configurable export preroll

[ardour.git] / libs / ardour / session_export.cc

diff --git a/libs/ardour/session_export.cc b/libs/ardour/session_export.cc
index 890871696517c7986622ef77212208df0ab08272..efb731463f7151e2adcc50688e08f5669416655c 100644 (file)
--- a/libs/ardour/session_export.cc
+++ b/libs/ardour/session_export.cc
@@ -73,12 +73,16 @@ Session::pre_export ()
                }
        }
 
-       /* make sure we are actually rolling */
+       /* prepare transport */
+
+       realtime_stop (true, true);
 
        if (get_record_enabled()) {
                disable_record (false);
        }
 
+       unset_play_loop ();
+
        /* no slaving */
 
        post_export_sync = config.get_external_sync ();
@@ -105,7 +109,8 @@ Session::start_audio_export (framepos_t position)
        if (!_exporting) {
                pre_export ();
        }
-       _export_started = false;
+
+       _export_preroll = Config->get_export_preroll() * nominal_frame_rate ();
 
        /* We're about to call Track::seek, so the butler must have finished everything
           up otherwise it could be doing do_refill in its thread while we are doing
@@ -190,8 +195,19 @@ Session::process_export (pframes_t nframes)
 int
 Session::process_export_fw (pframes_t nframes)
 {
-       if (!_export_started) {
-               _export_started = true;
+       if (_export_preroll > 0) {
+
+               _engine.main_thread()->get_buffers ();
+               fail_roll (nframes);
+               _engine.main_thread()->drop_buffers ();
+
+               _export_preroll -= std::min ((framepos_t)nframes, _export_preroll);
+
+               if (_export_preroll > 0) {
+                       // clear out buffers (reverb tails etc).
+                       return 0;
+               }
+
                set_transport_speed (1.0, 0, false);
                butler_transport_work ();
                g_atomic_int_set (&_butler->should_do_transport_work, 0);
@@ -199,9 +215,9 @@ Session::process_export_fw (pframes_t nframes)
                return 0;
        }
 
-        _engine.main_thread()->get_buffers ();
+       _engine.main_thread()->get_buffers ();
        process_export (nframes);
-        _engine.main_thread()->drop_buffers ();
+       _engine.main_thread()->drop_buffers ();
 
        return 0;
 }