Delayline naming -- for debug purposes
[ardour.git] / libs / ardour / route.cc
index d405dd8f082ee527837b3055f07832eed0a44c7e..2d24ac4ac654eb180747841178403802b2afc589 100644 (file)
@@ -47,6 +47,8 @@
 #include "ardour/capturing_processor.h"
 #include "ardour/debug.h"
 #include "ardour/delivery.h"
+#include "ardour/disk_reader.h"
+#include "ardour/disk_writer.h"
 #include "ardour/event_type_map.h"
 #include "ardour/gain_control.h"
 #include "ardour/internal_return.h"
@@ -55,6 +57,7 @@
 #include "ardour/delayline.h"
 #include "ardour/midi_buffer.h"
 #include "ardour/midi_port.h"
+#include "ardour/monitor_control.h"
 #include "ardour/monitor_processor.h"
 #include "ardour/pannable.h"
 #include "ardour/panner.h"
@@ -92,10 +95,7 @@ Route::Route (Session& sess, string name, PresentationInfo::Flag flag, DataType
        , Muteable (sess, name)
        , _active (true)
        , _signal_latency (0)
-       , _signal_latency_at_amp_position (0)
-       , _signal_latency_at_trim_position (0)
-       , _initial_delay (0)
-       , _roll_delay (0)
+       , _disk_io_point (DiskIOPreFader)
        , _pending_process_reorder (0)
        , _pending_signals (0)
        , _pending_declick (true)
@@ -109,10 +109,10 @@ Route::Route (Session& sess, string name, PresentationInfo::Flag flag, DataType
        , _have_internal_generator (false)
        , _default_type (default_type)
        , _track_number (0)
+       , _strict_io (false)
        , _in_configure_processors (false)
        , _initial_io_setup (false)
        , _in_sidechain_setup (false)
-       , _strict_io (false)
        , _custom_meter_position_noted (false)
        , _pinmgr_proxy (0)
        , _patch_selector_dialog (0)
@@ -192,12 +192,9 @@ Route::init ()
                _amp->set_display_name (_("Monitor"));
        }
 
-#if 0 // not used - just yet
        if (!is_master() && !is_monitor() && !is_auditioner()) {
-               _delayline.reset (new DelayLine (_session, _name));
-               add_processor (_delayline, PreFader);
+               _delayline.reset (new DelayLine (_session, name ()));
        }
-#endif
 
        /* and input trim */
 
@@ -290,7 +287,7 @@ Route::set_trim (gain_t val, Controllable::GroupControlDisposition /* group over
 }
 
 void
-Route::maybe_declick (BufferSet&, framecnt_t, int)
+Route::maybe_declick (BufferSet&, samplecnt_t, int)
 {
        /* this is the "bus" implementation and they never declick.
         */
@@ -300,56 +297,101 @@ Route::maybe_declick (BufferSet&, framecnt_t, int)
 /** Process this route for one (sub) cycle (process thread)
  *
  * @param bufs Scratch buffers to use for the signal path
- * @param start_frame Initial transport frame
- * @param end_frame Final transport frame
- * @param nframes Number of frames to output (to ports)
+ * @param start_sample Initial transport sample
+ * @param end_sample Final transport sample
+ * @param nframes Number of samples to output (to ports)
  *
- * Note that (end_frame - start_frame) may not be equal to nframes when the
+ * Note that (end_sample - start_sample) may not be equal to nframes when the
  * transport speed isn't 1.0 (eg varispeed).
  */
 void
 Route::process_output_buffers (BufferSet& bufs,
-                              framepos_t start_frame, framepos_t end_frame, pframes_t nframes,
-                              int declick, bool gain_automation_ok)
+                              samplepos_t start_sample, samplepos_t end_sample, pframes_t nframes,
+                              int declick, bool gain_automation_ok, bool run_disk_reader)
 {
        /* Caller must hold process lock */
        assert (!AudioEngine::instance()->process_lock().trylock());
 
        Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
        if (!lm.locked()) {
-               // can this actually happen? functions calling process_output_buffers()
-               // already take a reader-lock.
+               // can this actually happen?
+               // Places that need a WriterLock on (_processor_lock) must also take the process-lock.
                bufs.silence (nframes, 0);
+               assert (0); // ...one way to find out.
                return;
        }
 
-       automation_run (start_frame, nframes);
+       /* We should offset the route-owned ctrls by the given latency, however
+        * this only affects Mute. Other route-owned controls (solo, polarity..)
+        * are not automatable.
+        *
+        * Mute has its own issues since there's not a single mute-point,
+        * but in general
+        */
+       automation_run (start_sample, nframes);
 
        /* figure out if we're going to use gain automation */
        if (gain_automation_ok) {
                _amp->set_gain_automation_buffer (_session.gain_automation_buffer ());
                _amp->setup_gain_automation (
-                               start_frame + _signal_latency_at_amp_position,
-                               end_frame + _signal_latency_at_amp_position,
+                               start_sample + _amp->output_latency (),
+                               end_sample + _amp->output_latency (),
                                nframes);
 
                _trim->set_gain_automation_buffer (_session.trim_automation_buffer ());
                _trim->setup_gain_automation (
-                               start_frame + _signal_latency_at_trim_position,
-                               end_frame + _signal_latency_at_trim_position,
+                               start_sample + _trim->output_latency (),
+                               end_sample + _trim->output_latency (),
                                nframes);
-       } else {
-               _amp->apply_gain_automation (false);
-               _trim->apply_gain_automation (false);
        }
 
-       /* Tell main outs what to do about monitoring.  We do this so that
-          on a transition between monitoring states we get a de-clicking gain
-          change in the _main_outs delivery, if config.get_use_monitor_fades()
-          is true.
+       /* We align the playhead to output. The user hears what the clock says:
+        * When the playhead/clock says 1:00:00:00 the user will hear the audio sample
+        * at 1:00:00:00. sample_start will be [sample at] 1:00:00:00
+        *
+        * e.g. clock says Time T = 0,  sample_start = 0
+        * Disk-read(play) -> latent-plugin (+10) -> fader-automation -> output (+5)
+        * -> total playback latency "disk -> out" is 15.
+        * -> at Time T= -15, the disk-reader reads sample T=0.
+        * By the Time T=0 is reached (dt=15 later) that sample is audible.
+        */
 
-          We override this in the case where we have an internal generator.
-       */
+       start_sample += _signal_latency;
+       end_sample += _signal_latency;
+
+       start_sample += _output->latency ();
+       end_sample += _output->latency ();
+
+       /* Note: during intial pre-roll 'start_sample' as passed as argument can be negative.
+        * Functions calling process_output_buffers() will set  "run_disk_reader"
+        * to false if the pre-roll count-down is larger than playback_latency ().
+        *
+        * playback_latency() is guarnteed to be <= _signal_latency + _output->latency ()
+        */
+       assert (!_disk_reader || !run_disk_reader || start_sample >= 0);
+
+       /* however the disk-writer may need to pick up output from other tracks
+        * during pre-roll (in particular if this route has latent effects after the disk).
+        *
+        * e.g. track 1 play -> latency A --port--> track2 capture -> latency B ---> out
+        * total pre-roll = A + B.
+        *
+        * Note the disk-writer has built-in overlap detection (it's safe to run it early)
+        * given that
+        */
+       bool run_disk_writer = false;
+       if (_disk_writer) {
+               samplecnt_t latency_preroll = _session.remaining_latency_preroll ();
+               run_disk_writer = latency_preroll < nframes + (_signal_latency + _output->latency ());
+       }
+
+       /* Tell main outs what to do about monitoring.  We do this so that
+        * on a transition between monitoring states we get a de-clicking gain
+        * change in the _main_outs delivery, if config.get_use_monitor_fades()
+        * is true.
+        *
+        * We override this in the case where we have an internal generator.
+        */
        bool silence = _have_internal_generator ? false : (monitoring_state () == MonitoringSilence);
 
        _main_outs->no_outs_cuz_we_no_monitor (silence);
@@ -358,6 +400,8 @@ Route::process_output_buffers (BufferSet& bufs,
           GLOBAL DECLICK (for transport changes etc.)
           ----------------------------------------------------------------------------------------- */
 
+       // XXX not latency compensated. calls Amp::declick, but there may be
+       // plugins between disk and Fader.
        maybe_declick (bufs, nframes, declick);
        _pending_declick = 0;
 
@@ -365,6 +409,14 @@ Route::process_output_buffers (BufferSet& bufs,
           DENORMAL CONTROL/PHASE INVERT
           ----------------------------------------------------------------------------------------- */
 
+       /* TODO phase-control should become a processor, or rather a Stub-processor:
+        * a point in the chain which calls a special-cased private Route method.
+        * _phase_control is route-owned and dynamic.)
+        * and we should rename it to polarity.
+        *
+        * denormals: we'll need to protect silent inputs as well as silent disk
+        * (when not monitoring input).  Or simply drop that feature.
+        */
        if (!_phase_control->none()) {
 
                int chn = 0;
@@ -409,8 +461,8 @@ Route::process_output_buffers (BufferSet& bufs,
                                        sp[nx] += 1.0e-27f;
                                }
                        }
-
                }
+
        }
 
        /* -------------------------------------------------------------------------------------------
@@ -420,11 +472,17 @@ Route::process_output_buffers (BufferSet& bufs,
        /* set this to be true if the meter will already have been ::run() earlier */
        bool const meter_already_run = metering_state() == MeteringInput;
 
-       framecnt_t latency = 0;
-       const double speed = _session.transport_speed ();
+       samplecnt_t latency = 0;
+       const double speed = (is_auditioner() ? 1.0 : _session.transport_speed ());
 
        for (ProcessorList::const_iterator i = _processors.begin(); i != _processors.end(); ++i) {
 
+               /* TODO check for split cycles here.
+                *
+                * start_frame, end_frame is adjusted by latency and may
+                * cross loop points.
+                */
+
                if (meter_already_run && boost::dynamic_pointer_cast<PeakMeter> (*i)) {
                        /* don't ::run() the meter, otherwise it will have its previous peak corrupted */
                        continue;
@@ -444,31 +502,60 @@ Route::process_output_buffers (BufferSet& bufs,
                }
 #endif
 
-               /* should we NOT run plugins here if the route is inactive?
-                  do we catch route != active somewhere higher?
-               */
-
                if (boost::dynamic_pointer_cast<Send>(*i) != 0) {
-                       boost::dynamic_pointer_cast<Send>(*i)->set_delay_in(_signal_latency - latency);
+                       // inform the reader that we're sending a late signal,
+                       // relative to original (output aligned) start_sample
+                       boost::dynamic_pointer_cast<Send>(*i)->set_delay_in (latency);
                }
                if (boost::dynamic_pointer_cast<PluginInsert>(*i) != 0) {
-                       const framecnt_t longest_session_latency = _initial_delay + _signal_latency;
+                       /* set potential sidechain ports, capture and playback latency.
+                        * This effectively sets jack port latency which should include
+                        * up/downstream latencies.
+                        *
+                        * However, the value is not used by Ardour (2017-09-20) and calling
+                        * IO::latency() is expensive, so we punt.
+                        *
+                        * capture should be
+                        *      input()->latenct + latency,
+                        * playback should be
+                        *      output->latency() + _signal_latency - latency
+                        *
+                        * Also see note below, _signal_latency may be smaller than latency
+                        * if a plugin's latency increases while it's running.
+                        */
+                       const samplecnt_t playback_latency = std::max ((samplecnt_t)0, _signal_latency - latency);
                        boost::dynamic_pointer_cast<PluginInsert>(*i)->set_sidechain_latency (
-                                       _initial_delay + latency, longest_session_latency - latency);
+                                       /* input->latency() + */ latency, /* output->latency() + */ playback_latency);
+               }
+
+               double pspeed = speed;
+               if ((!run_disk_reader && (*i) == _disk_reader) || (!run_disk_writer && (*i) == _disk_writer)) {
+                       /* run with speed 0, no-roll */
+                       pspeed = 0;
                }
 
-               //cerr << name() << " run " << (*i)->name() << endl;
-               (*i)->run (bufs, start_frame - latency, end_frame - latency, speed, nframes, *i != _processors.back());
+               (*i)->run (bufs, start_sample - latency, end_sample - latency, pspeed, nframes, *i != _processors.back());
                bufs.set_count ((*i)->output_streams());
 
+               /* Note: plugin latency may change. While the plugin does inform the session via
+                * processor_latency_changed(). But the session may not yet have gotten around to
+                * update the actual worste-case and update this track's _signal_latency.
+                *
+                * So there can be cases where adding up all latencies may not equal _signal_latency.
+                */
                if ((*i)->active ()) {
                        latency += (*i)->signal_latency ();
                }
+#if 0
+               if ((*i) == _delayline) {
+                       latency += _delayline->get_delay ();
+               }
+#endif
        }
 }
 
 void
-Route::bounce_process (BufferSet& buffers, framepos_t start, framecnt_t nframes,
+Route::bounce_process (BufferSet& buffers, samplepos_t start, samplecnt_t nframes,
                boost::shared_ptr<Processor> endpoint,
                bool include_endpoint, bool for_export, bool for_freeze)
 {
@@ -477,7 +564,7 @@ Route::bounce_process (BufferSet& buffers, framepos_t start, framecnt_t nframes,
                return;
        }
 
-       framecnt_t latency = bounce_get_latency(_amp, false, for_export, for_freeze);
+       samplecnt_t latency = bounce_get_latency(_amp, false, for_export, for_freeze);
        _amp->set_gain_automation_buffer (_session.gain_automation_buffer ());
        _amp->setup_gain_automation (start - latency, start - latency + nframes, nframes);
 
@@ -528,11 +615,11 @@ Route::bounce_process (BufferSet& buffers, framepos_t start, framecnt_t nframes,
        }
 }
 
-framecnt_t
+samplecnt_t
 Route::bounce_get_latency (boost::shared_ptr<Processor> endpoint,
                bool include_endpoint, bool for_export, bool for_freeze) const
 {
-       framecnt_t latency = 0;
+       samplecnt_t latency = 0;
        if (!endpoint && !include_endpoint) {
                return latency;
        }
@@ -592,16 +679,16 @@ Route::n_process_buffers ()
 }
 
 void
-Route::monitor_run (framepos_t start_frame, framepos_t end_frame, pframes_t nframes, int declick)
+Route::monitor_run (samplepos_t start_sample, samplepos_t end_sample, pframes_t nframes, int declick)
 {
        assert (is_monitor());
        BufferSet& bufs (_session.get_route_buffers (n_process_buffers()));
        fill_buffers_with_input (bufs, _input, nframes);
-       passthru (bufs, start_frame, end_frame, nframes, declick);
+       passthru (bufs, start_sample, end_sample, nframes, declick, true, false);
 }
 
 void
-Route::passthru (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, int declick)
+Route::passthru (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_sample, pframes_t nframes, int declick, bool gain_automation_ok, bool run_disk_reader)
 {
        _silent = false;
 
@@ -615,18 +702,23 @@ Route::passthru (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame,
                bufs.silence (nframes, 0);
        }
 
-       write_out_of_band_data (bufs, start_frame, end_frame, nframes);
-       process_output_buffers (bufs, start_frame, end_frame, nframes, declick, true);
+       /* append immediate messages to the first MIDI buffer (thus sending it to the first output port) */
+
+       write_out_of_band_data (bufs, start_sample, end_sample, nframes);
+
+       /* run processor chain */
+
+       process_output_buffers (bufs, start_sample, end_sample, nframes, declick, gain_automation_ok, run_disk_reader);
 }
 
 void
-Route::passthru_silence (framepos_t start_frame, framepos_t end_frame, pframes_t nframes, int declick)
+Route::passthru_silence (samplepos_t start_sample, samplepos_t end_sample, pframes_t nframes, int declick)
 {
        BufferSet& bufs (_session.get_route_buffers (n_process_buffers(), true));
 
        bufs.set_count (_input->n_ports());
-       write_out_of_band_data (bufs, start_frame, end_frame, nframes);
-       process_output_buffers (bufs, start_frame, end_frame, nframes, declick, false);
+       write_out_of_band_data (bufs, start_sample, end_sample, nframes);
+       process_output_buffers (bufs, start_sample, end_sample, nframes, declick, false, false);
 }
 
 void
@@ -1248,7 +1340,7 @@ Route::clear_processors (Placement p)
                                seen_amp = true;
                        }
 
-                       if ((*i) == _amp || (*i) == _meter || (*i) == _main_outs || (*i) == _delayline || (*i) == _trim) {
+                       if (is_internal_processor (*i)) {
 
                                /* you can't remove these */
 
@@ -1298,6 +1390,15 @@ Route::clear_processors (Placement p)
        }
 }
 
+bool
+Route::is_internal_processor (boost::shared_ptr<Processor> p) const
+{
+       if (p == _amp || p == _meter || p == _main_outs || p == _delayline || p == _trim) {
+               return true;
+       }
+       return false;
+}
+
 int
 Route::remove_processor (boost::shared_ptr<Processor> processor, ProcessorStreams* err, bool need_process_lock)
 {
@@ -1317,7 +1418,7 @@ Route::remove_processor (boost::shared_ptr<Processor> processor, ProcessorStream
 
        /* these can never be removed */
 
-       if (processor == _amp || processor == _meter || processor == _main_outs || processor == _delayline || processor == _trim) {
+       if (is_internal_processor (processor)) {
                return 0;
        }
 
@@ -1419,11 +1520,11 @@ int
 Route::replace_processor (boost::shared_ptr<Processor> old, boost::shared_ptr<Processor> sub, ProcessorStreams* err)
 {
        /* these can never be removed */
-       if (old == _amp || old == _meter || old == _main_outs || old == _delayline || old == _trim) {
+       if (is_internal_processor (old)) {
                return 1;
        }
        /* and can't be used as substitute, either */
-       if (sub == _amp || sub == _meter || sub == _main_outs || sub == _delayline || sub == _trim) {
+       if (is_internal_processor (sub)) {
                return 1;
        }
 
@@ -1538,7 +1639,7 @@ Route::remove_processors (const ProcessorList& to_be_deleted, ProcessorStreams*
 
                        /* these can never be removed */
 
-                       if (processor == _amp || processor == _meter || processor == _main_outs || processor == _delayline || processor == _trim) {
+                       if (is_internal_processor (processor)) {
                                ++i;
                                continue;
                        }
@@ -1806,8 +1907,6 @@ Route::configure_processors_unlocked (ProcessorStreams* err, Glib::Threads::RWLo
        // TODO check for a potential ReaderLock after ReaderLock ??
        Glib::Threads::RWLock::ReaderLock lr (_processor_lock);
 
-       framecnt_t chain_latency = _input->latency ();
-
        list< pair<ChanCount,ChanCount> >::iterator c = configuration.begin();
        for (ProcessorList::iterator p = _processors.begin(); p != _processors.end(); ++p, ++c) {
 
@@ -1819,9 +1918,6 @@ Route::configure_processors_unlocked (ProcessorStreams* err, Glib::Threads::RWLo
                        return -1;
                }
 
-               (*p)->set_input_latency (chain_latency);
-               chain_latency += (*p)->signal_latency ();
-
                processor_max_streams = ChanCount::max(processor_max_streams, c->first);
                processor_max_streams = ChanCount::max(processor_max_streams, c->second);
 
@@ -2101,6 +2197,11 @@ Route::reorder_processors (const ProcessorList& new_order, ProcessorStreams* err
                g_atomic_int_set (&_pending_process_reorder, 1);
        }
 
+       /* update processor input/output latency
+        * (total signal_latency does not change)
+        */
+       update_signal_latency (true);
+
        return 0;
 }
 
@@ -2326,21 +2427,22 @@ Route::state(bool full_state)
        XMLNode *node = new XMLNode("Route");
        ProcessorList::iterator i;
 
-       node->set_property ("id", id ());
-       node->set_property ("name", name());
-       node->set_property ("default-type", _default_type);
-       node->set_property ("strict-io", _strict_io);
+       node->set_property (X_("id"), id ());
+       node->set_property (X_("name"), name());
+       node->set_property (X_("default-type"), _default_type);
+       node->set_property (X_("strict-io"), _strict_io);
 
        node->add_child_nocopy (_presentation_info.get_state());
 
-       node->set_property ("active", _active);
-       node->set_property ("denormal-protection", _denormal_protection);
-       node->set_property ("meter-point", _meter_point);
+       node->set_property (X_("active"), _active);
+       node->set_property (X_("denormal-protection"), _denormal_protection);
+       node->set_property (X_("meter-point"), _meter_point);
+       node->set_property (X_("disk-io-point"), _disk_io_point);
 
-       node->set_property ("meter-type", _meter_type);
+       node->set_property (X_("meter-type"), _meter_type);
 
        if (_route_group) {
-               node->set_property ("route-group", _route_group->name());
+               node->set_property (X_("route-group"), _route_group->name());
        }
 
        node->add_child_nocopy (_solo_control->get_state ());
@@ -2370,6 +2472,9 @@ Route::state(bool full_state)
        {
                Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
                for (i = _processors.begin(); i != _processors.end(); ++i) {
+                       if (*i == _delayline) {
+                               continue;
+                       }
                        if (!full_state) {
                                /* template save: do not include internal sends functioning as
                                         aux sends because the chance of the target ID
@@ -2492,6 +2597,17 @@ Route::set_state (const XMLNode& node, int version)
                }
        }
 
+       DiskIOPoint diop;
+       if (node.get_property (X_("disk-io-point"), diop)) {
+               if (_disk_writer) {
+                       _disk_writer->set_display_to_user (diop == DiskIOCustom);
+               }
+               if (_disk_reader) {
+                       _disk_reader->set_display_to_user (diop == DiskIOCustom);
+               }
+               set_disk_io_point (diop);
+       }
+
        node.get_property (X_("meter-type"), _meter_type);
 
        _initial_io_setup = false;
@@ -2575,6 +2691,10 @@ Route::set_state (const XMLNode& node, int version)
                }
        }
 
+       if (_delayline) {
+               _delayline->set_name (name ());
+       }
+
        return 0;
 }
 
@@ -2810,10 +2930,7 @@ Route::set_processor_state (const XMLNode& node)
                        _meter->set_state (**niter, Stateful::current_state_version);
                        new_order.push_back (_meter);
                } else if (prop->value() == "delay") {
-                       if (_delayline) {
-                               _delayline->set_state (**niter, Stateful::current_state_version);
-                               new_order.push_back (_delayline);
-                       }
+                       // skip -- internal
                } else if (prop->value() == "main-outs") {
                        _main_outs->set_state (**niter, Stateful::current_state_version);
                } else if (prop->value() == "intreturn") {
@@ -2831,6 +2948,12 @@ Route::set_processor_state (const XMLNode& node)
                } else if (prop->value() == "capture") {
                        /* CapturingProcessor should never be restored, it's always
                           added explicitly when needed */
+               } else if (prop->value() == "diskreader" && _disk_reader) {
+                       _disk_reader->set_state (**niter, Stateful::current_state_version);
+                       new_order.push_back (_disk_reader);
+               } else if (prop->value() == "diskwriter" && _disk_writer) {
+                       _disk_writer->set_state (**niter, Stateful::current_state_version);
+                       new_order.push_back (_disk_writer);
                } else {
                        set_processor_state (**niter, prop, new_order, must_configure);
                }
@@ -2969,7 +3092,7 @@ Route::curve_reallocate ()
 }
 
 void
-Route::silence (framecnt_t nframes)
+Route::silence (samplecnt_t nframes)
 {
        Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
        if (!lm.locked()) {
@@ -2980,11 +3103,11 @@ Route::silence (framecnt_t nframes)
 }
 
 void
-Route::silence_unlocked (framecnt_t nframes)
+Route::silence_unlocked (samplecnt_t nframes)
 {
        /* Must be called with the processor lock held */
 
-       const framepos_t now = _session.transport_frame ();
+       const samplepos_t now = _session.transport_sample ();
 
        if (!_silent) {
 
@@ -3314,24 +3437,20 @@ Route::feeds_according_to_graph (boost::shared_ptr<Route> other)
 
 /** Called from the (non-realtime) butler thread when the transport is stopped */
 void
-Route::non_realtime_transport_stop (framepos_t now, bool flush)
+Route::non_realtime_transport_stop (samplepos_t now, bool flush)
 {
-       {
-               Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
-
-               Automatable::non_realtime_transport_stop (now, flush);
+       Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
 
-               for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
+       Automatable::non_realtime_transport_stop (now, flush);
 
-                       if (!_have_internal_generator && (Config->get_plugins_stop_with_transport() && flush)) {
-                               (*i)->flush ();
-                       }
+       for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
 
-                       (*i)->non_realtime_transport_stop (now, flush);
+               if (!_have_internal_generator && (Config->get_plugins_stop_with_transport() && flush)) {
+                       (*i)->flush ();
                }
-       }
 
-       _roll_delay = _initial_delay;
+               (*i)->non_realtime_transport_stop (now, flush);
+       }
 }
 
 void
@@ -3508,7 +3627,7 @@ Route::pans_required () const
 }
 
 void
-Route::flush_processor_buffers_locked (framecnt_t nframes)
+Route::flush_processor_buffers_locked (samplecnt_t nframes)
 {
        for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
                boost::shared_ptr<Delivery> d = boost::dynamic_pointer_cast<Delivery> (*i);
@@ -3524,7 +3643,7 @@ Route::flush_processor_buffers_locked (framecnt_t nframes)
 }
 
 int
-Route::no_roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame, bool session_state_changing)
+Route::no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool session_state_changing)
 {
        Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
 
@@ -3552,53 +3671,136 @@ Route::no_roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame,
                */
        }
 
+       no_roll_unlocked (nframes, start_sample, end_sample);
+
+       return 0;
+}
+
+void
+Route::no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample)
+{
        BufferSet& bufs = _session.get_route_buffers (n_process_buffers());
 
        fill_buffers_with_input (bufs, _input, nframes);
 
+       /* filter captured data before meter sees it */
+       filter_input (bufs);
+
        if (_meter_point == MeterInput) {
-               _meter->run (bufs, start_frame, end_frame, 0.0, nframes, true);
+               _meter->run (bufs, start_sample, end_sample, 0.0, nframes, true);
        }
 
-       _amp->apply_gain_automation (false);
-       _trim->apply_gain_automation (false);
-       passthru (bufs, start_frame, end_frame, nframes, 0);
+       passthru (bufs, start_sample, end_sample, nframes, 0, true, false);
 
        flush_processor_buffers_locked (nframes);
+}
 
-       return 0;
+samplecnt_t
+Route::playback_latency (bool incl_downstream) const
+{
+       samplecnt_t rv;
+       if (_disk_reader) {
+               rv = _disk_reader->output_latency ();
+       } else {
+               rv = _signal_latency;
+       }
+       if (incl_downstream) {
+               rv += _output->connected_latency (true);
+       } else {
+               rv += _output->latency ();
+       }
+       return rv;
+}
+
+pframes_t
+Route::latency_preroll (pframes_t nframes, samplepos_t& start_sample, samplepos_t& end_sample)
+{
+       samplecnt_t latency_preroll = _session.remaining_latency_preroll ();
+       if (latency_preroll == 0) {
+               return nframes;
+       }
+       if (!_disk_reader) {
+               start_sample -= latency_preroll;
+               end_sample   -= latency_preroll;
+               return nframes;
+       }
+
+       samplecnt_t route_offset = playback_latency ();
+
+       if (latency_preroll > route_offset + nframes) {
+               no_roll_unlocked (nframes, start_sample - latency_preroll, end_sample - latency_preroll);
+               return 0;
+       }
+
+       if (latency_preroll > route_offset) {
+
+               samplecnt_t skip = latency_preroll - route_offset;
+               no_roll_unlocked (skip, start_sample - latency_preroll, start_sample - latency_preroll + skip);
+
+               if (nframes == skip) {
+                       return 0;
+               }
+
+               Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
+               for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
+                       boost::shared_ptr<IOProcessor> iop = boost::dynamic_pointer_cast<IOProcessor> (*i);
+                       if (iop) {
+                               iop->increment_port_buffer_offset (skip);
+                       }
+               }
+               _input->increment_port_buffer_offset (skip);
+               _output->increment_port_buffer_offset (skip);
+
+               start_sample -= route_offset;
+               end_sample -= route_offset;
+
+               return nframes - skip;
+       }
+
+       start_sample -= latency_preroll;
+       end_sample -= latency_preroll;
+       return nframes;
 }
 
 int
-Route::roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame, int declick, bool& /* need_butler */)
+Route::roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, int declick, bool& need_butler)
 {
        Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
+
        if (!lm.locked()) {
                return 0;
        }
 
        if (!_active) {
                silence_unlocked (nframes);
+               if (_meter_point == MeterInput && ((_monitoring_control->monitoring_choice() & MonitorInput) || (!_disk_writer || _disk_writer->record_enabled()))) {
+                       _meter->reset();
+               }
                return 0;
        }
-
-       framepos_t unused = 0;
-
-       if ((nframes = check_initial_delay (nframes, unused)) == 0) {
+       if ((nframes = latency_preroll (nframes, start_sample, end_sample)) == 0) {
                return 0;
        }
 
        _silent = false;
 
-       BufferSet& bufs = _session.get_route_buffers (n_process_buffers());
+       BufferSet& bufs = _session.get_route_buffers (n_process_buffers ());
 
        fill_buffers_with_input (bufs, _input, nframes);
 
-       if (_meter_point == MeterInput) {
-               _meter->run (bufs, start_frame, end_frame, 1.0, nframes, true);
+       /* filter captured data before meter sees it */
+       filter_input (bufs);
+
+       if (_meter_point == MeterInput &&
+           ((_monitoring_control->monitoring_choice() & MonitorInput) || (_disk_writer && _disk_writer->record_enabled()))) {
+               _meter->run (bufs, start_sample, end_sample, 1.0 /*speed()*/, nframes, true);
        }
 
-       passthru (bufs, start_frame, end_frame, nframes, declick);
+       passthru (bufs, start_sample, end_sample, nframes, declick, (!_disk_writer || !_disk_writer->record_enabled()) && _session.transport_rolling(), true);
+
+       if ((_disk_reader && _disk_reader->need_butler()) || (_disk_writer && _disk_writer->need_butler())) {
+               need_butler = true;
+       }
 
        flush_processor_buffers_locked (nframes);
 
@@ -3606,7 +3808,7 @@ Route::roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame, in
 }
 
 int
-Route::silent_roll (pframes_t nframes, framepos_t /*start_frame*/, framepos_t /*end_frame*/, bool& /* need_butler */)
+Route::silent_roll (pframes_t nframes, samplepos_t /*start_sample*/, samplepos_t /*end_sample*/, bool& /* need_butler */)
 {
        silence (nframes);
        flush_processor_buffers_locked (nframes);
@@ -3658,6 +3860,10 @@ Route::apply_processor_changes_rt ()
        }
        if (changed) {
                set_processor_positions ();
+               /* update processor input/output latency
+                * (total signal_latency does not change)
+                */
+               update_signal_latency (true);
        }
        if (emissions != 0) {
                g_atomic_int_set (&_pending_signals, emissions);
@@ -3829,53 +4035,54 @@ Route::add_export_point()
                Glib::Threads::Mutex::Lock lx (AudioEngine::instance()->process_lock ());
                Glib::Threads::RWLock::WriterLock lw (_processor_lock);
 
-               // this aligns all tracks; but not tracks + busses
-               assert (_session.worst_track_latency () >= _initial_delay);
-               _capturing_processor.reset (new CapturingProcessor (_session, _session.worst_track_latency () - _initial_delay));
-               _capturing_processor->activate ();
-
+               /* Align all tracks for stem-export w/o processing.
+                * Compensate for all plugins between the this route's disk-reader
+                * and the common final downstream output (ie alignment point for playback).
+                */
+               _capturing_processor.reset (new CapturingProcessor (_session, playback_latency (true)));
                configure_processors_unlocked (0, &lw);
-
+               _capturing_processor->activate ();
        }
 
        return _capturing_processor;
 }
 
-framecnt_t
-Route::update_signal_latency ()
+samplecnt_t
+Route::update_signal_latency (bool apply_to_delayline)
 {
-       framecnt_t l = _output->user_latency();
-       framecnt_t lamp = 0;
-       bool before_amp = true;
-       framecnt_t ltrim = 0;
-       bool before_trim = true;
+       Glib::Threads::RWLock::ReaderLock lm (_processor_lock);
 
-       for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
+       samplecnt_t l_in  = 0; // _input->latency ();
+       samplecnt_t l_out = _output->user_latency();
+       for (ProcessorList::reverse_iterator i = _processors.rbegin(); i != _processors.rend(); ++i) {
+               (*i)->set_output_latency (l_out);
                if ((*i)->active ()) {
-                       l += (*i)->signal_latency ();
-               }
-               if ((*i) == _amp) {
-                       before_amp = false;
-               }
-               if ((*i) == _trim) {
-                       before_amp = false;
-               }
-               if (before_amp) {
-                       lamp = l;
+                       l_out += (*i)->signal_latency ();
                }
-               if (before_trim) {
-                       lamp = l;
+       }
+
+       DEBUG_TRACE (DEBUG::Latency, string_compose ("%1: internal signal latency = %2\n", _name, l_out));
+
+       _signal_latency = l_out;
+
+       for (ProcessorList::iterator i = _processors.begin(); i != _processors.end(); ++i) {
+               if ((*i)->active ()) {
+                       l_in += (*i)->signal_latency ();
                }
+               (*i)->set_input_latency (l_in);
+               (*i)->set_playback_offset (_signal_latency + _output->latency ());
+               (*i)->set_capture_offset (_input->latency ());
        }
 
-       DEBUG_TRACE (DEBUG::Latency, string_compose ("%1: internal signal latency = %2\n", _name, l));
 
-       // TODO: (lamp - _signal_latency) to sync to output (read-ahed),  currently _roll_delay shifts this around
-       _signal_latency_at_amp_position = lamp;
-       _signal_latency_at_trim_position = ltrim;
+       lm.release ();
+
+       if (apply_to_delayline) {
+               /* see also Session::post_playback_latency() */
+               apply_latency_compensation ();
+       }
 
-       if (_signal_latency != l) {
-               _signal_latency = l;
+       if (_signal_latency != l_out) {
                signal_latency_changed (); /* EMIT SIGNAL */
        }
 
@@ -3883,34 +4090,35 @@ Route::update_signal_latency ()
 }
 
 void
-Route::set_user_latency (framecnt_t nframes)
+Route::set_user_latency (samplecnt_t nframes)
 {
        _output->set_user_latency (nframes);
        _session.update_latency_compensation ();
 }
 
 void
-Route::set_latency_compensation (framecnt_t longest_session_latency)
+Route::apply_latency_compensation ()
 {
-       framecnt_t old = _initial_delay;
+       if (_delayline) {
+               samplecnt_t old = _delayline->get_delay ();
 
-       if (_signal_latency < longest_session_latency) {
-               _initial_delay = longest_session_latency - _signal_latency;
-       } else {
-               _initial_delay = 0;
-       }
+               samplecnt_t play_lat_in = _input->connected_latency (true);
+               samplecnt_t play_lat_out = _output->connected_latency (true);
+               samplecnt_t latcomp = play_lat_in - play_lat_out - _signal_latency;
 
-       DEBUG_TRACE (DEBUG::Latency, string_compose (
-                            "%1: compensate for maximum latency of %2,"
-                            "given own latency of %3, using initial delay of %4\n",
-                            name(), longest_session_latency, _signal_latency, _initial_delay));
+#if 0 // DEBUG
+               samplecnt_t capt_lat_in = _input->connected_latency (false);
+               samplecnt_t capt_lat_out = _output->connected_latency (false);
+               samplecnt_t latcomp_capt = capt_lat_out - capt_lat_in - _signal_latency;
 
-       if (_initial_delay != old) {
-               initial_delay_changed (); /* EMIT SIGNAL */
-       }
+               cout << "ROUTE " << name() << " delay for " << latcomp << " (c: " << latcomp_capt << ")" << endl;
+#endif
+
+               _delayline->set_delay (latcomp > 0 ? latcomp : 0);
 
-       if (_session.transport_stopped()) {
-               _roll_delay = _initial_delay;
+               if (old !=  _delayline->get_delay ()) {
+                       signal_latency_updated (); /* EMIT SIGNAL */
+               }
        }
 }
 
@@ -3951,18 +4159,18 @@ Route::set_pending_declick (int declick)
  *  Adds undo commands for any shifts that are performed.
  *
  * @param pos Position to start shifting from.
- * @param frames Amount to shift forwards by.
+ * @param samples Amount to shift forwards by.
  */
 
 void
-Route::shift (framepos_t pos, framecnt_t frames)
+Route::shift (samplepos_t pos, samplecnt_t samples)
 {
        /* gain automation */
        {
                boost::shared_ptr<AutomationControl> gc = _amp->gain_control();
 
                XMLNode &before = gc->alist()->get_state ();
-               gc->alist()->shift (pos, frames);
+               gc->alist()->shift (pos, samples);
                XMLNode &after = gc->alist()->get_state ();
                _session.add_command (new MementoCommand<AutomationList> (*gc->alist().get(), &before, &after));
        }
@@ -3972,7 +4180,7 @@ Route::shift (framepos_t pos, framecnt_t frames)
                boost::shared_ptr<AutomationControl> gc = _trim->gain_control();
 
                XMLNode &before = gc->alist()->get_state ();
-               gc->alist()->shift (pos, frames);
+               gc->alist()->shift (pos, samples);
                XMLNode &after = gc->alist()->get_state ();
                _session.add_command (new MementoCommand<AutomationList> (*gc->alist().get(), &before, &after));
        }
@@ -3988,7 +4196,7 @@ Route::shift (framepos_t pos, framecnt_t frames)
                        if (pc) {
                                boost::shared_ptr<AutomationList> al = pc->alist();
                                XMLNode& before = al->get_state ();
-                               al->shift (pos, frames);
+                               al->shift (pos, samples);
                                XMLNode& after = al->get_state ();
                                _session.add_command (new MementoCommand<AutomationList> (*al.get(), &before, &after));
                        }
@@ -4007,7 +4215,7 @@ Route::shift (framepos_t pos, framecnt_t frames)
                                if (ac) {
                                        boost::shared_ptr<AutomationList> al = ac->alist();
                                        XMLNode &before = al->get_state ();
-                                       al->shift (pos, frames);
+                                       al->shift (pos, samples);
                                        XMLNode &after = al->get_state ();
                                        _session.add_command (new MementoCommand<AutomationList> (*al.get(), &before, &after));
                                }
@@ -4375,8 +4583,8 @@ Route::unknown_processors () const
 }
 
 
-framecnt_t
-Route::update_port_latencies (PortSet& from, PortSet& to, bool playback, framecnt_t our_latency) const
+samplecnt_t
+Route::update_port_latencies (PortSet& from, PortSet& to, bool playback, samplecnt_t our_latency) const
 {
        /* we assume that all our input ports feed all our output ports. its not
           universally true, but the alternative is way too corner-case to worry about.
@@ -4424,10 +4632,10 @@ Route::update_port_latencies (PortSet& from, PortSet& to, bool playback, framecn
        return all_connections.max;
 }
 
-framecnt_t
+samplecnt_t
 Route::set_private_port_latencies (bool playback) const
 {
-       framecnt_t own_latency = 0;
+       samplecnt_t own_latency = 0;
 
        /* Processor list not protected by lock: MUST BE CALLED FROM PROCESS THREAD
           OR LATENCY CALLBACK.
@@ -4456,7 +4664,7 @@ Route::set_private_port_latencies (bool playback) const
 }
 
 void
-Route::set_public_port_latencies (framecnt_t value, bool playback) const
+Route::set_public_port_latencies (samplecnt_t value, bool playback) const
 {
        /* this is called to set the JACK-visible port latencies, which take
           latency compensation into account.
@@ -4507,6 +4715,8 @@ Route::setup_invisible_processors ()
         */
 
        ProcessorList new_processors;
+       ProcessorList::iterator dr;
+       ProcessorList::iterator dw;
 
        /* find visible processors */
 
@@ -4611,12 +4821,6 @@ Route::setup_invisible_processors ()
                }
        }
 
-#if 0 // not used - just yet
-       if (!is_master() && !is_monitor() && !is_auditioner()) {
-               new_processors.push_front (_delayline);
-       }
-#endif
-
        /* MONITOR CONTROL */
 
        if (_monitor_control && is_monitor ()) {
@@ -4626,9 +4830,12 @@ Route::setup_invisible_processors ()
 
        /* TRIM CONTROL */
 
-       if (_trim && _trim->active()) {
+       ProcessorList::iterator trim = new_processors.end();
+
+       if (_trim->active()) {
                assert (!_trim->display_to_user ());
                new_processors.push_front (_trim);
+               trim = new_processors.begin();
        }
 
        /* INTERNAL RETURN */
@@ -4642,14 +4849,80 @@ Route::setup_invisible_processors ()
                new_processors.push_front (_intreturn);
        }
 
-       /* EXPORT PROCESSOR */
+       /* DISK READER & WRITER (for Track objects) */
+
+       if (_disk_reader || _disk_writer) {
+               switch (_disk_io_point) {
+               case DiskIOPreFader:
+                       if (trim != new_processors.end()) {
+                               /* insert BEFORE TRIM */
+                               if (_disk_writer) {
+                                       new_processors.insert (trim, _disk_writer);
+                               }
+                               if (_disk_reader) {
+                                       new_processors.insert (trim, _disk_reader);
+                               }
+                       } else {
+                               if (_disk_writer) {
+                                       new_processors.push_front (_disk_writer);
+                               }
+                               if (_disk_reader) {
+                                       new_processors.push_front (_disk_reader);
+                               }
+                       }
+                       break;
+               case DiskIOPostFader:
+                       /* insert BEFORE main outs */
+                       if (_disk_writer) {
+                               new_processors.insert (main, _disk_writer);
+                       }
+                       if (_disk_reader) {
+                               new_processors.insert (main, _disk_reader);
+                       }
+                       break;
+               case DiskIOCustom:
+                       /* reader and writer are visible under this condition, so they
+                        * are not invisible and thus not handled here.
+                        */
+                       break;
+               }
+       }
+
+       /* ensure dist-writer is before disk-reader */
+       if (_disk_reader && _disk_writer) {
+               ProcessorList::iterator reader_pos = find (new_processors.begin(), new_processors.end(), _disk_reader);
+               ProcessorList::iterator writer_pos = find (new_processors.begin(), new_processors.end(), _disk_writer);
+               assert (reader_pos != new_processors.end ());
+               assert (writer_pos != new_processors.end ());
+               if (std::distance (new_processors.begin(), reader_pos) < std::distance (new_processors.begin(), writer_pos)) {
+                       new_processors.erase (reader_pos);
+                       assert (writer_pos == find (new_processors.begin(), new_processors.end(), _disk_writer));
+                       new_processors.insert (++writer_pos, _disk_reader);
+               }
+       }
 
+
+       /* EXPORT PROCESSOR */
        if (_capturing_processor) {
                assert (!_capturing_processor->display_to_user ());
-               new_processors.push_front (_capturing_processor);
+               ProcessorList::iterator reader_pos = find (new_processors.begin(), new_processors.end(), _disk_reader);
+               if (reader_pos != new_processors.end()) {
+                       /* insert after disk-reader */
+                       new_processors.insert (++reader_pos, _capturing_processor);
+               } else {
+                       new_processors.push_front (_capturing_processor);
+               }
        }
 
-       setup_invisible_processors_oh_children_of_mine (new_processors);
+       if (!is_master() && !is_monitor() && !is_auditioner()) {
+               ProcessorList::iterator reader_pos = find (new_processors.begin(), new_processors.end(), _disk_reader);
+               if (reader_pos != new_processors.end()) {
+                       /* insert before disk-reader */
+                       new_processors.insert (reader_pos, _delayline);
+               } else {
+                       new_processors.push_front (_delayline);
+               }
+       }
 
        _processors = new_processors;
 
@@ -4737,15 +5010,6 @@ Route::processor_by_id (PBD::ID id) const
        return boost::shared_ptr<Processor> ();
 }
 
-/** @return the monitoring state, or in other words what data we are pushing
- *  into the route (data from the inputs, data from disk or silence)
- */
-MonitorState
-Route::monitoring_state () const
-{
-       return MonitoringInput;
-}
-
 /** @return what we should be metering; either the data coming from the input
  *  IO or the data that is flowing through the route.
  */
@@ -4794,7 +5058,7 @@ Route::the_instrument_unlocked () const
 
 
 void
-Route::non_realtime_locate (framepos_t pos)
+Route::non_realtime_locate (samplepos_t pos)
 {
        Automatable::non_realtime_locate (pos);
 
@@ -4802,9 +5066,11 @@ Route::non_realtime_locate (framepos_t pos)
                _pannable->non_realtime_locate (pos);
        }
 
-       if (_delayline.get()) {
-               _delayline.get()->flush();
+#if 0 // XXX mayhaps clear delayline here (and at stop?)
+       if (_delayline) {
+               _delayline->flush ();
        }
+#endif
 
        {
                //Glib::Threads::Mutex::Lock lx (AudioEngine::instance()->process_lock ());
@@ -4814,7 +5080,6 @@ Route::non_realtime_locate (framepos_t pos)
                        (*i)->non_realtime_locate (pos);
                }
        }
-       _roll_delay = _initial_delay;
 }
 
 void
@@ -5561,3 +5826,189 @@ Route::slavables () const
        rv.push_back (_solo_control);
        return rv;
 }
+
+void
+Route::set_disk_io_point (DiskIOPoint diop)
+{
+       bool display = false;
+
+       cerr << "set disk io to " << enum_2_string (diop) << endl;
+
+       switch (diop) {
+       case DiskIOCustom:
+               display = true;
+               break;
+       default:
+               display = false;
+       }
+
+       if (_disk_writer) {
+               _disk_writer->set_display_to_user (display);
+       }
+
+       if (_disk_reader) {
+               _disk_reader->set_display_to_user (display);
+       }
+
+       const bool changed = (diop != _disk_io_point);
+
+       _disk_io_point = diop;
+
+       if (changed) {
+               Glib::Threads::Mutex::Lock lx (AudioEngine::instance()->process_lock ());
+               configure_processors (0);
+       }
+
+       processors_changed (RouteProcessorChange ()); /* EMIT SIGNAL */
+}
+
+#ifdef USE_TRACKS_CODE_FEATURES
+
+/* This is the Tracks version of Track::monitoring_state().
+ *
+ * Ardour developers: try to flag or fix issues if parts of the libardour API
+ * change in ways that invalidate this
+ */
+
+MonitorState
+Route::monitoring_state () const
+{
+       /* Explicit requests */
+
+       if (_monitoring != MonitorInput) {
+               return MonitoringInput;
+       }
+
+       if (_monitoring & MonitorDisk) {
+               return MonitoringDisk;
+       }
+
+       /* This is an implementation of the truth table in doc/monitor_modes.pdf;
+          I don't think it's ever going to be too pretty too look at.
+       */
+
+       // GZ: NOT USED IN TRACKS
+       //bool const auto_input = _session.config.get_auto_input ();
+       //bool const software_monitor = Config->get_monitoring_model() == SoftwareMonitoring;
+       //bool const tape_machine_mode = Config->get_tape_machine_mode ();
+
+       bool const roll = _session.transport_rolling ();
+       bool const track_rec = _diskstream->record_enabled ();
+       bool session_rec = _session.actively_recording ();
+
+       if (track_rec) {
+
+               if (!session_rec && roll) {
+                       return MonitoringDisk;
+               } else {
+                       return MonitoringInput;
+               }
+
+       } else {
+
+               if (roll) {
+                       return MonitoringDisk;
+               }
+       }
+
+       return MonitoringSilence;
+}
+
+#else
+
+/* This is the Ardour/Mixbus version of Track::monitoring_state().
+ *
+ * Tracks developers: do NOT modify this method under any circumstances.
+ */
+
+MonitorState
+Route::monitoring_state () const
+{
+       if (!_disk_reader) {
+               return MonitoringInput;
+       }
+
+       /* Explicit requests */
+       MonitorChoice m (_monitoring_control->monitoring_choice());
+
+       if (m != MonitorAuto) {
+
+               MonitorState ms ((MonitorState) 0);
+
+               if (m & MonitorInput) {
+                       ms = MonitoringInput;
+               }
+
+               if (m & MonitorDisk) {
+                       ms = MonitorState (ms | MonitoringDisk);
+               }
+
+               return ms;
+       }
+
+       switch (_session.config.get_session_monitoring ()) {
+               case MonitorDisk:
+                       return MonitoringDisk;
+                       break;
+               case MonitorInput:
+                       return MonitoringInput;
+                       break;
+               default:
+                       break;
+       }
+
+       /* This is an implementation of the truth table in doc/monitor_modes.pdf;
+          I don't think it's ever going to be too pretty too look at.
+       */
+
+       bool const roll = _session.transport_rolling ();
+       bool const track_rec = _disk_writer->record_enabled ();
+       bool const auto_input = _session.config.get_auto_input ();
+       bool const software_monitor = Config->get_monitoring_model() == SoftwareMonitoring;
+       bool const tape_machine_mode = Config->get_tape_machine_mode ();
+       bool session_rec;
+
+       /* I suspect that just use actively_recording() is good enough all the
+        * time, but just to keep the semantics the same as they were before
+        * sept 26th 2012, we differentiate between the cases where punch is
+        * enabled and those where it is not.
+        *
+        * rg: I suspect this is not the case: monitoring may differ
+        */
+
+       if (_session.config.get_punch_in() || _session.config.get_punch_out() || _session.preroll_record_punch_enabled ()) {
+               session_rec = _session.actively_recording ();
+       } else {
+               session_rec = _session.get_record_enabled();
+       }
+
+       if (track_rec) {
+
+               if (!session_rec && roll && auto_input) {
+                       return MonitoringDisk;
+               } else {
+                       return software_monitor ? MonitoringInput : MonitoringSilence;
+               }
+
+       } else {
+
+               if (tape_machine_mode) {
+
+                       return MonitoringDisk;
+
+               } else {
+
+                       if (!roll && auto_input) {
+                               return software_monitor ? MonitoringInput : MonitoringSilence;
+                       } else {
+                               return MonitoringDisk;
+                       }
+
+               }
+       }
+
+       abort(); /* NOTREACHED */
+       return MonitoringSilence;
+}
+
+#endif