       return pulses_per_minute() *  (exp (log_tempo_ratio) - 1) / (end_pulse - pulse());
+       return pulses_per_minute() *  (expm1 (log_tempo_ratio)) / (end_pulse - pulse());
 }
 
 /* compute the function constant from some later tempo section, given tempo (whole pulses/min.) and distance (in frames) from session origin */
 double
-TempoSection::compute_c_func_frame (double end_bpm, framepos_t end_frame, framecnt_t frame_rate) const
+TempoSection::compute_c_func_frame (const double& end_bpm, const framepos_t& end_frame, const framecnt_t& frame_rate) const
 {
        return c_func (end_bpm, frame_to_minute (end_frame - frame(), frame_rate));
 }
 
 framecnt_t
-TempoSection::minute_to_frame (double time, framecnt_t frame_rate) const
+TempoSection::minute_to_frame (const double& time, const framecnt_t& frame_rate) const
 {
        return (framecnt_t) floor ((time * 60.0 * frame_rate) + 0.5);
 }
 
 double
-TempoSection::frame_to_minute (framecnt_t frame, framecnt_t frame_rate) const
+TempoSection::frame_to_minute (const framecnt_t& frame, const framecnt_t& frame_rate) const
 {
        return (frame / (double) frame_rate) / 60.0;
 }
@@ -399,66 +390,44 @@ TempoSection::c_func (double end_bpm, double end_time) const
 
 /* tempo in ppm at time in minutes */
 double
-TempoSection::pulse_tempo_at_time (double time) const
+TempoSection::pulse_tempo_at_time (const double& time) const
 {
        return exp (_c_func * time) * pulses_per_minute();
 }
 
 /* time in minutes at tempo in ppm */
 double
-TempoSection::time_at_pulse_tempo (double pulse_tempo) const
+TempoSection::time_at_pulse_tempo (const double& pulse_tempo) const
 {
        return log (pulse_tempo / pulses_per_minute()) / _c_func;
 }
 
 /* tick at tempo in ppm */
 double
-TempoSection::pulse_at_pulse_tempo (double pulse_tempo) const
+TempoSection::pulse_at_pulse_tempo (const double& pulse_tempo) const
 {
        return (pulse_tempo - pulses_per_minute()) / _c_func;
 }
 
 /* tempo in ppm at tick */
 double
-TempoSection::pulse_tempo_at_pulse (double pulse) const
+TempoSection::pulse_tempo_at_pulse (const double& pulse) const
 {
        return (pulse * _c_func) + pulses_per_minute();
 }
 
 /* pulse at time in minutes */
 double
-TempoSection::pulse_at_time (double time) const
+TempoSection::pulse_at_time (const double& time) const
 {
-       return ((exp (_c_func * time)) - 1) * (pulses_per_minute() / _c_func);
+       return expm1 (_c_func * time) * (pulses_per_minute() / _c_func);
 }
 
 /* time in minutes at pulse */
 double
-TempoSection::time_at_pulse (double pulse) const
+TempoSection::time_at_pulse (const double& pulse) const
 {
-       return log (((_c_func * pulse) / pulses_per_minute()) + 1) / _c_func;
-}
-
-
-void
-TempoSection::update_bbt_time_from_bar_offset (const Meter& meter)
-{
-       double new_beat;
-
-       if (_bar_offset < 0.0) {
-               /* not set yet */
-               return;
-       }
-
-       new_beat = pulse();
-
-       double ticks = BBT_Time::ticks_per_beat * meter.divisions_per_bar() * _bar_offset;
-       new_beat = ticks / BBT_Time::ticks_per_beat;
-
-       DEBUG_TRACE (DEBUG::TempoMath, string_compose ("from bar offset %1 and dpb %2, ticks = %3->%4 beats = %5\n",
-                                                      _bar_offset, meter.divisions_per_bar(), ticks, new_beat, new_beat));
-
-       set_pulse (new_beat);
+       return log1p ((_c_func * pulse) / pulses_per_minute()) / _c_func;
 }
 
 /***********************************************************************/
@@ -474,6 +443,7 @@ MeterSection::MeterSection (const XMLNode& node)
        const XMLProperty *prop;
        BBT_Time bbt;
        double pulse = 0.0;
+       double beat = 0.0;
        framepos_t frame = 0;
        pair<double, BBT_Time> start;
 
@@ -496,8 +466,15 @@ MeterSection::MeterSection (const XMLNode& node)
                        error << _("MeterSection XML node has an illegal \"pulse\" value") << endmsg;
                }
        }
+       set_pulse (pulse);
+
+       if ((prop = node.property ("beat")) != 0) {
+               if (sscanf (prop->value().c_str(), "%lf", &beat) != 1) {
+                       error << _("MeterSection XML node has an illegal \"beat\" vlue") << endmsg;
+               }
+       }
 
-       start.first = pulse;
+       start.first = beat;
 
        if ((prop = node.property ("bbt")) == 0) {
                error << _("MeterSection XML node has no \"bbt\" property") << endmsg;
@@ -510,7 +487,7 @@ MeterSection::MeterSection (const XMLNode& node)
        }
 
        start.second = bbt;
-       set_pulse (start);
+       set_beat (start);
 
        if ((prop = node.property ("frame")) != 0) {
                if (sscanf (prop->value().c_str(), "%li", &frame) != 1) {
@@ -564,13 +541,15 @@ MeterSection::get_state() const
        char buf[256];
        LocaleGuard lg;
 
+       snprintf (buf, sizeof (buf), "%lf", pulse());
+       root->add_property ("pulse", buf);
        snprintf (buf, sizeof (buf), "%" PRIu32 "|%" PRIu32 "|%" PRIu32,
                  bbt().bars,
                  bbt().beats,
                  bbt().ticks);
        root->add_property ("bbt", buf);
-       snprintf (buf, sizeof (buf), "%lf", pulse());
-       root->add_property ("pulse", buf);
+       snprintf (buf, sizeof (buf), "%lf", beat());
+       root->add_property ("beat", buf);
        snprintf (buf, sizeof (buf), "%f", _note_type);
        root->add_property ("note-type", buf);
        snprintf (buf, sizeof (buf), "%li", frame());
@@ -585,7 +564,41 @@ MeterSection::get_state() const
 }
 
 /***********************************************************************/
+/*
+  Tempo Map Overview
+
+  Tempos can be thought of as a source of the musical pulse.
+
+  Note that Tempo::beats_per_minute() has nothing to do with musical beats.
+  It should rather be thought of as tempo note divisions per minute.
+
+  TempoSections, which are nice to think of in whole pulses per minute,
+  and MeterSecions which divide tempo pulses into measures (via divisions_per_bar)
+  and beats (via note_divisor) are used to form a tempo map.
+  TempoSections and MeterSections may be locked to either audio or music (position lock style).
+  We construct the tempo map by first using the frame or pulse position (depending on position lock style) of each tempo.
+  We then use this pulse/frame layout to find the beat & pulse or frame position of each meter (again depending on lock style).
+
+  Having done this, we can now find any one of tempo, beat, frame or pulse if a beat, frame, pulse or tempo is known.
+
+  The first tempo and first meter are special. they must move together, and must be locked to audio.
+  Audio locked tempos which lie before the first meter are made inactive.
+  They will be re-activated if the first meter is again placed before them.
+
+  Both tempos and meters have a pulse position and a frame position.
+  Meters also have a beat position, which is always 0.0 for the first meter.
+
+  A tempo locked to music is locked to musical pulses.
+  A meter locked to music is locked to beats.
 
+  Recomputing the tempo map is the process where the 'missing' position
+  (tempo pulse or meter pulse & beat in the case of AudioTime, frame for MusicTime) is calculated.
+
+  It is important to keep the _metrics in an order that makes sense.
+  Because ramped MusicTime and AudioTime tempos can interact with each other,
+  reordering is frequent. Care must be taken to keep _metrics in a solved state.
+  Solved means ordered by frame or pulse with frame-accurate precision (see check_solved()).
+*/
 struct MetricSectionSorter {
     bool operator() (const MetricSection* a, const MetricSection* b) {
            return a->pulse() < b->pulse();
@@ -604,7 +617,7 @@ TempoMap::TempoMap (framecnt_t fr)
        BBT_Time start (1, 1, 0);
 
        TempoSection *t = new TempoSection (0.0, _default_tempo.beats_per_minute(), _default_tempo.note_type(), TempoSection::Constant);
-       MeterSection *m = new MeterSection (0.0, start, _default_meter.divisions_per_bar(), _default_meter.note_divisor());
+       MeterSection *m = new MeterSection (0.0, 0.0, start, _default_meter.divisions_per_bar(), _default_meter.note_divisor());
 
        t->set_movable (false);
        m->set_movable (false);
@@ -715,7 +728,7 @@ TempoMap::do_insert (MetricSection* section)
                        corrected.first = bbt_to_beats_locked (_metrics, corrected.second);
                        warning << string_compose (_("Meter changes can only be positioned on the first beat of a bar. Moving from %1 to %2"),
                                                   m->bbt(), corrected.second) << endmsg;
-                       m->set_pulse (corrected);
+                       //m->set_pulse (corrected);
                }
        }
 
@@ -747,6 +760,7 @@ TempoMap::do_insert (MetricSection* section)
                                         */
 
                                        *(dynamic_cast<Tempo*>(*i)) = *(dynamic_cast<Tempo*>(insert_tempo));
+                                       (*i)->set_position_lock_style (AudioTime);
                                        need_add = false;
                                } else {
                                        _metrics.erase (i);
@@ -770,6 +784,7 @@ TempoMap::do_insert (MetricSection* section)
                                         */
 
                                        *(dynamic_cast<Meter*>(*i)) = *(dynamic_cast<Meter*>(insert_meter));
+                                       (*i)->set_position_lock_style (insert_meter->position_lock_style());
                                        need_add = false;
                                } else {
                                        _metrics.erase (i);
@@ -821,14 +836,14 @@ TempoMap::do_insert (MetricSection* section)
 }
 
 void
-TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const double& where, TempoSection::Type type)
+TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const double& pulse, TempoSection::Type type)
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
                TempoSection& first (first_tempo());
                if (ts.pulse() != first.pulse()) {
                        remove_tempo_locked (ts);
-                       add_tempo_locked (tempo, where, true, type);
+                       add_tempo_locked (tempo, pulse, true, type);
                } else {
                        first.set_type (type);
                        {
@@ -853,6 +868,8 @@ TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const frame
                        add_tempo_locked (tempo, frame, true, type);
                } else {
                        first.set_type (type);
+                       first.set_pulse (0.0);
+                       first.set_position_lock_style (AudioTime);
                        {
                                /* cannot move the first tempo section */
                                *static_cast<Tempo*>(&first) = tempo;
@@ -860,22 +877,23 @@ TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const frame
                        }
                }
        }
+
        PropertyChanged (PropertyChange ());
 }
 
 void
-TempoMap::add_tempo (const Tempo& tempo, double where, ARDOUR::TempoSection::Type type)
+TempoMap::add_tempo (const Tempo& tempo, const double& pulse, ARDOUR::TempoSection::Type type)
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               add_tempo_locked (tempo, where, true, type);
+               add_tempo_locked (tempo, pulse, true, type);
        }
 
        PropertyChanged (PropertyChange ());
 }
 
 void
-TempoMap::add_tempo (const Tempo& tempo, framepos_t frame, ARDOUR::TempoSection::Type type)
+TempoMap::add_tempo (const Tempo& tempo, const framepos_t& frame, ARDOUR::TempoSection::Type type)
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
@@ -887,9 +905,8 @@ TempoMap::add_tempo (const Tempo& tempo, framepos_t frame, ARDOUR::TempoSection:
 }
 
 void
-TempoMap::add_tempo_locked (const Tempo& tempo, double where, bool recompute, ARDOUR::TempoSection::Type type)
+TempoMap::add_tempo_locked (const Tempo& tempo, double pulse, bool recompute, ARDOUR::TempoSection::Type type)
 {
-       double pulse = pulse_at_beat (_metrics, where);
        TempoSection* ts = new TempoSection (pulse, tempo.beats_per_minute(), tempo.note_type(), type);
 
        do_insert (ts);
@@ -917,12 +934,15 @@ TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const BBT_T
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
                MeterSection& first (first_meter());
-               if (ms.pulse() != first.pulse()) {
+
+               if (ms.movable()) {
                        remove_meter_locked (ms);
                        add_meter_locked (meter, bbt_to_beats_locked (_metrics, where), where, true);
                } else {
+                       const PositionLockStyle pl = ms.position_lock_style();
                        /* cannot move the first meter section */
                        *static_cast<Meter*>(&first) = meter;
+                       first.set_position_lock_style (pl);
                        recompute_map (_metrics);
                }
        }
@@ -935,23 +955,35 @@ TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const frame
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               MeterSection& first (first_meter());
-               if (ms.pulse() != first.pulse()) {
+
+               const double beat = ms.beat();
+               const BBT_Time bbt = ms.bbt();
+               if (ms.movable()) {
                        remove_meter_locked (ms);
-                       add_meter_locked (meter, frame, true);
+                       add_meter_locked (meter, frame, beat, bbt, true);
                } else {
+                       MeterSection& first (first_meter());
+                       TempoSection& first_t (first_tempo());
                        /* cannot move the first meter section */
                        *static_cast<Meter*>(&first) = meter;
+                       first.set_position_lock_style (AudioTime);
+                       first.set_pulse (0.0);
+                       first.set_frame (frame);
+                       pair<double, BBT_Time> beat = make_pair (0.0, BBT_Time (1, 1, 0));
+                       first.set_beat (beat);
+                       first_t.set_frame (first.frame());
+                       first_t.set_pulse (0.0);
+                       first_t.set_position_lock_style (AudioTime);
+
                        recompute_map (_metrics);
                }
        }
-
        PropertyChanged (PropertyChange ());
 }
 
 
 void
-TempoMap::add_meter (const Meter& meter, double beat, BBT_Time where)
+TempoMap::add_meter (const Meter& meter, const double& beat, const BBT_Time& where)
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
@@ -969,11 +1001,11 @@ TempoMap::add_meter (const Meter& meter, double beat, BBT_Time where)
 }
 
 void
-TempoMap::add_meter (const Meter& meter, framepos_t frame)
+TempoMap::add_meter (const Meter& meter, const framepos_t& frame, const double& beat, const Timecode::BBT_Time& where)
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               add_meter_locked (meter, frame, true);
+               add_meter_locked (meter, frame, beat, where, true);
        }
 
 
@@ -1000,12 +1032,11 @@ TempoMap::add_meter_locked (const Meter& meter, double beat, BBT_Time where, boo
                where.beats = 1;
                where.bars++;
        }
-
        /* new meters *always* start on a beat. */
        where.ticks = 0;
-       double pulse = pulse_at_beat (_metrics, beat);
+       double pulse = pulse_at_beat_locked (_metrics, beat);
 
-       MeterSection* new_meter = new MeterSection (pulse, where, meter.divisions_per_bar(), meter.note_divisor());
+       MeterSection* new_meter = new MeterSection (pulse, beat, where, meter.divisions_per_bar(), meter.note_divisor());
        do_insert (new_meter);
 
        if (recompute) {
@@ -1015,13 +1046,14 @@ TempoMap::add_meter_locked (const Meter& meter, double beat, BBT_Time where, boo
 }
 
 void
-TempoMap::add_meter_locked (const Meter& meter, framepos_t frame, bool recompute)
+TempoMap::add_meter_locked (const Meter& meter, framepos_t frame, double beat, Timecode::BBT_Time where, bool recompute)
 {
 
-       MeterSection* new_meter = new MeterSection (frame, meter.divisions_per_bar(), meter.note_divisor());
-       double paf = pulse_at_frame_locked (_metrics, frame);
-       pair<double, BBT_Time> beat = make_pair (paf, beats_to_bbt_locked (_metrics, beat_at_pulse (_metrics, paf)));
-       new_meter->set_pulse (beat);
+       MeterSection* new_meter = new MeterSection (frame, beat, where, meter.divisions_per_bar(), meter.note_divisor());
+
+       double pulse = pulse_at_frame_locked (_metrics, frame);
+       new_meter->set_pulse (pulse);
+
        do_insert (new_meter);
 
        if (recompute) {
@@ -1045,11 +1077,12 @@ TempoMap::predict_tempo_frame (TempoSection* section, const Tempo& bpm, const BB
        Metrics future_map;
        framepos_t ret = 0;
        TempoSection* new_section = copy_metrics_and_point (future_map, section);
+
        double const beat = bbt_to_beats_locked (future_map, bbt);
-       if (solve_map (future_map, new_section, bpm, pulse_at_beat (future_map, beat))) {
+       if (solve_map (future_map, new_section, bpm, pulse_at_beat_locked (future_map, beat))) {
                ret = new_section->frame();
        } else {
-               ret = frame_at_beat_locked (future_map, beat);
+               ret = frame_at_beat_locked (_metrics, beat);
        }
 
        Metrics::const_iterator d = future_map.begin();
@@ -1061,7 +1094,7 @@ TempoMap::predict_tempo_frame (TempoSection* section, const Tempo& bpm, const BB
 }
 
 double
-TempoMap::predict_tempo_beat (TempoSection* section, const Tempo& bpm, const framepos_t& frame)
+TempoMap::predict_tempo_pulse (TempoSection* section, const Tempo& bpm, const framepos_t& frame)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
        Metrics future_map;
@@ -1069,9 +1102,9 @@ TempoMap::predict_tempo_beat (TempoSection* section, const Tempo& bpm, const fra
        TempoSection* new_section = copy_metrics_and_point (future_map, section);
 
        if (solve_map (future_map, new_section, bpm, frame)) {
-               ret = beat_at_pulse (future_map, new_section->pulse());
+               ret = new_section->pulse();
        } else {
-               ret = beat_at_frame_locked (future_map, frame);
+               ret = pulse_at_frame_locked (_metrics, frame);
        }
 
        Metrics::const_iterator d = future_map.begin();
@@ -1110,8 +1143,8 @@ TempoMap::gui_move_tempo_beat (TempoSection* ts,  const Tempo& bpm, const double
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
                TempoSection* new_section = copy_metrics_and_point (future_map, ts);
-               if (solve_map (future_map, new_section, bpm, pulse_at_beat (future_map, beat))) {
-                       solve_map (_metrics, ts, bpm, beat);
+               if (solve_map (future_map, new_section, bpm, pulse_at_beat_locked (future_map, beat))) {
+                       solve_map (_metrics, ts, bpm, pulse_at_beat_locked (_metrics, beat));
                }
        }
 
@@ -1140,12 +1173,41 @@ TempoMap::gui_move_meter (MeterSection* ms, const Meter& mt, const double&  beat
 {
        {
                Glib::Threads::RWLock::WriterLock lm (lock);
-               solve_map (_metrics, ms, mt, pulse_at_beat (_metrics, beat));
+               solve_map (_metrics, ms, mt, pulse_at_beat_locked (_metrics, beat));
        }
 
        MetricPositionChanged (); // Emit Signal
 }
 
+bool
+TempoMap::gui_change_tempo (TempoSection* ts,  const Tempo& bpm)
+{
+       Metrics future_map;
+       bool can_solve = false;
+       {
+               Glib::Threads::RWLock::WriterLock lm (lock);
+               TempoSection* new_section = copy_metrics_and_point (future_map, ts);
+               new_section->set_beats_per_minute (bpm.beats_per_minute());
+               recompute_tempos (future_map);
+
+               if (check_solved (future_map, true)) {
+                       ts->set_beats_per_minute (bpm.beats_per_minute());
+                       recompute_map (_metrics);
+                       can_solve = true;
+               }
+       }
+
+       Metrics::const_iterator d = future_map.begin();
+       while (d != future_map.end()) {
+               delete (*d);
+               ++d;
+       }
+       if (can_solve) {
+               MetricPositionChanged (); // Emit Signal
+       }
+       return can_solve;
+}
+
 TempoSection*
 TempoMap::copy_metrics_and_point (Metrics& copy, TempoSection* section)
 {
@@ -1161,25 +1223,33 @@ TempoMap::copy_metrics_and_point (Metrics& copy, TempoSection* section)
                                } else {
                                        ret = new TempoSection (t->frame(), t->beats_per_minute(), t->note_type(), t->type());
                                }
+                               ret->set_active (t->active());
+                               ret->set_movable (t->movable());
                                copy.push_back (ret);
                                continue;
                        }
+                       TempoSection* cp = 0;
                        if (t->position_lock_style() == MusicTime) {
-                               copy.push_back (new TempoSection (t->pulse(), t->beats_per_minute(), t->note_type(), t->type()));
+                               cp = new TempoSection (t->pulse(), t->beats_per_minute(), t->note_type(), t->type());
                        } else {
-                               copy.push_back (new TempoSection (t->frame(), t->beats_per_minute(), t->note_type(), t->type()));
+                               cp = new TempoSection (t->frame(), t->beats_per_minute(), t->note_type(), t->type());
                        }
+                       cp->set_active (t->active());
+                       cp->set_movable (t->movable());
+                       copy.push_back (cp);
                }
                if ((m = dynamic_cast<MeterSection *> (*i)) != 0) {
+                       MeterSection* cp = 0;
                        if (m->position_lock_style() == MusicTime) {
-                               copy.push_back (new MeterSection (m->pulse(), m->bbt(), m->divisions_per_bar(), m->note_divisor()));
+                               cp = new MeterSection (m->pulse(), m->beat(), m->bbt(), m->divisions_per_bar(), m->note_divisor());
                        } else {
-                               copy.push_back (new MeterSection (m->frame(), m->bbt(), m->divisions_per_bar(), m->note_divisor()));
-
+                               cp = new MeterSection (m->frame(), m->beat(), m->bbt(), m->divisions_per_bar(), m->note_divisor());
                        }
+                       cp->set_movable (m->movable());
+                       copy.push_back (cp);
                }
        }
-       recompute_map (copy);
+       //recompute_map (copy);
        return ret;
 }
 
@@ -1195,7 +1265,7 @@ TempoMap::can_solve_bbt (TempoSection* ts,  const Tempo& bpm, const BBT_Time& bb
        }
 
        double const beat = bbt_to_beats_locked (copy, bbt);
-       bool ret = solve_map (copy, new_section, bpm, beat);
+       bool ret = solve_map (copy, new_section, bpm, pulse_at_beat_locked (copy, beat));
 
        Metrics::const_iterator d = copy.begin();
        while (d != copy.end()) {
@@ -1214,6 +1284,9 @@ TempoMap::change_initial_tempo (double beats_per_minute, double note_type)
 
        for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        {
                                Glib::Threads::RWLock::WriterLock lm (lock);
                                *((Tempo*) t) = newtempo;
@@ -1246,6 +1319,9 @@ TempoMap::change_existing_tempo_at (framepos_t where, double beats_per_minute, d
                TempoSection* t;
 
                if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (!first) {
                                first = t;
                        }
@@ -1285,7 +1361,7 @@ TempoMap::first_meter () const
                }
        }
 
-       fatal << _("programming error: no tempo section in tempo map!") << endmsg;
+       fatal << _("programming error: no meter section in tempo map!") << endmsg;
        abort(); /*NOTREACHED*/
        return *m;
 }
@@ -1317,7 +1393,12 @@ TempoMap::first_tempo () const
 
        for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
                if ((t = dynamic_cast<const TempoSection *> (*i)) != 0) {
-                       return *t;
+                       if (!t->active()) {
+                               continue;
+                       }
+                       if (!t->movable()) {
+                               return *t;
+                       }
                }
        }
 
@@ -1333,7 +1414,12 @@ TempoMap::first_tempo ()
 
        for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
                if ((t = dynamic_cast<TempoSection *> (*i)) != 0) {
-                       return *t;
+                       if (!t->active()) {
+                               continue;
+                       }
+                       if (!t->movable()) {
+                               return *t;
+                       }
                }
        }
 
@@ -1350,6 +1436,9 @@ TempoMap::recompute_tempos (Metrics& metrics)
                TempoSection* t;
 
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (prev_ts) {
                                if (t->position_lock_style() == AudioTime) {
                                        prev_ts->set_c_func (prev_ts->compute_c_func_frame (t->pulses_per_minute(), t->frame(), _frame_rate));
@@ -1364,6 +1453,7 @@ TempoMap::recompute_tempos (Metrics& metrics)
                        prev_ts = t;
                }
        }
+       prev_ts->set_c_func (0.0);
 }
 
 /* tempos must be positioned correctly */
@@ -1372,23 +1462,40 @@ TempoMap::recompute_meters (Metrics& metrics)
 {
        MeterSection* meter = 0;
        MeterSection* prev_m = 0;
-       double accumulated_beats = 0.0;
+       uint32_t accumulated_bars = 0;
 
        for (Metrics::const_iterator mi = metrics.begin(); mi != metrics.end(); ++mi) {
                if ((meter = dynamic_cast<MeterSection*> (*mi)) != 0) {
                        if (prev_m) {
-                               accumulated_beats += (meter->pulse() - prev_m->pulse()) * prev_m->note_divisor();
+                               const double beats_in_m = (meter->pulse() - prev_m->pulse()) * prev_m->note_divisor();
+                               accumulated_bars += (beats_in_m + 1) / prev_m->divisions_per_bar();
                        }
                        if (meter->position_lock_style() == AudioTime) {
-                               pair<double, BBT_Time> pr;
-                               pr.first = ceil (pulse_at_frame_locked (metrics, meter->frame()));
-                               BBT_Time const where = beats_to_bbt_locked (metrics, accumulated_beats);
-                               pr.second = where;
-                               meter->set_pulse (pr);
+                               double pulse = 0.0;
+                               pair<double, BBT_Time> b_bbt;
+                               if (prev_m) {
+                                       double beats = ((pulse_at_frame_locked (metrics, meter->frame()) - prev_m->pulse()) * prev_m->note_divisor()) - prev_m->beat();
+                                       b_bbt = make_pair (ceil (beats), BBT_Time (accumulated_bars + 1, 1, 0));
+                                       const double true_pulse = prev_m->pulse() + (ceil (beats) - prev_m->beat()) / prev_m->note_divisor();
+                                       const double pulse_off = true_pulse - ((beats - prev_m->beat()) / prev_m->note_divisor());
+                                       pulse = true_pulse - pulse_off;
+                               }
+                               if (!meter->movable()) {
+                                       b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
+                               }
+                               meter->set_beat (b_bbt);
+                               meter->set_pulse (pulse);
                        } else {
-                               meter->set_frame (frame_at_pulse_locked (metrics, meter->pulse()));
+                               double pulse = 0.0;
+                               if (prev_m) {
+                                       pulse = prev_m->pulse() + (meter->beat() - prev_m->beat()) / prev_m->note_divisor();
+                               } else {
+                                       pulse = pulse_at_beat_locked (metrics, meter->beat());
+                               }
+                               meter->set_frame (frame_at_pulse_locked (metrics, pulse));
+                               meter->set_pulse (pulse);
                        }
-                       meter->set_beat (accumulated_beats);
+
                        prev_m = meter;
                }
        }
@@ -1421,32 +1528,42 @@ TempoMap::recompute_map (Metrics& metrics, framepos_t end)
 }
 
 double
-TempoMap::pulse_at_beat (const Metrics& metrics, const double& beat) const
+TempoMap::pulse_at_beat (const double& beat) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return pulse_at_beat_locked (_metrics, beat);
+}
+
+double
+TempoMap::pulse_at_beat_locked (const Metrics& metrics, const double& beat) const
 {
        MeterSection* prev_ms = 0;
        double accumulated_beats = 0.0;
-       double beats_to_m = 0.0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (prev_ms) {
-                               beats_to_m = (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
-                               if (accumulated_beats + beats_to_m > beat) {
-                                       break;
-                               }
-                               accumulated_beats += (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
+                       if (prev_ms && m->beat() > beat) {
+                               break;
                        }
+                       accumulated_beats = m->beat();
                        prev_ms = m;
                }
 
        }
+       double const ret = prev_ms->pulse() + ((beat - accumulated_beats) / prev_ms->note_divisor());
+       return ret;
+}
 
-       return prev_ms->pulse() + ((beat - accumulated_beats) / prev_ms->note_divisor());
+double
+TempoMap::beat_at_pulse (const double& pulse) const
+{
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+       return beat_at_pulse_locked (_metrics, pulse);
 }
 
 double
-TempoMap::beat_at_pulse (const Metrics& metrics, const double& pulse) const
+TempoMap::beat_at_pulse_locked (const Metrics& metrics, const double& pulse) const
 {
        MeterSection* prev_ms = 0;
        double accumulated_beats = 0.0;
@@ -1454,12 +1571,10 @@ TempoMap::beat_at_pulse (const Metrics& metrics, const double& pulse) const
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (m->pulse() > pulse) {
+                       if (prev_ms && m->pulse() > pulse) {
                                break;
                        }
-                       if (prev_ms) {
-                               accumulated_beats += (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
-                       }
+                       accumulated_beats = m->beat();
                        prev_ms = m;
                }
        }
@@ -1540,14 +1655,13 @@ TempoMap::bbt_time (framepos_t frame, BBT_Time& bbt)
                return;
        }
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       frameoffset_t const frame_off = frame_offset_at (_metrics, frame);
-       double const beat = beat_at_pulse (_metrics, pulse_at_frame_locked (_metrics, frame + frame_off));
+       double const beat = beat_at_frame_locked (_metrics, frame);
 
        bbt = beats_to_bbt_locked (_metrics, beat);
 }
 
 double
-TempoMap::bbt_to_beats (Timecode::BBT_Time bbt)
+TempoMap::bbt_to_beats (const Timecode::BBT_Time& bbt)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
@@ -1571,12 +1685,10 @@ TempoMap::bbt_to_beats_locked (const Metrics& metrics, const Timecode::BBT_Time&
                        double bars_to_m = 0.0;
                        if (prev_ms) {
                                bars_to_m = (m->beat() - prev_ms->beat()) / prev_ms->divisions_per_bar();
-                       }
-                       if ((bars_to_m + accumulated_bars) > (bbt.bars - 1)) {
-                               break;
-                       }
-                       if (prev_ms) {
-                               accumulated_beats += m->beat() - prev_ms->beat();
+                               if ((bars_to_m + accumulated_bars) > (bbt.bars - 1)) {
+                                       break;
+                               }
+                               accumulated_beats = m->beat();
                                accumulated_bars += bars_to_m;
                        }
                        prev_ms = m;
@@ -1591,7 +1703,7 @@ TempoMap::bbt_to_beats_locked (const Metrics& metrics, const Timecode::BBT_Time&
 }
 
 Timecode::BBT_Time
-TempoMap::beats_to_bbt (double beats)
+TempoMap::beats_to_bbt (const double& beats)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
@@ -1599,11 +1711,11 @@ TempoMap::beats_to_bbt (double beats)
 }
 
 Timecode::BBT_Time
-TempoMap::beats_to_bbt_locked (const Metrics& metrics, const double& beats) const
+TempoMap::beats_to_bbt_locked (const Metrics& metrics, const double& b) const
 {
        /* CALLER HOLDS READ LOCK */
-
        MeterSection* prev_ms = 0;
+       const double beats = (b < 0.0) ? 0.0 : b;
        uint32_t accumulated_bars = 0;
        double accumulated_beats = 0.0;
 
@@ -1658,7 +1770,7 @@ TempoMap::beats_to_bbt_locked (const Metrics& metrics, const double& beats) cons
 }
 
 Timecode::BBT_Time
-TempoMap::pulse_to_bbt (double pulse)
+TempoMap::pulse_to_bbt (const double& pulse)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
        MeterSection* prev_ms = 0;
@@ -1715,51 +1827,7 @@ TempoMap::pulse_to_bbt (double pulse)
 }
 
 double
-TempoMap::beat_offset_at (const Metrics& metrics, const double& beat) const
-{
-       MeterSection* prev_m = 0;
-       double beat_off = 0.0;
-
-       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
-               MeterSection* m = 0;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (m->pulse() > beat) {
-                               break;
-                       }
-
-                       if (prev_m && m->position_lock_style() == AudioTime) {
-                               beat_off += ((m->pulse() - prev_m->pulse()) / prev_m->note_divisor()) - floor ((m->pulse() - prev_m->pulse()) / prev_m->note_divisor());
-                       }
-
-                       prev_m = m;
-               }
-       }
-
-       return beat_off;
-}
-
-frameoffset_t
-TempoMap::frame_offset_at (const Metrics& metrics, const framepos_t& frame) const
-{
-       frameoffset_t frame_off = 0;
-
-       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
-               MeterSection* m = 0;
-               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
-                       if (m->frame() > frame) {
-                               break;
-                       }
-                       if (m->position_lock_style() == AudioTime) {
-                               frame_off += frame_at_pulse_locked (metrics, m->pulse()) - m->frame();
-                       }
-               }
-       }
-
-       return frame_off;
-}
-
-double
-TempoMap::beat_at_frame (framecnt_t frame) const
+TempoMap::beat_at_frame (const framecnt_t& frame) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
        return beat_at_frame_locked (_metrics, frame);
@@ -1768,10 +1836,10 @@ TempoMap::beat_at_frame (framecnt_t frame) const
 double
 TempoMap::beat_at_frame_locked (const Metrics& metrics, const framecnt_t& frame) const
 {
-       framecnt_t const offset_frame = frame + frame_offset_at (metrics, frame);
-       double const pulse = pulse_at_frame_locked (metrics, offset_frame);
+       //framecnt_t const offset_frame = frame + frame_offset_at (metrics, frame);
+       double const pulse = pulse_at_frame_locked (metrics, frame);
 
-       return beat_at_pulse (metrics, pulse);
+       return beat_at_pulse_locked (metrics, pulse);
 }
 
 double
@@ -1784,13 +1852,14 @@ TempoMap::pulse_at_frame_locked (const Metrics& metrics, const framecnt_t& frame
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (prev_ts && t->frame() > frame) {
                                /*the previous ts is the one containing the frame */
                                double const ret = prev_ts->pulse_at_frame (frame, _frame_rate);
                                return ret;
                        }
-
                        accumulated_pulses = t->pulse();
                        prev_ts = t;
                }
@@ -1803,7 +1872,7 @@ TempoMap::pulse_at_frame_locked (const Metrics& metrics, const framecnt_t& frame
 }
 
 framecnt_t
-TempoMap::frame_at_beat (double beat) const
+TempoMap::frame_at_beat (const double& beat) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
        return frame_at_beat_locked (_metrics, beat);
@@ -1812,9 +1881,9 @@ TempoMap::frame_at_beat (double beat) const
 framecnt_t
 TempoMap::frame_at_beat_locked (const Metrics& metrics, const double& beat) const
 {
-       framecnt_t const frame = frame_at_pulse_locked (metrics, pulse_at_beat (metrics, beat));
-       frameoffset_t const frame_off = frame_offset_at (metrics, frame);
-       return frame - frame_off;
+       framecnt_t const frame = frame_at_pulse_locked (metrics, pulse_at_beat_locked (metrics, beat));
+       //frameoffset_t const frame_off = frame_offset_at (metrics, frame);
+       return frame;
 }
 
 framecnt_t
@@ -1823,22 +1892,25 @@ TempoMap::frame_at_pulse_locked (const Metrics& metrics, const double& pulse) co
        /* HOLD THE READER LOCK */
 
        const TempoSection* prev_ts = 0;
-       double accumulated_beats = 0.0;
+       double accumulated_pulses = 0.0;
 
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
 
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (prev_ts && t->pulse() > pulse) {
                                return prev_ts->frame_at_pulse (pulse, _frame_rate);
                        }
 
-                       accumulated_beats = t->pulse();
+                       accumulated_pulses = t->pulse();
                        prev_ts = t;
                }
        }
        /* must be treated as constant, irrespective of _type */
-       double const pulses_in_section = pulse - accumulated_beats;
+       double const pulses_in_section = pulse - accumulated_pulses;
        double const dtime = pulses_in_section * prev_ts->frames_per_pulse (_frame_rate);
 
        framecnt_t const ret = (framecnt_t) floor (dtime) + prev_ts->frame();
@@ -1846,6 +1918,54 @@ TempoMap::frame_at_pulse_locked (const Metrics& metrics, const double& pulse) co
        return ret;
 }
 
+double
+TempoMap::beat_offset_at (const Metrics& metrics, const double& beat) const
+{
+       MeterSection* prev_m = 0;
+       double beat_off = first_meter().pulse();
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               MeterSection* m = 0;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (prev_m) {
+                               if (m->beat() > beat) {
+                                       break;
+                               }
+
+                               if (m->position_lock_style() == AudioTime) {
+                                       beat_off += ((m->beat() - prev_m->beat()) / prev_m->note_divisor()) - floor (m->pulse() - prev_m->pulse());
+                               }
+                       }
+                       prev_m = m;
+               }
+       }
+
+       return beat_off;
+}
+
+frameoffset_t
+TempoMap::frame_offset_at (const Metrics& metrics, const framepos_t& frame) const
+{
+       frameoffset_t frame_off = 0;
+       MeterSection* prev_m = 0;
+
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               MeterSection* m = 0;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (m->frame() > frame) {
+                               break;
+                       }
+                       if (prev_m && m->position_lock_style() == AudioTime) {
+                               const double pulse = prev_m->pulse() + ((m->beat() - prev_m->beat()) / prev_m->note_divisor());
+                               frame_off += frame_at_pulse_locked (metrics, pulse) - m->frame();
+                       }
+                       prev_m = m;
+               }
+       }
+
+       return frame_off;
+}
+
 framepos_t
 TempoMap::frame_time (const BBT_Time& bbt)
 {
@@ -1858,7 +1978,7 @@ TempoMap::frame_time (const BBT_Time& bbt)
                throw std::logic_error ("beats are counted from one");
        }
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       double beat = bbt_to_beats_locked (_metrics, bbt);
+       double const beat = bbt_to_beats_locked (_metrics, bbt);
        framecnt_t const frame = frame_at_beat_locked (_metrics, beat);
        return frame;
 }
@@ -1868,7 +1988,7 @@ TempoMap::frame_time_locked (const Metrics& metrics, const BBT_Time& bbt) const
 {
        /* HOLD THE READER LOCK */
 
-       framepos_t const ret = frame_at_pulse_locked (metrics, pulse_at_beat (metrics, bbt_to_beats_locked (metrics, bbt)));
+       framepos_t const ret = frame_at_pulse_locked (metrics, pulse_at_beat_locked (metrics, bbt_to_beats_locked (metrics, bbt)));
 
        return ret;
 }
@@ -1881,22 +2001,22 @@ TempoMap::check_solved (Metrics& metrics, bool by_frame)
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
                TempoSection* t;
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (prev_ts) {
                                if ((by_frame && t->frame() < prev_ts->frame()) || (!by_frame && t->pulse() < prev_ts->pulse())) {
                                        return false;
                                }
-                               if (by_frame && t->frame() != prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate)) {
+
+                               if (t->frame() == prev_ts->frame()) {
                                        return false;
                                }
-                               /*
-                               if (!by_frame && fabs (t->pulse() - prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate)) > 0.00001) {
-                                       std::cerr << "beat precision too low for bpm: " << t->beats_per_minute() << std::endl <<
-                                               " |error          :" << t->pulse() - prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate) << std::endl <<
-                                               "|frame at beat   :" << prev_ts->frame_at_pulse (t->pulse(), _frame_rate) << std::endl <<
-                                               " |frame at tempo : " << prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate) << std::endl;
+
+                               /* precision check ensures pulses and frames align independent of lock style.*/
+                               if (by_frame && t->frame() != prev_ts->frame_at_pulse (t->pulse(), _frame_rate)) {
                                        return false;
                                }
-                               */
                        }
                        prev_ts = t;
                }
@@ -1905,18 +2025,59 @@ TempoMap::check_solved (Metrics& metrics, bool by_frame)
        return true;
 }
 
+bool
+TempoMap::set_active_tempos (const Metrics& metrics, const framepos_t& frame)
+{
+       for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
+               TempoSection* t;
+               if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->movable()) {
+                               t->set_active (true);
+                               continue;
+                       }
+                       if (t->movable() && t->active () && t->position_lock_style() == AudioTime && t->frame() < frame) {
+                               t->set_active (false);
+                               t->set_pulse (0.0);
+                       } else if (t->movable() && t->position_lock_style() == AudioTime && t->frame() > frame) {
+                               t->set_active (true);
+                       } else if (t->movable() && t->position_lock_style() == AudioTime && t->frame() == frame) {
+                               return false;
+                       }
+               }
+       }
+       return true;
+}
+
 bool
 TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm, const framepos_t& frame)
 {
        TempoSection* prev_ts = 0;
        TempoSection* section_prev = 0;
-       MetricSectionFrameSorter fcmp;
-       MetricSectionSorter cmp;
+       framepos_t first_m_frame = 0;
 
+       for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (!m->movable()) {
+                               first_m_frame = m->frame();
+                               break;
+                       }
+               }
+       }
+       if (section->movable() && frame <= first_m_frame) {
+               return false;
+       } else {
+               section->set_active (true);
+       }
        section->set_frame (frame);
+
        for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
                TempoSection* t;
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (prev_ts) {
                                if (t == section) {
                                        section_prev = prev_ts;
@@ -1935,7 +2096,7 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
        }
 
        if (section_prev) {
-               section_prev->set_c_func (section_prev->compute_c_func_pulse (section->pulses_per_minute(), section->pulse(), _frame_rate));
+               section_prev->set_c_func (section_prev->compute_c_func_frame (section->pulses_per_minute(), frame, _frame_rate));
                section->set_pulse (section_prev->pulse_at_frame (frame, _frame_rate));
        }
 
@@ -1953,6 +2114,7 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                return true;
        }
 
+       MetricSectionFrameSorter fcmp;
        imaginary.sort (fcmp);
        if (section->position_lock_style() == MusicTime) {
                /* we're setting the frame */
@@ -1967,6 +2129,7 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                return true;
        }
 
+       MetricSectionSorter cmp;
        imaginary.sort (cmp);
        if (section->position_lock_style() == MusicTime) {
                /* we're setting the frame */
@@ -1980,24 +2143,25 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                recompute_meters (imaginary);
                return true;
        }
-
        //dump (imaginary, std::cerr);
+
        return false;
 }
 
 bool
-TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm, const double& beat)
+TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm, const double& pulse)
 {
-       MetricSectionSorter cmp;
-       MetricSectionFrameSorter fcmp;
        TempoSection* prev_ts = 0;
        TempoSection* section_prev = 0;
 
-       section->set_pulse (beat);
+       section->set_pulse (pulse);
 
        for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
                TempoSection* t;
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (prev_ts) {
                                if (t == section) {
                                        section_prev = prev_ts;
@@ -2015,12 +2179,12 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                }
        }
        if (section_prev) {
-               section_prev->set_c_func (section_prev->compute_c_func_pulse (section->pulses_per_minute(), section->pulse(), _frame_rate));
-               section->set_frame (section_prev->frame_at_pulse (section->pulse(), _frame_rate));
+               section_prev->set_c_func (section_prev->compute_c_func_pulse (section->pulses_per_minute(), pulse, _frame_rate));
+               section->set_frame (section_prev->frame_at_pulse (pulse, _frame_rate));
        }
 
        if (section->position_lock_style() == AudioTime) {
-               /* we're setting the beat */
+               /* we're setting the pulse */
                section->set_position_lock_style (MusicTime);
                recompute_tempos (imaginary);
                section->set_position_lock_style (AudioTime);
@@ -2032,9 +2196,10 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                return true;
        }
 
+       MetricSectionSorter cmp;
        imaginary.sort (cmp);
        if (section->position_lock_style() == AudioTime) {
-               /* we're setting the beat */
+               /* we're setting the pulse */
                section->set_position_lock_style (MusicTime);
                recompute_tempos (imaginary);
                section->set_position_lock_style (AudioTime);
@@ -2047,9 +2212,10 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
                return true;
        }
 
+       MetricSectionFrameSorter fcmp;
        imaginary.sort (fcmp);
        if (section->position_lock_style() == AudioTime) {
-               /* we're setting the beat */
+               /* we're setting the pulse */
                section->set_position_lock_style (MusicTime);
                recompute_tempos (imaginary);
                section->set_position_lock_style (AudioTime);
@@ -2068,86 +2234,143 @@ TempoMap::solve_map (Metrics& imaginary, TempoSection* section, const Tempo& bpm
 }
 
 void
-TempoMap::solve_map (Metrics& imaginary, MeterSection* section, const Meter& mt, const double& beat)
+TempoMap::solve_map (Metrics& imaginary, MeterSection* section, const Meter& mt, const framepos_t& frame)
 {
        MeterSection* prev_ms = 0;
 
-       pair<double, BBT_Time> b_bbt = make_pair (beat, beats_to_bbt_locked (imaginary, beat));
-       section->set_pulse (b_bbt);
-       MetricSectionSorter cmp;
-       imaginary.sort (cmp);
+       if (!section->movable()) {
+               /* lock the first tempo to our first meter */
+               if (!set_active_tempos (imaginary, frame)) {
+                       return;
+               }
+               TempoSection* first_t = &first_tempo();
+               Metrics future_map;
+               TempoSection* new_section = copy_metrics_and_point (future_map, first_t);
+
+               new_section->set_frame (frame);
+               new_section->set_pulse (0.0);
+               new_section->set_active (true);
+
+               if (solve_map (future_map, new_section, Tempo (new_section->beats_per_minute(), new_section->note_type()), frame)) {
+                       first_t->set_frame (frame);
+                       first_t->set_pulse (0.0);
+                       first_t->set_active (true);
+                       solve_map (imaginary, first_t, Tempo (first_t->beats_per_minute(), first_t->note_type()), frame);
+               } else {
+                       return;
+               }
+       }
+
+       uint32_t accumulated_bars = 0;
+
+       section->set_frame (frame);
 
        for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
                MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
                        if (prev_ms) {
-                               if (m == section){
-                                       section->set_frame (frame_at_pulse_locked (imaginary, pulse_at_beat (imaginary, beat)));
-                                       prev_ms = section;
-                                       continue;
+                               const double beats_in_m = (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
+                               accumulated_bars += (beats_in_m + 1) / prev_ms->divisions_per_bar();
+                       }
+                       if (m == section){
+                               /*
+                                 here we set the beat for this frame.
+                                 we're going to set it 'incorrectly' to the next integer and use this difference
+                                 to find the meter's pulse later.
+                                 (meters should fall on absolute beats to keep us sane)
+                               */
+                               double pulse = 0.0;
+                               pair<double, BBT_Time> b_bbt;
+                               if (m->movable()) {
+                                       double beats = ((pulse_at_frame_locked (imaginary, frame) - prev_ms->pulse()) * prev_ms->note_divisor()) - prev_ms->beat();
+                                       b_bbt = make_pair (ceil (beats), BBT_Time (accumulated_bars + 1, 1, 0));
+                                       const double true_pulse = prev_ms->pulse() + ((ceil (beats) - prev_ms->beat()) / prev_ms->note_divisor());
+                                       const double pulse_off = true_pulse - ((beats - prev_ms->beat()) / prev_ms->note_divisor());
+                                       pulse = true_pulse - pulse_off;
+                               } else {
+                                       b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
                                }
+                               m->set_beat (b_bbt);
+                               m->set_pulse (pulse);
+                               prev_ms = m;
+                               continue;
+                       }
+                       if (prev_ms) {
                                if (m->position_lock_style() == MusicTime) {
-                                       m->set_frame (frame_at_pulse_locked (imaginary, m->pulse()));
+                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
+                                       m->set_frame (frame_at_pulse_locked (imaginary, pulse));
+                                       m->set_pulse (pulse);
                                } else {
-                                       pair<double, BBT_Time> b_bbt = make_pair (pulse_at_frame_locked (imaginary, m->frame()), BBT_Time (1, 1, 0));
-                                       b_bbt.second = beats_to_bbt_locked (imaginary, beat_at_pulse (imaginary, b_bbt.first));
-                                       m->set_pulse (b_bbt);
+                                       if (!m->movable()) {
+                                               pair<double, BBT_Time> b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
+                                               m->set_beat (b_bbt);
+                                       }
+                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
+                                       m->set_pulse (pulse);
                                }
                        }
                        prev_ms = m;
                }
        }
 
-       if (section->position_lock_style() == AudioTime) {
-               /* we're setting the beat */
-               section->set_position_lock_style (MusicTime);
-               recompute_meters (imaginary);
+       if (section->position_lock_style() == MusicTime) {
+               /* we're setting the frame */
                section->set_position_lock_style (AudioTime);
+               recompute_meters (imaginary);
+               section->set_position_lock_style (MusicTime);
        } else {
                recompute_meters (imaginary);
        }
+       //dump (imaginary, std::cerr);
 }
 
 void
-TempoMap::solve_map (Metrics& imaginary, MeterSection* section, const Meter& mt, const framepos_t& frame)
+TempoMap::solve_map (Metrics& imaginary, MeterSection* section, const Meter& mt, const double& pulse)
 {
        MeterSection* prev_ms = 0;
-       section->set_frame (frame);
+       double accumulated_beats = 0.0;
+       uint32_t accumulated_bars = 0;
+
+       section->set_pulse (pulse);
 
        for (Metrics::iterator i = imaginary.begin(); i != imaginary.end(); ++i) {
                MeterSection* m;
                if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
                        if (prev_ms) {
-                               if (m == section){
-                                       /*
-                                         here we define the beat for this frame.
-                                         we're going to set it 'incorrectly' to the next integer and use this 'error'
-                                         as an offset to the map as far as users of the public methods are concerned.
-                                         (meters should go on absolute beats to keep us sane)
-                                       */
-                                       double const pulse_at_f = ceil (pulse_at_frame_locked (imaginary, m->frame()));
-                                       pair<double, BBT_Time> b_bbt = make_pair (pulse_at_f, beats_to_bbt_locked (imaginary, beat_at_pulse (imaginary, pulse_at_f)));
-                                       m->set_pulse (b_bbt);
-                                       prev_ms = m;
-                                       continue;
-                               }
+                               double const beats_in_m = (m->pulse() - prev_ms->pulse()) * prev_ms->note_divisor();
+                               accumulated_beats += beats_in_m;
+                               accumulated_bars += (beats_in_m + 1) / prev_ms->divisions_per_bar();
+                       }
+                       if (m == section){
+                               section->set_frame (frame_at_pulse_locked (imaginary, pulse));
+                               pair<double, BBT_Time> b_bbt = make_pair (accumulated_beats, BBT_Time (accumulated_bars + 1, 1, 0));
+                               section->set_beat (b_bbt);
+                               prev_ms = section;
+                               continue;
+                       }
+                       if (prev_ms) {
                                if (m->position_lock_style() == MusicTime) {
-                                       m->set_frame (frame_at_pulse_locked (imaginary, m->pulse()));
+                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
+                                       m->set_frame (frame_at_pulse_locked (imaginary, pulse));
+                                       m->set_pulse (pulse);
                                } else {
-                                       double const pulse_at_f = ceil (pulse_at_frame_locked (imaginary, frame));
-                                       pair<double, BBT_Time> b_bbt = make_pair (pulse_at_f, beats_to_bbt_locked (imaginary, beat_at_pulse (imaginary, pulse_at_f)));
-                                       m->set_pulse (b_bbt);
+                                       if (!m->movable()) {
+                                               pair<double, BBT_Time> b_bbt = make_pair (0.0, BBT_Time (1, 1, 0));
+                                               m->set_beat (b_bbt);
+                                       }
+                                       const double pulse = prev_ms->pulse() + (m->beat() - prev_ms->beat()) / prev_ms->note_divisor();
+                                       m->set_pulse (pulse);
                                }
                        }
                        prev_ms = m;
                }
        }
 
-       if (section->position_lock_style() == MusicTime) {
-               /* we're setting the frame */
-               section->set_position_lock_style (AudioTime);
-               recompute_meters (imaginary);
+       if (section->position_lock_style() == AudioTime) {
+               /* we're setting the pulse */
                section->set_position_lock_style (MusicTime);
+               recompute_meters (imaginary);
+               section->set_position_lock_style (AudioTime);
        } else {
                recompute_meters (imaginary);
        }
@@ -2275,6 +2498,57 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, RoundMode dir)
        return ret_frame;
 }
 
+void
+TempoMap::round_bbt (BBT_Time& when, const int32_t& sub_num)
+{
+       if (sub_num == -1) {
+               const double bpb = meter_section_at (bbt_to_beats_locked (_metrics, when)).divisions_per_bar();
+               if ((double) when.beats > bpb / 2.0) {
+                       ++when.bars;
+               }
+               when.beats = 1;
+               when.ticks = 0;
+               return;
+       } else if (sub_num == 0) {
+               const double bpb = meter_section_at (bbt_to_beats_locked (_metrics, when)).divisions_per_bar();
+               if ((double) when.ticks > BBT_Time::ticks_per_beat / 2.0) {
+                       ++when.beats;
+                       while ((double) when.beats > bpb) {
+                               ++when.bars;
+                               when.beats -= (uint32_t) floor (bpb);
+                       }
+               }
+               when.ticks = 0;
+               return;
+       }
+       const uint32_t ticks_one_subdivisions_worth = BBT_Time::ticks_per_beat / sub_num;
+       double rem;
+       if ((rem = fmod ((double) when.ticks, (double) ticks_one_subdivisions_worth)) > (ticks_one_subdivisions_worth / 2.0)) {
+               /* closer to the next subdivision, so shift forward */
+
+               when.ticks = when.ticks + (ticks_one_subdivisions_worth - rem);
+
+               if (when.ticks > Timecode::BBT_Time::ticks_per_beat) {
+                       ++when.beats;
+                       when.ticks -= Timecode::BBT_Time::ticks_per_beat;
+               }
+
+       } else if (rem > 0) {
+               /* closer to previous subdivision, so shift backward */
+
+               if (rem > when.ticks) {
+                       if (when.beats == 0) {
+                               /* can't go backwards past zero, so ... */
+                       }
+                       /* step back to previous beat */
+                       --when.beats;
+                       when.ticks = Timecode::BBT_Time::ticks_per_beat - rem;
+               } else {
+                       when.ticks = when.ticks - rem;
+               }
+       }
+}
+
 framepos_t
 TempoMap::round_to_type (framepos_t frame, RoundMode dir, BBTPointType type)
 {
@@ -2334,16 +2608,19 @@ TempoMap::get_grid (vector<TempoMap::BBTPoint>& points,
                    framepos_t lower, framepos_t upper)
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       uint32_t const upper_beat = (uint32_t) ceil (beat_at_frame_locked (_metrics, upper));
-       uint32_t cnt = floor (beat_at_frame_locked (_metrics, lower));
-
+       int32_t const upper_beat = (int32_t) ceil (beat_at_frame_locked (_metrics, upper));
+       int32_t cnt = floor (beat_at_frame_locked (_metrics, lower));
+       /* although the map handles negative beats, bbt doesn't. */
+       if (cnt < 0.0) {
+               cnt = 0.0;
+       }
        while (cnt <= upper_beat) {
                framecnt_t pos = frame_at_beat_locked (_metrics, cnt);
                TempoSection const tempo = tempo_section_at_locked (pos);
                MeterSection const meter = meter_section_at_locked (pos);
                BBT_Time const bbt = beats_to_bbt (cnt);
-
-               points.push_back (BBTPoint (meter, Tempo (tempo.beats_per_minute(), tempo.note_type()), pos, bbt.bars, bbt.beats));
+               BBTPoint point = BBTPoint (meter, tempo_at_locked (pos), pos, bbt.bars, bbt.beats, tempo.get_c_func());
+               points.push_back (point);
                ++cnt;
        }
 }
@@ -2365,7 +2642,9 @@ TempoMap::tempo_section_at_locked (framepos_t frame) const
                TempoSection* t;
 
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-
+                       if (!t->active()) {
+                               continue;
+                       }
                        if (t->frame() > frame) {
                                break;
                        }
@@ -2387,7 +2666,7 @@ TempoMap::tempo_section_at_locked (framepos_t frame) const
    do that stuff based on the beat_at_frame and frame_at_beat api
 */
 double
-TempoMap::frames_per_beat_at (framepos_t frame, framecnt_t sr) const
+TempoMap::frames_per_beat_at (const framepos_t& frame, const framecnt_t& sr) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
 
@@ -2399,7 +2678,9 @@ TempoMap::frames_per_beat_at (framepos_t frame, framecnt_t sr) const
                TempoSection* t;
 
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
-
+                       if (!t->active()) {
+                               continue;
+                       }
                        if ((*i)->frame() > frame) {
                                ts_after = t;
                                break;
@@ -2415,10 +2696,15 @@ TempoMap::frames_per_beat_at (framepos_t frame, framecnt_t sr) const
 }
 
 const Tempo
-TempoMap::tempo_at (framepos_t frame) const
+TempoMap::tempo_at (const framepos_t& frame) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock);
-       frameoffset_t const frame_off = frame + frame_offset_at (_metrics, frame);
+       return tempo_at_locked (frame);
+}
+
+const Tempo
+TempoMap::tempo_at_locked (const framepos_t& frame) const
+{
        TempoSection* prev_ts = 0;
 
        Metrics::const_iterator i;
@@ -2426,6 +2712,9 @@ TempoMap::tempo_at (framepos_t frame) const
        for (i = _metrics.begin(); i != _metrics.end(); ++i) {
                TempoSection* t;
                if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
+                       if (!t->active()) {
+                               continue;
+                       }
                        if ((prev_ts) && t->frame() > frame) {
                                /* t is the section past frame */
                                double const ret = prev_ts->tempo_at_frame (frame, _frame_rate) * prev_ts->note_type();
@@ -2452,20 +2741,20 @@ TempoMap::meter_section_at (framepos_t frame) const
 const MeterSection&
 TempoMap::meter_section_at_locked (framepos_t frame) const
 {
-       framepos_t const frame_off = frame + frame_offset_at (_metrics, frame);
+       //framepos_t const frame_off = frame + frame_offset_at (_metrics, frame);
        Metrics::const_iterator i;
        MeterSection* prev = 0;
 
        for (i = _metrics.begin(); i != _metrics.end(); ++i) {
-               MeterSection* t;
+               MeterSection* m;
 
-               if ((t = dynamic_cast<MeterSection*> (*i)) != 0) {
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
 
-                       if ((*i)->frame() > frame_off) {
+                       if (prev && (*i)->frame() > frame) {
                                break;
                        }
 
-                       prev = t;
+                       prev = m;
                }
        }
 
@@ -2480,12 +2769,29 @@ TempoMap::meter_section_at_locked (framepos_t frame) const
 const Meter&
 TempoMap::meter_at (framepos_t frame) const
 {
-       framepos_t const frame_off = frame + frame_offset_at (_metrics, frame);
-       TempoMetric m (metric_at (frame_off));
-
+       TempoMetric m (metric_at (frame));
        return m.meter();
 }
 
+const MeterSection&
+TempoMap::meter_section_at (const double& beat) const
+{
+       MeterSection* prev_ms = 0;
+       Glib::Threads::RWLock::ReaderLock lm (lock);
+
+       for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+               MeterSection* m;
+               if ((m = dynamic_cast<MeterSection*> (*i)) != 0) {
+                       if (prev_ms && m->beat() > beat) {
+                               break;
+                       }
+                       prev_ms = m;
+               }
+
+       }
+       return *prev_ms;
+}
+
 XMLNode&
 TempoMap::get_state ()
 {
@@ -2511,7 +2817,6 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
                XMLNodeList nlist;
                XMLNodeConstIterator niter;
                Metrics old_metrics (_metrics);
-               MeterSection* last_meter = 0;
                _metrics.clear();
 
                nlist = node.children();
@@ -2524,12 +2829,6 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
                                try {
                                        TempoSection* ts = new TempoSection (*child);
                                        _metrics.push_back (ts);
-
-                                       if (ts->bar_offset() < 0.0) {
-                                               if (last_meter) {
-                                                       //ts->update_bar_offset_from_bbt (*last_meter);
-                                               }
-                                       }
                                }
 
                                catch (failed_constructor& err){
@@ -2543,7 +2842,6 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
                                try {
                                        MeterSection* ms = new MeterSection (*child);
                                        _metrics.push_back (ms);
-                                       last_meter = ms;
                                }
 
                                catch (failed_constructor& err) {
@@ -2560,20 +2858,28 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
                }
                /* check for legacy sessions where bbt was the base musical unit for tempo */
                for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
-                       MeterSection* prev_ms;
-                       TempoSection* prev_ts;
-                       if ((prev_ms = dynamic_cast<MeterSection*>(*i)) != 0) {
-                               if (prev_ms->pulse() < 0.0) {
+                       MeterSection* m;
+                       TempoSection* t;
+                       MeterSection* prev_ms = 0;
+                       TempoSection* prev_ts = 0;
+                       if ((m = dynamic_cast<MeterSection*>(*i)) != 0) {
+                               if (prev_ms && prev_ms->pulse() < 0.0) {
                                        /*XX we cannot possibly make this work??. */
-                                       pair<double, BBT_Time> start = make_pair (((prev_ms->bbt().bars - 1) * 4.0) + (prev_ms->bbt().beats - 1) + (prev_ms->bbt().ticks / BBT_Time::ticks_per_beat), prev_ms->bbt());
-                                       prev_ms->set_pulse (start);
+                                       pair<double, BBT_Time> start = make_pair (((prev_ms->bbt().bars - 1) * prev_ms->note_divisor()) + (prev_ms->bbt().beats - 1) + (prev_ms->bbt().ticks / BBT_Time::ticks_per_beat), prev_ms->bbt());
+                                       prev_ms->set_beat (start);
+                                       const double start_pulse = ((prev_ms->bbt().bars - 1) * prev_ms->note_divisor()) + (prev_ms->bbt().beats - 1) + (prev_ms->bbt().ticks / BBT_Time::ticks_per_beat);
+                                       prev_ms->set_pulse (start_pulse);
                                }
-                       } else if ((prev_ts = dynamic_cast<TempoSection*>(*i)) != 0) {
-                               if (prev_ts->pulse() < 0.0) {
-                                       double const start = ((prev_ts->legacy_bbt().bars - 1) * 4.0) + (prev_ts->legacy_bbt().beats - 1) + (prev_ts->legacy_bbt().ticks / BBT_Time::ticks_per_beat);
+                               prev_ms = m;
+                       } else if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+                               if (!t->active()) {
+                                       continue;
+                               }
+                               if (prev_ts && prev_ts->pulse() < 0.0) {
+                                       double const start = ((prev_ts->legacy_bbt().bars - 1) * prev_ms->note_divisor()) + (prev_ts->legacy_bbt().beats - 1) + (prev_ts->legacy_bbt().ticks / BBT_Time::ticks_per_beat);
                                        prev_ts->set_pulse (start);
-
                                }
+                               prev_ts = t;
                        }
                }
                /* check for multiple tempo/meters at the same location, which
@@ -2613,7 +2919,7 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
 }
 
 void
-TempoMap::dump (Metrics& metrics, std::ostream& o) const
+TempoMap::dump (const Metrics& metrics, std::ostream& o) const
 {
        Glib::Threads::RWLock::ReaderLock lm (lock, Glib::Threads::TRY_LOCK);
        const MeterSection* m;
@@ -2623,20 +2929,20 @@ TempoMap::dump (Metrics& metrics, std::ostream& o) const
        for (Metrics::const_iterator i = metrics.begin(); i != metrics.end(); ++i) {
 
                if ((t = dynamic_cast<const TempoSection*>(*i)) != 0) {
-                       o << "Tempo @ " << *i << " (Bar-offset: " << t->bar_offset() << ") " << t->beats_per_minute() << " BPM (pulse = 1/" << t->note_type() << ") at " << t->pulse() << " frame= " << t->frame() << " (movable? "
-                         << t->movable() << ')' << endl;
+                       o << "Tempo @ " << *i << t->beats_per_minute() << " BPM (pulse = 1/" << t->note_type() << ") at " << t->pulse() << " frame= " << t->frame() << " (movable? "
+                         << t->movable() << ')' << " pos lock: " << enum_2_string (t->position_lock_style()) << std::endl;
+                       o << "current      : " << t->beats_per_minute() << " | " << t->pulse() << " | " << t->frame() << std::endl;
                        if (prev_ts) {
-                               o << "current      : " << t->beats_per_minute() << " | " << t->pulse() << " | " << t->frame() << std::endl;
                                o << "previous     : " << prev_ts->beats_per_minute() << " | " << prev_ts->pulse() << " | " << prev_ts->frame() << std::endl;
-                               o << "calculated   : " << prev_ts->tempo_at_pulse (t->pulse()) << " | " << prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate) <<  " | " << prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate) << std::endl;
-                               o << "------" << std::endl;
+                               o << "calculated   : " << prev_ts->tempo_at_pulse (t->pulse()) *  prev_ts->note_type() << " | " << prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate) <<  " | " << prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate) << std::endl;
                        }
+                       prev_ts = t;
                } else if ((m = dynamic_cast<const MeterSection*>(*i)) != 0) {
                        o << "Meter @ " << *i << ' ' << m->divisions_per_bar() << '/' << m->note_divisor() << " at " << m->bbt() << " frame= " << m->frame()
-                         << " (movable? " << m->movable() << ')' << endl;
+                         << " pulse: " << m->pulse() <<  " beat : " << m->beat() << " pos lock: " << enum_2_string (m->position_lock_style()) << " (movable? " << m->movable() << ')' << endl;
                }
-               prev_ts = t;
        }
+       o << "------" << std::endl;
 }
 
 int
@@ -2711,6 +3017,9 @@ TempoMap::insert_time (framepos_t where, framecnt_t amount)
                        if (prev) {
                                if (ts){
                                        if ((t = dynamic_cast<TempoSection*>(prev)) != 0) {
+                                               if (!t->active()) {
+                                                       continue;
+                                               }
                                                ts->set_pulse (t->pulse());
                                        }
                                        if ((m = dynamic_cast<MeterSection*>(prev)) != 0) {
@@ -2721,12 +3030,18 @@ TempoMap::insert_time (framepos_t where, framecnt_t amount)
                                }
                                if (ms) {
                                        if ((m = dynamic_cast<MeterSection*>(prev)) != 0) {
-                                               pair<double, BBT_Time> start = make_pair (m->pulse(), m->bbt());
-                                               ms->set_pulse (start);
+                                               pair<double, BBT_Time> start = make_pair (m->beat(), m->bbt());
+                                               ms->set_beat (start);
+                                               ms->set_pulse (m->pulse());
                                        }
                                        if ((t = dynamic_cast<TempoSection*>(prev)) != 0) {
-                                               pair<double, BBT_Time> start = make_pair (t->pulse(), beats_to_bbt_locked (_metrics, t->pulse()));
-                                               ms->set_pulse (start);
+                                               if (!t->active()) {
+                                                       continue;
+                                               }
+                                               const double beat = beat_at_pulse_locked (_metrics, t->pulse());
+                                               pair<double, BBT_Time> start = make_pair (beat, beats_to_bbt_locked (_metrics, beat));
+                                               ms->set_beat (start);
+                                               ms->set_pulse (t->pulse());
                                        }
                                        ms->set_frame (prev->frame());
                                }
@@ -2739,6 +3054,9 @@ TempoMap::insert_time (framepos_t where, framecnt_t amount)
                        // cerr << bbt << endl;
 
                        if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+                               if (!t->active()) {
+                                       continue;
+                               }
                                t->set_pulse (pulse_at_frame_locked (_metrics, m->frame()));
                                tempo = t;
                                // cerr << "NEW TEMPO, frame = " << (*i)->frame() << " beat = " << (*i)->pulse() <<endl;
@@ -2764,8 +3082,9 @@ TempoMap::insert_time (framepos_t where, framecnt_t amount)
                                                bbt.beats = 1;
                                        }
                                }
-                               pair<double, BBT_Time> start = make_pair (pulse_at_frame_locked (_metrics, m->frame()), bbt);
-                               m->set_pulse (start);
+                               pair<double, BBT_Time> start = make_pair (beat_at_frame_locked (_metrics, m->frame()), bbt);
+                               m->set_beat (start);
+                               m->set_pulse (pulse_at_frame_locked (_metrics, m->frame()));
                                meter = m;
                                // cerr << "NEW METER, frame = " << (*i)->frame() << " beat = " << (*i)->pulse() <<endl;
                        } else {
@@ -2890,7 +3209,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op) const
 Evoral::Beats
 TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 {
-       return Evoral::Beats(beat_at_frame (pos + distance) - beat_at_frame (pos));
+       return Evoral::Beats (beat_at_frame (pos + distance) - beat_at_frame (pos));
 }
 
 struct bbtcmp {
@@ -2920,7 +3239,7 @@ operator<< (std::ostream& o, const MetricSection& section) {
        if ((ts = dynamic_cast<const TempoSection*> (&section)) != 0) {
                o << *((const Tempo*) ts);
        } else if ((ms = dynamic_cast<const MeterSection*> (&section)) != 0) {
-               //o << *((const Meter*) ms);
+               o << *((const Meter*) ms);
        }
 
        return o;