merge with master, fixing conflicts in 3 wscript files
[ardour.git] / libs / ardour / ltc_slave.cc
index 14cb3ae59d1cdb29e5d2d7fc4b6bf3f3e36c90e3..2888e7c11454e85da555cb69520eee160981d998 100644 (file)
 */
 #include <iostream>
 #include <errno.h>
-#include <poll.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "pbd/error.h"
+#include "pbd/pthread_utils.h"
 
 #include "ardour/debug.h"
 #include "ardour/slave.h"
@@ -39,19 +39,41 @@ using namespace MIDI;
 using namespace PBD;
 using namespace Timecode;
 
+#define FLYWHEEL_TIMEOUT ( 1 * session.frame_rate() )
+
 LTC_Slave::LTC_Slave (Session& s)
        : session (s)
 {
-       frames_per_ltc_frame = 1920.0; // samplerate / framerate
-       ltc_transport_pos = 0;
-       ltc_speed = 1.0;
-       last_timestamp = 0;
+       frames_per_ltc_frame = session.frames_per_timecode_frame();
+       timecode.rate = session.timecode_frames_per_second();
+       timecode.drop  = session.timecode_drop_frames();
+
+       did_reset_tc_format = false;
+       delayedlocked = 10;
+       monotonic_cnt = 0;
+       fps_detected=false;
+
+       ltc_timecode = session.config.get_timecode_format();
+       a3e_timecode = session.config.get_timecode_format();
+       printed_timecode_warning = false;
+       ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
+       memset(&prev_frame, 0, sizeof(LTCFrameExt));
 
        decoder = ltc_decoder_create((int) frames_per_ltc_frame, 128 /*queue size*/);
+
+       session.config.ParameterChanged.connect_same_thread (config_connection, boost::bind (&LTC_Slave::parameter_changed, this, _1));
+       parse_timecode_offset();
+       reset();
+       resync_latency();
+       session.Xrun.connect_same_thread (port_connections, boost::bind (&LTC_Slave::resync_xrun, this));
+       session.engine().GraphReordered.connect_same_thread (port_connections, boost::bind (&LTC_Slave::resync_latency, this));
 }
 
 LTC_Slave::~LTC_Slave()
 {
+       port_connections.drop_connections();
+       config_connection.disconnect();
+
        if (did_reset_tc_format) {
                session.config.set_timecode_format (saved_tc_format);
        }
@@ -59,29 +81,36 @@ LTC_Slave::~LTC_Slave()
        ltc_decoder_free(decoder);
 }
 
-bool
-LTC_Slave::give_slave_full_control_over_transport_speed() const
-{
-       return true; // DLL align to engine transport
-       // return false; // for Session-level computed varispeed
+void
+LTC_Slave::parse_timecode_offset() {
+       Timecode::Time offset_tc;
+       Timecode::parse_timecode_format(session.config.get_slave_timecode_offset(), offset_tc);
+       offset_tc.rate = session.timecode_frames_per_second();
+       offset_tc.drop = session.timecode_drop_frames();
+       session.timecode_to_sample(offset_tc, timecode_offset, false, false);
+       timecode_negative_offset = offset_tc.negative;
 }
 
-ARDOUR::framecnt_t
-LTC_Slave::resolution () const
+void
+LTC_Slave::parameter_changed (std::string const & p)
 {
-       return (framecnt_t) (frames_per_ltc_frame);
+       if (p == "slave-timecode-offset"
+                       || p == "timecode-format"
+                       ) {
+               parse_timecode_offset();
+       }
 }
 
 ARDOUR::framecnt_t
-LTC_Slave::seekahead_distance () const
+LTC_Slave::resolution () const
 {
-       return (framecnt_t) (frames_per_ltc_frame * 2);
+       return (framecnt_t) (session.frame_rate() / 1000);
 }
 
 bool
 LTC_Slave::locked () const
 {
-       return true;
+       return (delayedlocked < 5);
 }
 
 bool
@@ -90,37 +119,206 @@ LTC_Slave::ok() const
        return true;
 }
 
-int
-LTC_Slave::parse_ltc(const jack_nframes_t nframes, const jack_default_audio_sample_t * const in, const framecnt_t posinfo)
+void
+LTC_Slave::resync_xrun()
+{
+       DEBUG_TRACE (DEBUG::LTC, "LTC resync_xrun()\n");
+       engine_dll_initstate = 0;
+}
+
+void
+LTC_Slave::resync_latency()
+{
+       DEBUG_TRACE (DEBUG::LTC, "LTC resync_latency()\n");
+       engine_dll_initstate = 0;
+
+       if (!session.deletion_in_progress() && session.ltc_output_io()) { /* check if Port exits */
+               boost::shared_ptr<Port> ltcport = session.ltc_input_port();
+               ltcport->get_connected_latency_range (ltc_slave_latency, false);
+       }
+}
+
+void
+LTC_Slave::reset()
+{
+       DEBUG_TRACE (DEBUG::LTC, "LTC reset()\n");
+       last_timestamp = 0;
+       current_delta = 0;
+       transport_direction = 0;
+       ltc_speed = 0;
+       engine_dll_initstate = 0;
+}
+
+void
+LTC_Slave::parse_ltc(const ARDOUR::pframes_t nframes, const Sample* const in, const ARDOUR::framecnt_t posinfo)
 {
-       jack_nframes_t i;
+       pframes_t i;
        unsigned char sound[8192];
-       if (nframes > 8192) return 1;
+       if (nframes > 8192) {
+               /* TODO warn once or wrap, loop conversion below
+                * does jack/A3 support > 8192 spp anyway?
+                */
+               return;
+       }
 
        for (i = 0; i < nframes; i++) {
                const int snd=(int)rint((127.0*in[i])+128.0);
                sound[i] = (unsigned char) (snd&0xff);
        }
        ltc_decoder_write(decoder, sound, nframes, posinfo);
-       return 0;
+       return;
 }
 
 bool
-LTC_Slave::process_ltc(framepos_t now, framecnt_t nframes)
+LTC_Slave::equal_ltc_frame_time(LTCFrame *a, LTCFrame *b) {
+       if (       a->frame_units != b->frame_units
+               || a->frame_tens  != b->frame_tens
+               || a->dfbit       != b->dfbit
+               || a->secs_units  != b->secs_units
+               || a->secs_tens   != b->secs_tens
+               || a->mins_units  != b->mins_units
+               || a->mins_tens   != b->mins_tens
+               || a->hours_units != b->hours_units
+               || a->hours_tens  != b->hours_tens
+            ) {
+               return false;
+       }
+       return true;
+}
+
+bool
+LTC_Slave::detect_discontinuity(LTCFrameExt *frame, int fps, bool fuzzy) {
+       bool discontinuity_detected = false;
+
+       if (fuzzy && (
+                 ( frame->reverse && prev_frame.ltc.frame_units == 0)
+               ||(!frame->reverse && frame->ltc.frame_units == 0)
+               )) {
+               memcpy(&prev_frame, frame, sizeof(LTCFrameExt));
+               return false;
+       }
+
+       if (frame->reverse) {
+               ltc_frame_decrement(&prev_frame.ltc, fps, LTC_TV_525_60, 0);
+       } else {
+               ltc_frame_increment(&prev_frame.ltc, fps, LTC_TV_525_60, 0);
+       }
+       if (!equal_ltc_frame_time(&prev_frame.ltc, &frame->ltc)) {
+               discontinuity_detected = true;
+       }
+
+    memcpy(&prev_frame, frame, sizeof(LTCFrameExt));
+    return discontinuity_detected;
+}
+
+bool
+LTC_Slave::detect_ltc_fps(int frameno, bool df)
 {
-       Time timecode;
-       bool have_frame = false;
+       bool fps_changed = false;
+       double detected_fps = 0;
+       if (frameno > ltc_detect_fps_max)
+       {
+               ltc_detect_fps_max = frameno;
+       }
+       ltc_detect_fps_cnt++;
+
+       if (ltc_detect_fps_cnt > 40) {
+               if (ltc_detect_fps_cnt > ltc_detect_fps_max) {
+                       detected_fps = ltc_detect_fps_max + 1;
+                       if (df) {
+                               /* LTC df -> indicates fractional framerate */
+                               if (Config->get_timecode_source_2997()) {
+                                       detected_fps = detected_fps * 999.0 / 1000.0;
+                               } else {
+                                       detected_fps = detected_fps * 1000.0 / 1001.0;
+                               }
+                       }
+
+                       if (timecode.rate != detected_fps || timecode.drop != df) {
+                               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC detected FPS: %1%2\n", detected_fps, df?"df":"ndf"));
+                       } else {
+                               detected_fps = 0; /* no cange */
+                       }
+               }
+               ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
+       }
 
-       framepos_t sess_pos = session.transport_frame(); // corresponds to now
-       //sess_pos -= session.engine().frames_since_cycle_start();
+       /* when changed */
+       if (detected_fps != 0 && (detected_fps != timecode.rate || df != timecode.drop)) {
+               timecode.rate = detected_fps;
+               timecode.drop = df;
+               frames_per_ltc_frame = double(session.frame_rate()) / timecode.rate;
+               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC reset to FPS: %1%2 ; audio-frames per LTC: %3\n",
+                               detected_fps, df?"df":"ndf", frames_per_ltc_frame));
+               fps_changed=true;
+       }
 
-       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC Process eng-tme: %1 eng-pos: %2\n", now, sess_pos));
+       /* poll and check session TC */
+       TimecodeFormat tc_format = apparent_timecode_format();
+       TimecodeFormat cur_timecode = session.config.get_timecode_format();
+
+       if (Config->get_timecode_sync_frame_rate()) {
+               /* enforce time-code */
+               if (!did_reset_tc_format) {
+                       saved_tc_format = cur_timecode;
+                       did_reset_tc_format = true;
+               }
+               if (cur_timecode != tc_format) {
+                       if (ceil(Timecode::timecode_to_frames_per_second(cur_timecode)) != ceil(Timecode::timecode_to_frames_per_second(tc_format))) {
+                               warning << string_compose(_("Session framerate adjusted from %1 to LTC's %2."),
+                                               Timecode::timecode_format_name(cur_timecode),
+                                               Timecode::timecode_format_name(tc_format))
+                                       << endmsg;
+                       }
+                       session.config.set_timecode_format (tc_format);
+               }
+       } else {
+               /* only warn about TC mismatch */
+               if (ltc_timecode != tc_format) printed_timecode_warning = false;
+               if (a3e_timecode != cur_timecode) printed_timecode_warning = false;
+
+               if (cur_timecode != tc_format && ! printed_timecode_warning) {
+                       if (ceil(Timecode::timecode_to_frames_per_second(cur_timecode)) != ceil(Timecode::timecode_to_frames_per_second(tc_format))) {
+                               warning << string_compose(_("Session and LTC framerate mismatch: LTC:%1 Session:%2."),
+                                               Timecode::timecode_format_name(tc_format),
+                                               Timecode::timecode_format_name(cur_timecode))
+                                       << endmsg;
+                       }
+                       printed_timecode_warning = true;
+               }
+       }
+       ltc_timecode = tc_format;
+       a3e_timecode = cur_timecode;
+
+       return fps_changed;
+}
 
+void
+LTC_Slave::process_ltc(framepos_t const /*now*/)
+{
        LTCFrameExt frame;
-       while (ltc_decoder_read(decoder,&frame)) {
+       enum LTC_TV_STANDARD tv_standard = LTC_TV_625_50;
+       while (ltc_decoder_read(decoder, &frame)) {
                SMPTETimecode stime;
+
                ltc_frame_to_time(&stime, &frame.ltc, 0);
-#if 1
+               timecode.negative  = false;
+               timecode.subframes  = 0;
+
+               /* set timecode.rate and timecode.drop: */
+               bool ltc_is_static = equal_ltc_frame_time(&prev_frame.ltc, &frame.ltc);
+
+               if (detect_discontinuity(&frame, ceil(timecode.rate), !fps_detected)) {
+                       if (fps_detected) { ltc_detect_fps_cnt = ltc_detect_fps_max = 0; }
+                       fps_detected=false;
+               }
+
+               if (!ltc_is_static && detect_ltc_fps(stime.frame, (frame.ltc.dfbit)? true : false)) {
+                       reset();
+                       fps_detected=true;
+               }
+
+#if 0 // Devel/Debug
                fprintf(stdout, "LTC %02d:%02d:%02d%c%02d | %8lld %8lld%s\n",
                        stime.hours,
                        stime.mins,
@@ -133,25 +331,41 @@ LTC_Slave::process_ltc(framepos_t now, framecnt_t nframes)
                        );
 #endif
 
-               timecode.negative  = false;
-               timecode.subframes  = 0;
-               timecode.drop  = (frame.ltc.dfbit)? true : false;
-               timecode.rate  = 25.0; // XXX
-
                /* when a full LTC frame is decoded, the timecode the LTC frame
                 * is referring has just passed.
                 * So we send the _next_ timecode which
                 * is expected to start at the end of the current frame
                 */
                int fps_i = ceil(timecode.rate);
+
+               switch(fps_i) {
+                       case 30:
+                               if (timecode.drop) {
+                                       tv_standard = LTC_TV_525_60;
+                               } else {
+                                       tv_standard = LTC_TV_1125_60;
+                               }
+                               break;
+                       case 25:
+                               tv_standard = LTC_TV_625_50;
+                               break;
+                       default:
+                               tv_standard = LTC_TV_FILM_24; /* == LTC_TV_1125_60 == no offset, 24,30fps BGF */
+                               break;
+               }
+
                if (!frame.reverse) {
-                       ltc_frame_increment(&frame.ltc, fps_i , 0);
+                       ltc_frame_increment(&frame.ltc, fps_i, tv_standard, 0);
                        ltc_frame_to_time(&stime, &frame.ltc, 0);
+                       transport_direction = 1;
+                       frame.off_start -= ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
+                       frame.off_end -= ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
                } else {
-                       ltc_frame_decrement(&frame.ltc, fps_i , 0);
+                       ltc_frame_decrement(&frame.ltc, fps_i, tv_standard, 0);
                        int off = frame.off_end - frame.off_start;
-                       frame.off_start += off;
-                       frame.off_end += off;
+                       frame.off_start += off - ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
+                       frame.off_end += off - ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
+                       transport_direction = -1;
                }
 
                timecode.hours   = stime.hours;
@@ -159,90 +373,181 @@ LTC_Slave::process_ltc(framepos_t now, framecnt_t nframes)
                timecode.seconds = stime.secs;
                timecode.frames  = stime.frame;
 
-               framepos_t ltc_frame;
-               session.timecode_to_sample (timecode, ltc_frame, true, false);
-
-               double poff = (frame.off_end - now);
-
-               ltc_transport_pos = ltc_frame - poff;
-               frames_per_ltc_frame = (double(session.frame_rate()) / timecode.rate);
-               //frames_per_ltc_frame = frame.off_end - frame.off_start; // the first one is off.
-
-               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC frame: %1 poff: %2 pos :%3\n", ltc_frame, poff, ltc_transport_pos));
+               /* map LTC timecode to session TC setting */
+               framepos_t ltc_frame; ///< audio-frame corresponding to LTC frame
+               Timecode::timecode_to_sample (timecode, ltc_frame, true, false,
+                       double(session.frame_rate()),
+                       session.config.get_subframes_per_frame(),
+                       timecode_negative_offset, timecode_offset
+                       );
 
-               if (last_timestamp == 0 || ((now - last_timestamp) > 4 * frames_per_ltc_frame) ) {
-                       init_ltc_dll(ltc_frame, frames_per_ltc_frame);
-                       ltc_speed = 1.0; // XXX
+               framepos_t cur_timestamp = frame.off_end + 1;
+               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC F: %1 LF: %2  N: %3 L: %4\n", ltc_frame, last_ltc_frame, cur_timestamp, last_timestamp));
+               if (frame.off_end + 1 <= last_timestamp || last_timestamp == 0) {
+                       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: UNCHANGED: %1\n", ltc_speed));
                } else {
+                       ltc_speed = double(ltc_frame - last_ltc_frame) / double(cur_timestamp - last_timestamp);
+                       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: %1\n", ltc_speed));
+               }
 
-                       double e = (double(ltc_frame) - poff - double(sess_pos));
-                       // update DLL
-                       t0 = t1;
-                       t1 += b * e + e2;
-                       e2 += c * e;
-
-                       ltc_speed = (t1 - t0) / frames_per_ltc_frame;
-                       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC DLL t0:%1 t1:%2 err:%3 spd:%4 ddt:%5\n", t0, t1, e, ltc_speed, e2 - frames_per_ltc_frame));
-
+               if (fabs(ltc_speed) > 10.0) {
+                       ltc_speed = 0;
                }
-               last_timestamp = now;
+
+               last_timestamp = frame.off_end + 1;
                last_ltc_frame = ltc_frame;
-               have_frame = true;
-       }
-       return have_frame;
+       } /* end foreach decoded LTC frame */
 }
 
 void
-LTC_Slave::init_ltc_dll(framepos_t tme, double dt)
+LTC_Slave::init_engine_dll (framepos_t pos, int32_t inc)
 {
-       omega = 2.0 * M_PI * dt / double(session.frame_rate());
+       double omega = 2.0 * M_PI * double(inc) / double(session.frame_rate());
        b = 1.4142135623730950488 * omega;
        c = omega * omega;
 
-       e2 = dt;
-       t0 = double(tme);
+       e2 = double(ltc_speed * inc);
+       t0 = double(pos);
        t1 = t0 + e2;
-       DEBUG_TRACE (DEBUG::LTC, string_compose ("[re-]init LTC DLL %1 %2 %3\n", t0, t1, e2));
+       DEBUG_TRACE (DEBUG::LTC, string_compose ("[re-]init Engine DLL %1 %2 %3\n", t0, t1, e2));
 }
 
 /* main entry point from session_process.cc
- * called from jack_process callback context
+ * called from process callback context
+ * so it is OK to use get_buffer()
  */
 bool
 LTC_Slave::speed_and_position (double& speed, framepos_t& pos)
 {
+       bool engine_init_called = false;
+       framepos_t now = session.engine().sample_time_at_cycle_start();
+       framepos_t sess_pos = session.transport_frame(); // corresponds to now
+       framecnt_t nframes = session.engine().samples_per_cycle();
+
+       Sample* in;
 
-       framepos_t now = session.engine().frame_time_at_cycle_start();
-       framecnt_t nframes = session.engine().frames_per_cycle();
-       jack_default_audio_sample_t *in;
-       jack_latency_range_t ltc_latency;
+       boost::shared_ptr<Port> ltcport = session.ltc_input_port();
 
-       Port *ltcport = session.engine().ltc_input_port();
-       ltcport->get_connected_latency_range(ltc_latency, false);
-       in = (jack_default_audio_sample_t*) jack_port_get_buffer (ltcport->jack_port(), nframes);
+       in = (Sample*) AudioEngine::instance()->port_engine().get_buffer (ltcport->port_handle(), nframes);
 
-       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC_Slave::speed_and_position - TID:%1 | latency: %2\n", ::pthread_self(), ltc_latency.max));
+       frameoffset_t skip = now - (monotonic_cnt + nframes);
+       monotonic_cnt = now;
+       DEBUG_TRACE (DEBUG::LTC, string_compose ("speed_and_position - TID:%1 | latency: %2 | skip %3\n", pthread_name(), ltc_slave_latency.max, skip));
+
+       if (last_timestamp == 0) {
+               engine_dll_initstate = 0;
+               delayedlocked++;
+       }
+       else if (engine_dll_initstate != transport_direction && ltc_speed != 0) {
+               engine_dll_initstate = transport_direction;
+               init_engine_dll(last_ltc_frame + rint(ltc_speed * double(2 * nframes + now - last_timestamp)),
+                               session.engine().samples_per_cycle());
+               engine_init_called = true;
+       }
 
        if (in) {
-               parse_ltc(nframes, in, now  + ltc_latency.max );
-               if (!process_ltc(now, nframes)) {
-                       /* fly wheel */
-                       double elapsed = (now - last_timestamp) * ltc_speed;
-                       ltc_transport_pos = last_ltc_frame + elapsed;
-                       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC fly wheel elapsed: %1 @speed %2\n", elapsed, ltc_speed));
+               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC Process eng-tme: %1 eng-pos: %2\n", now, sess_pos));
+               /* when the jack-graph changes and if ardour performs
+                * locates, the audioengine is stopped (skipping frames) while
+                * jack [time] moves along.
+                */
+               if (skip > 0) {
+                       DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames. Feeding silence to LTC parser.\n", skip));
+                       if (skip >= 8192) skip = 8192;
+                       unsigned char sound[8192];
+                       memset(sound, 0, sizeof(char) * skip);
+                       ltc_decoder_write(decoder, sound, nframes, now);
+               } else if (skip != 0) {
+                       /* this should never happen. it may if monotonic_cnt, now overflow on 64bit */
+                       DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames\n", skip));
+                       reset();
                }
+
+               parse_ltc(nframes, in, now - ltc_slave_latency.max );
+               process_ltc(now);
+       }
+
+       if (last_timestamp == 0) {
+               DEBUG_TRACE (DEBUG::LTC, "last timestamp == 0\n");
+               speed = 0;
+               pos = session.transport_frame();
+               return true;
+       } else if (ltc_speed != 0) {
+               delayedlocked = 0;
+       }
+
+       if (abs(now - last_timestamp) > FLYWHEEL_TIMEOUT) {
+               DEBUG_TRACE (DEBUG::LTC, "flywheel timeout\n");
+               reset();
+               speed = 0;
+               pos = session.transport_frame();
+               return true;
+       }
+
+       /* it take 2 cycles from naught to rolling.
+        * during these to initial cycles the speed == 0
+        *
+        * the first cycle:
+        * DEBUG::Slave: slave stopped, move to NNN
+        * DEBUG::Transport: Request forced locate to NNN
+        * DEBUG::Slave: slave state 0 @ NNN speed 0 cur delta VERY-LARGE-DELTA avg delta 1800
+        * DEBUG::Slave: silent motion
+        * DEBUG::Transport: realtime stop @ NNN
+        * DEBUG::Transport: Butler transport work, todo = PostTransportStop,PostTransportLocate,PostTransportClearSubstate
+        *
+        * [engine skips frames to locate, jack time keeps rolling on]
+        *
+        * the second cycle:
+        *
+        * DEBUG::LTC: [re-]init Engine DLL
+        * DEBUG::Slave: slave stopped, move to NNN+
+        * ...
+        *
+        * we need to seek two cycles ahead: 2 * nframes
+        */
+       if (engine_dll_initstate == 0) {
+               DEBUG_TRACE (DEBUG::LTC, "engine DLL not initialized. ltc_speed\n");
+               speed = 0;
+               pos = last_ltc_frame + rint(ltc_speed * double(2 * nframes + now - last_timestamp));
+               return true;
+       }
+
+       /* interpolate position according to speed and time since last LTC-frame*/
+       double speed_flt = ltc_speed;
+       double elapsed = (now - last_timestamp) * speed_flt;
+
+       if (!engine_init_called) {
+               const double e = elapsed + double (last_ltc_frame - sess_pos);
+               t0 = t1;
+               t1 += b * e + e2;
+               e2 += c * e;
+               speed_flt = (t1 - t0) / double(session.engine().samples_per_cycle());
+               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC engine DLL t0:%1 t1:%2 err:%3 spd:%4 ddt:%5\n", t0, t1, e, speed_flt, e2 - session.engine().samples_per_cycle() ));
+       } else {
+               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC adjusting elapsed (no DLL) from %1 by %2\n", elapsed, (2 * nframes * ltc_speed)));
+               speed_flt = 0;
+               elapsed += 2.0 * nframes * ltc_speed; /* see note above */
        }
 
-       if (((now - last_timestamp) > 4 * frames_per_ltc_frame) ) {
-               DEBUG_TRACE (DEBUG::LTC, "LTC no-signal - reset\n");
-               speed = ltc_speed = 0;
+       pos = last_ltc_frame + rint(elapsed);
+       speed = speed_flt;
+       current_delta = (pos - sess_pos);
+
+       if (((pos < 0) || (labs(current_delta) > 2 * session.frame_rate()))) {
+               DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC large drift: %1\n", current_delta));
+               reset();
+               speed = 0;
                pos = session.transport_frame();
-               last_timestamp = 0;
                return true;
        }
 
-       pos = ltc_transport_pos;
-       speed = ltc_speed;
+       DEBUG_TRACE (DEBUG::LTC, string_compose ("LTCsync spd: %1 pos: %2 | last-pos: %3 elapsed: %4 delta: %5\n",
+                                                speed, pos, last_ltc_frame, elapsed, current_delta));
+
+       /* provide a .1% deadzone to lock the speed */
+       if (fabs(speed - 1.0) <= 0.001) {
+               speed = 1.0;
+       }
 
        return true;
 }
@@ -250,6 +555,43 @@ LTC_Slave::speed_and_position (double& speed, framepos_t& pos)
 Timecode::TimecodeFormat
 LTC_Slave::apparent_timecode_format () const
 {
-       /* XXX to be computed, determined from incoming stream */
-       return timecode_25;
+       if      (timecode.rate == 24 && !timecode.drop)
+               return timecode_24;
+       else if (timecode.rate == 25 && !timecode.drop)
+               return timecode_25;
+       else if (rint(timecode.rate * 100) == 2997 && !timecode.drop)
+               return (Config->get_timecode_source_2997() ? timecode_2997000 : timecode_2997);
+       else if (rint(timecode.rate * 100) == 2997 &&  timecode.drop)
+               return (Config->get_timecode_source_2997() ? timecode_2997000drop : timecode_2997drop);
+       else if (timecode.rate == 30 &&  timecode.drop)
+               return timecode_2997drop; // timecode_30drop; // LTC counting to 30 frames w/DF *means* 29.97 df
+       else if (timecode.rate == 30 && !timecode.drop)
+               return timecode_30;
+
+       /* XXX - unknown timecode format */
+       return session.config.get_timecode_format();
+}
+
+std::string
+LTC_Slave::approximate_current_position() const
+{
+       if (last_timestamp == 0) {
+               return " --:--:--:--";
+       }
+       return Timecode::timecode_format_time(timecode);
+}
+
+std::string
+LTC_Slave::approximate_current_delta() const
+{
+       char delta[80];
+       if (last_timestamp == 0 || engine_dll_initstate == 0) {
+               snprintf(delta, sizeof(delta), "\u2012\u2012\u2012\u2012");
+       } else if ((monotonic_cnt - last_timestamp) > 2 * frames_per_ltc_frame) {
+               snprintf(delta, sizeof(delta), _("flywheel"));
+       } else {
+               snprintf(delta, sizeof(delta), "\u0394<span foreground=\"green\" face=\"monospace\" >%s%s%" PRIi64 "</span>sm",
+                               LEADINGZERO(llabs(current_delta)), PLUSMINUS(-current_delta), llabs(current_delta));
+       }
+       return std::string(delta);
 }