3 files changed, 101 insertions, 3 deletions

diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index 017ea20011..617553129c 100644
--- a/libs/ardour/tempo.cc
+++ b/libs/ardour/tempo.cc
@@ -2118,6 +2118,8 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 
 	frames_per_beat = tempo->frames_per_beat (_frame_rate, *meter);
 
+	double last_dpos = 0;
+
 	while (ddist > 0) {
 
 		/* if we're nearly at the end, but have a fractional beat left,
@@ -2131,6 +2133,7 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 
 		/* walk one beat */
 
+		last_dpos = dpos;
 		ddist -= frames_per_beat;
 		dpos += frames_per_beat;
 		beats += 1.0;
@@ -2140,7 +2143,34 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 		*/
 
 		if (i != metrics->end()) {
-			if ((*i)->frame() <= (framepos_t) dpos) {
+
+			double const f = (*i)->frame ();
+
+			if (f <= (framepos_t) dpos) {
+
+				/* We just went past a tempo/meter section start at (*i)->frame(),
+				   which will be on a beat.
+
+				   So what we have is
+
+				                       (*i)->frame() [f]
+				   beat      beat      beat                beat
+				   |         |         |                   |
+				   |         |         |                   |
+                                                ^         ^
+				                |         |
+						|         new
+						|         dpos [q]
+						last
+						dpos [p]
+
+				  We need to go back to last_dpos (1 beat ago) and re-add
+				  (f - p) beats using the old frames per beat and (q - f) beats
+				  using the new.
+				*/
+
+				beats -= 1;
+				beats += (f - last_dpos) / frames_per_beat;
 
 				if ((t = dynamic_cast<const TempoSection*>(*i)) != 0) {
 					tempo = t;
@@ -2149,6 +2179,8 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 				}
 				++i;
 				frames_per_beat = tempo->frames_per_beat (_frame_rate, *meter);
+
+				beats += (dpos - f) / frames_per_beat;
 			}
 		}
 	}
diff --git a/libs/ardour/test/framewalk_to_beats_test.cc b/libs/ardour/test/framewalk_to_beats_test.cc
index c7fb45cada..c5bd47b62a 100644
--- a/libs/ardour/test/framewalk_to_beats_test.cc
+++ b/libs/ardour/test/framewalk_to_beats_test.cc
@@ -23,11 +23,75 @@ FramewalkToBeatsTest::singleTempoTest ()
 	map.add_meter (meter, BBT_Time (1, 1, 0));
 	map.add_tempo (tempo, BBT_Time (1, 1, 0));
 
-	/* Add 1 beats-worth of frames to a 2 beat starting point */
+	/* Walk 1 beats-worth of frames from beat 3 */
 	double r = map.framewalk_to_beats (frames_per_beat * 2, frames_per_beat * 1);
 	CPPUNIT_ASSERT (r == 1);
 
-	/* Add 6 beats-worth of frames to a 3 beat starting point */
+	/* Walk 6 beats-worth of frames from beat 4 */
 	r = map.framewalk_to_beats (frames_per_beat * 3, frames_per_beat * 6);
 	CPPUNIT_ASSERT (r == 6);
+
+	/* Walk 1.5 beats-worth of frames from beat 3 */
+	r = map.framewalk_to_beats (frames_per_beat * 2, frames_per_beat * 1.5);
+	CPPUNIT_ASSERT (r == 1.5);
+
+	/* Walk 1.5 beats-worth of frames from beat 2.5 */
+	r = map.framewalk_to_beats (frames_per_beat * 2.5, frames_per_beat * 1.5);
+	CPPUNIT_ASSERT (r == 1.5);
 }
+
+void
+FramewalkToBeatsTest::doubleTempoTest ()
+{
+	int const sampling_rate = 48000;
+
+	TempoMap map (sampling_rate);
+	Meter meter (4, 4);
+	map.add_meter (meter, BBT_Time (1, 1, 0));
+
+	/*
+	  120bpm at bar 1, 240bpm at bar 4
+	  
+	  120bpm = 24e3 samples per beat
+	  240bpm = 12e3 samples per beat
+	*/
+	
+
+	/*
+	  
+	  120bpm                                                240bpm
+	  0 beats                                               12 beats
+	  0 frames                                              288e3 frames
+	  |                 |                 |                 |                 |
+	  | 1.1 1.2 1.3 1.4 | 2.1 2.2 2.3.2.4 | 3.1 3.2 3.3 3.4 | 4.1 4.2 4.3 4.4 |
+
+	*/
+
+	Tempo tempoA (120);
+	map.add_tempo (tempoA, BBT_Time (1, 1, 0));
+	Tempo tempoB (240);
+	map.add_tempo (tempoB, BBT_Time (4, 1, 0));
+
+	/* Now some tests */
+
+	/* Walk 1 beat from 1.2 */
+	double r = map.framewalk_to_beats (24e3, 24e3);
+	assert (r == 1);
+
+	/* Walk 2 beats from 3.3 to 4.1 (over the tempo change) */
+	r = map.framewalk_to_beats (264e3, (24e3 + 12e3));
+	assert (r == 2);
+
+	/* Walk 2.5 beats from 3.3-and-a-half to 4.2 (over the tempo change) */
+	r = map.framewalk_to_beats (264e3 - 12e3, (24e3 + 12e3 + 12e3));
+	assert (r == 2.5);
+
+	/* Walk 3 beats from 3.3-and-a-half to 4.2-and-a-half (over the tempo change) */
+	r = map.framewalk_to_beats (264e3 - 12e3, (24e3 + 12e3 + 12e3 + 6e3));
+	assert (r == 3);
+
+	/* Walk 3.5 beats from 3.3-and-a-half to 4.3 (over the tempo change) */
+	r = map.framewalk_to_beats (264e3 - 12e3, (24e3 + 12e3 + 12e3 + 12e3));
+	assert (r == 3.5);
+}
+
diff --git a/libs/ardour/test/framewalk_to_beats_test.h b/libs/ardour/test/framewalk_to_beats_test.h
index 3dd24553e2..ae6ae646eb 100644
--- a/libs/ardour/test/framewalk_to_beats_test.h
+++ b/libs/ardour/test/framewalk_to_beats_test.h
@@ -6,6 +6,7 @@ class FramewalkToBeatsTest : public CppUnit::TestFixture
 {
 	CPPUNIT_TEST_SUITE (FramewalkToBeatsTest);
 	CPPUNIT_TEST (singleTempoTest);
+	CPPUNIT_TEST (doubleTempoTest);
 	CPPUNIT_TEST_SUITE_END ();
 
 public:
@@ -13,5 +14,6 @@ public:
 	void tearDown () {}
 
 	void singleTempoTest ();
+	void doubleTempoTest ();
 };