Implement capture-offset latency compensation.

Timeline/Engine/Engine.C

@@ -205,7 +205,6 @@ Engine::timebase ( jack_transport_state_t, jack_nframes_t, jack_position_t *pos,
 
     /* FIXME: fill this in */
     pos->bar_start_tick = 0;
-
 }
 
 /* THREAD: RT */

Timeline/Engine/Engine.H

@@ -86,7 +86,14 @@ public:
     void freewheeling ( bool yes );
     bool zombified ( void ) const { return _zombified; }
 
+    nframes_t system_latency ( void ) const { return nframes(); }
+
     float cpu_load ( void ) const { return jack_cpu_load( _client ); }
+
+    float frames_to_milliseconds ( nframes_t frames )
+        {
+            return ( frames * 1000 ) / (float)frame_rate();
+        }
 };
 
 

Timeline/Engine/Playback_DS.C

@@ -60,6 +60,14 @@ Playback_DS::seek ( nframes_t frame )
     flush();
 }
 
+/** set the playback delay to /frames/ frames. This be called prior to
+a seek. */
+void
+Playback_DS::delay ( nframes_t frames )
+{
+    _delay = frames;
+}
+
 /** read /nframes/ from the attached track into /buf/ */
 void
 Playback_DS::read_block ( sample_t *buf, nframes_t nframes )
@@ -76,16 +84,22 @@ Playback_DS::read_block ( sample_t *buf, nframes_t nframes )
 
     if ( ! sequence() )
     {
+        /* FIXME: what to do here? */
 //        _frame += _nframes;
         return;
     }
 
     timeline->rdlock();
 
-    if ( sequence()->play( buf, _frame, nframes, channels() ) )
-        _frame += nframes;
-    else
+    /* FIXME: how does this work if _delay is not a multiple of bufsize? */
+
+    if ( _frame >= _delay )
+    {
+        if ( ! sequence()->play( buf, _frame - _delay, nframes, channels() ) )
             WARNING( "Programming error?" );
+    }
+
+    _frame += nframes;
 
     timeline->unlock();
 }

Timeline/Engine/Playback_DS.H

@@ -27,11 +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 */
+
 public:
 
     Playback_DS ( Track *th, float frame_rate, nframes_t nframes, int channels ) :
         Disk_Stream( th, frame_rate, nframes, channels )
         {
+            _delay = 0;
+
             run();
         }
 
@@ -39,4 +43,6 @@ public:
     void seek ( nframes_t frame );
     nframes_t process ( nframes_t nframes );
 
+    void delay ( nframes_t v );
+
 };

Timeline/Engine/Port.C

@@ -95,6 +95,33 @@ Port::activate ( const char *name, type_e dir )
                                 0 );
 }
 
+/** returns the sum of latency of all ports between this one and a
+    terminal port. */
+/* FIMXE: how does JACK know that input A of client Foo connects to
+output Z of the same client in order to draw the line through Z to a
+terminal port? And, if this determination cannot be made, what use is
+this function? */
+
+nframes_t
+Port::total_latency ( void ) const
+{
+    return jack_port_get_total_latency( engine->client(), _port );
+}
+
+/** returns the number of frames of latency assigned to this port */
+nframes_t
+Port::latency ( void ) const
+{
+    return jack_port_get_latency( _port );
+}
+
+/** inform JACK that port has /frames/ frames of latency */
+void
+Port::latency ( nframes_t frames )
+{
+    jack_port_set_latency( _port, frames );
+}
+
 void
 Port::shutdown ( void )
 {

Timeline/Engine/Port.H

@@ -63,7 +63,9 @@ public:
     const char * name ( void ) const { return _name; }
     bool name ( const char *name );
     bool name ( const char *base, int n, const char *type=0 );
-
+    nframes_t total_latency ( void ) const;
+    nframes_t latency ( void ) const;
+    void latency ( nframes_t frames );
 
     void activate ( const char *name, type_e dir );
     void shutdown ( void );

Timeline/Engine/Timeline.C

@@ -235,3 +235,15 @@ Timeline::total_capture_xruns ( void )
 
     return r;
 }
+
+#include "Engine.H"
+extern Engine *engine;
+
+nframes_t
+Timeline::total_output_latency ( void ) const
+{
+    /* Due to flaws in the JACK latency reporting API, we cannot
+     * reliably account for software latency. Using the system latency
+     * is the best we can do here. */
+    return engine->system_latency();
+}

Timeline/Engine/Track.C

@@ -204,6 +204,15 @@ Track::seek ( nframes_t frame )
         return playback_ds->seek( frame );
 }
 
+void
+Track::delay ( nframes_t frames )
+{
+//    THREAD_ASSERT( RT );
+
+    if ( playback_ds )
+        playback_ds->delay( frames );
+}
+
 /* THREAD: RT (non-RT) */
 void
 Track::resize_buffers ( nframes_t nframes )
@@ -266,9 +275,29 @@ Track::finalize ( Capture *c, nframes_t frame )
 {
     THREAD_ASSERT( Capture );
 
+    /* adjust region start for latency */
+    /* FIXME: is just looking at the first channel good enough? */
+
     c->region->finalize( frame );
     DMESSAGE( "finalizing audio file" );
     c->audio_file->finalize();
 
+    nframes_t capture_offset = 0;
+
+    /* Add the system latency twice. Once for the input (usually
+     * required) and again for the output latency of whatever we're
+     * playing along to (should only apply when overdubbing) */
+
+    /* Limitations in the JACK latency reporting API prevent us from
+     * compensating from any software latency introduced by other
+     * clients in our graph... Oh well */
+
+    capture_offset += engine->system_latency();
+    capture_offset += engine->system_latency();
+
+    DMESSAGE( "Adjusting capture by %lu frames.", (unsigned long)capture_offset );
+
+    c->region->offset( capture_offset );
+
     delete c->audio_file;
 }

Timeline/TLE.fl

@@ -205,7 +205,7 @@ Loggable::progress_callback( &TLE::progress_cb, this );} {}
       label Timeline
       callback {if ( Fl::event_key() != FL_Escape )
 	o->hide();} open
-      private xywh {133 113 1025 770} type Double resizable xclass Non_DAW visible
+      private xywh {102 111 1025 770} type Double resizable xclass Non_DAW visible
     } {
       Fl_Menu_Bar menubar {open
         private xywh {0 0 1024 25}
@@ -577,7 +577,7 @@ ab.run();}
         }
       }
       Fl_Group {} {open
-        xywh {0 23 1025 51}
+        xywh {0 1 1025 73}
       } {
         Fl_Pack {} {open
           xywh {0 23 483 46} type HORIZONTAL
@@ -669,6 +669,10 @@ ab.run();}
           code0 {\#include "FL/Fl_Blinker.H"}
           class Fl_Blinker
         }
+        Fl_Box stats_box {
+          label {<stats>} selected
+          xywh {810 1 215 21} labelsize 13 labelcolor 53 align 88
+        }
       }
       Fl_Progress progress {
         label {0%}
@@ -682,13 +686,9 @@ ab.run();}
       }
       Fl_Box project_name {
         label {<project name>}
-        private xywh {450 0 475 22} labeltype SHADOW_LABEL labelfont 2
+        private xywh {450 0 365 22} labeltype SHADOW_LABEL labelfont 2
         code0 {o->label( Project::name() );}
       }
-      Fl_Value_Output xruns_output {
-        label {xruns:}
-        private xywh {980 2 44 20} maximum 40000 step 1
-      }
     }
   }
   Function {menu_picked_value( const Fl_Menu_ *m )} {private return_type {static int}
@@ -757,9 +757,13 @@ if ( timeline->total_capture_xruns() )
 if ( timeline->total_playback_xruns() )
 	playback_buffer_progress->selection_color( FL_RED );
 
+static char stats[100];
 
+snprintf( stats, sizeof( stats ), "latency: %.1fms, xruns: %d",
+	engine->frames_to_milliseconds( timeline->total_output_latency() ),
+	engine->xruns() );
 
-xruns_output->value( engine->xruns() );
+stats_box->label( stats );
 
 static bool zombie = false;
 

Timeline/Timeline.H

@@ -205,6 +205,7 @@ public:
 
     int total_playback_xruns ( void );
     int total_capture_xruns ( void );
+    nframes_t total_output_latency ( void ) const;
 
     bool record ( void );
     void stop ( void );

Timeline/Track.H

@@ -215,6 +215,7 @@ 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 record ( Capture *c, nframes_t frame );
     void write ( Capture *c, sample_t *buf, nframes_t nframes );