Move all beats <-> frames time conversion into a single object that can be passed around.

This has 3 main benefits:
 - All conversion code is in one place (less duplication, potential bugs)
 - The conversion method can be passed to things that are ignorant
   of the actual time units involved, information required, etc.
   (In the future it would be nice to have user selectable tempo/frame time)
 - It should be relatively simple now to support tempo changes part-way
   through a MIDI region (at least architecturally speaking)


git-svn-id: svn://localhost/ardour2/branches/3.0@4594 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 54 insertions, 0 deletions

diff --git a/libs/ardour/beats_frames_converter.cc b/libs/ardour/beats_frames_converter.cc
new file mode 100644
index 0000000000..736068e690
--- /dev/null
+++ b/libs/ardour/beats_frames_converter.cc
@@ -0,0 +1,54 @@
+/*
+    Copyright (C) 2009 Paul Davis 
+    Author: Dave Robillard
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+    $Id: midiregion.h 733 2006-08-01 17:19:38Z drobilla $
+*/
+
+#include <ardour/audioengine.h>
+#include <ardour/beats_frames_converter.h>
+#include <ardour/session.h>
+#include <ardour/tempo.h>
+
+namespace ARDOUR {
+
+nframes_t
+BeatsFramesConverter::to(double beats) const
+{
+	// FIXME: assumes tempo never changes after origin
+	const Tempo& tempo = _session.tempo_map().tempo_at(_origin);
+	const double frames_per_beat = tempo.frames_per_beat(
+			_session.engine().frame_rate(),
+			_session.tempo_map().meter_at(_origin));
+
+	return lrint(beats * frames_per_beat);
+}
+
+double
+BeatsFramesConverter::from(nframes_t frames) const
+{
+	// FIXME: assumes tempo never changes after origin
+	const Tempo& tempo = _session.tempo_map().tempo_at(_origin);
+	const double frames_per_beat = tempo.frames_per_beat(
+			_session.engine().frame_rate(),
+			_session.tempo_map().meter_at(_origin));
+
+	return frames / frames_per_beat;
+}
+
+} /* namespace ARDOUR */
+