Timeline: Add option for per-track delay-free playback latency compensation. Disabled by default.

timeline/src/Engine/Playback_DS.C

@@ -66,9 +66,9 @@ Playback_DS::seek ( nframes_t frame )
 /** set the playback delay to /frames/ frames. This be called prior to
 a seek. */
 void
-Playback_DS::delay ( nframes_t frames )
+Playback_DS::undelay ( nframes_t delay )
 {
-    _delay = frames;
+    _undelay = delay;
 }
 
 /** read /nframes/ from the attached track into /buf/ */
@@ -94,13 +94,8 @@ Playback_DS::read_block ( sample_t *buf, nframes_t nframes )
     
     if ( sequence() )
     {
-        /* FIXME: how does this work if _delay is not a multiple of bufsize? */
-        
-        if ( _frame >= _delay )
-        {
-            if ( ! sequence()->play( buf, _frame - _delay, nframes, channels() ) )
+        if ( ! sequence()->play( buf, _frame + _undelay, nframes, channels() ) )
             WARNING( "Programming error?" );
-        }
         
         _frame += nframes;
     }

timeline/src/Engine/Playback_DS.H

@@ -27,14 +27,15 @@ class Playback_DS : public Disk_Stream
 
     void flush ( void ) { base_flush( true ); }
 
-    volatile nframes_t _delay; /* number of frames this diskstream should be delayed by */
+    volatile nframes_t _undelay; /* number of frames this diskstream
+                                  * should be undelayed by */
 
 public:
 
     Playback_DS ( Track *th, float frame_rate, nframes_t nframes, int channels ) :
         Disk_Stream( th, frame_rate, nframes, channels )
         {
-            _delay = 0;
+            _undelay = 0;
 
             run();
         }
@@ -45,6 +46,6 @@ public:
     void seek ( nframes_t frame );
     nframes_t process ( nframes_t nframes );
 
-    void delay ( nframes_t v );
+    void undelay ( nframes_t v );
 
 };

timeline/src/Engine/Track.C

@@ -234,17 +234,19 @@ Track::seek ( nframes_t frame )
 {
     THREAD_ASSERT( RT );
 
+    compute_latency_compensation();
+
     if ( playback_ds )
         return playback_ds->seek( frame );
 }
 
 void
-Track::delay ( nframes_t frames )
+Track::undelay ( nframes_t nframes )
 {
 //    THREAD_ASSERT( RT );
 
     if ( playback_ds )
-        playback_ds->delay( frames );
+        playback_ds->undelay( nframes );
 }
 
 /* THREAD: RT (non-RT) */
@@ -360,3 +362,21 @@ Track::finalize ( Capture *c, nframes_t frame )
 
     timeline->unlock();
 }
+
+void
+Track::compute_latency_compensation ( void )
+{
+    if ( Timeline::playback_latency_compensation && output.size() )
+    {
+        nframes_t min,max;
+        output[0].get_latency( JACK::Port::Output, &min, &max );
+
+        DMESSAGE( "Track %s, setting undelay to %lu", name(), (unsigned long)min);
+
+        undelay( min );
+    }
+    else
+    {
+        undelay( 0 );
+    }
+}

timeline/src/TLE.fl

@@ -325,6 +325,11 @@ pi.run();}
                 label {Capture Format} open
                 xywh {25 25 74 25}
               } {}
+              MenuItem {} {
+                label {Playback Latency Compensation}
+                callback {Timeline::playback_latency_compensation = menu_picked_value( o );} selected
+                xywh {55 55 40 25} type Toggle
+              }
             }
             MenuItem {} {
               label {&New}
@@ -364,9 +369,7 @@ main_window->redraw();}
             }
             MenuItem {} {
               label {&Open}
-              callback {
-
-char *path = read_line( user_config_dir, "default_path" );
+              callback {char *path = read_line( user_config_dir, "default_path" );
 
 const char *name = fl_dir_chooser( "Open Project", path );
 
@@ -1107,7 +1110,7 @@ if ( logo_box->image() )
         code1 {o->label( NULL );}
       }
       Fl_Text_Editor notes_field {
-        label {Notes:} selected
+        label {Notes:}
         private xywh {20 420 480 245} color 47 selection_color 31 textsize 18 textcolor 92
         code0 {o->buffer( new Fl_Text_Buffer() );}
         code1 {o->buffer()->loadfile( "notes" );}

timeline/src/Timeline.C

@@ -73,6 +73,7 @@ bool Timeline::snapping_on_hold = false;
 bool Timeline::snap_magnetic = true;
 bool Timeline::follow_playhead = true;
 bool Timeline::center_playhead = true;
+bool Timeline::playback_latency_compensation = false;
 
 const float UPDATE_FREQ = 1.0f / 18.0f;
 

timeline/src/Timeline.H

@@ -155,6 +155,7 @@ public:
     static bool snap_magnetic;
     static bool follow_playhead;
     static bool center_playhead;
+    static bool playback_latency_compensation;
 
     Tempo_Sequence *tempo_track;
     Time_Sequence  *time_track;

timeline/src/Track.H

@@ -253,8 +253,8 @@ public:
     nframes_t process_input ( nframes_t nframes );
     nframes_t process_output ( nframes_t nframes );
     void seek ( nframes_t frame );
-    void delay ( nframes_t frames );
-
+    void undelay ( nframes_t frames );
+    void compute_latency_compensation ( void );
     void record ( Capture *c, nframes_t frame );
     void write ( Capture *c, sample_t *buf, nframes_t nframes );
     void finalize ( Capture *c, nframes_t frame );