libardour: * Add basic classes for later support of multiple interpolation algorithms for varispeed

                * Add unit tests: Test which shows how the varispeed implementation in diskstream is broken.

git-svn-id: svn://localhost/ardour2/branches/3.0@5144 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 49 insertions, 0 deletions

diff --git a/libs/ardour/ardour/interpolation.h b/libs/ardour/ardour/interpolation.h
new file mode 100644
index 0000000000..09ae242490
--- /dev/null
+++ b/libs/ardour/ardour/interpolation.h
@@ -0,0 +1,49 @@
+#include <math.h>
+//#include "ardour/types.h"
+
+typedef float Sample;
+#define nframes_t uint32_t
+
+// 40.24 fixpoint math
+#define FIXPOINT_ONE 0x1000000
+
+class Interpolation {
+    protected:
+    /// speed in fixed point math
+    uint64_t      phi;
+    
+    /// target speed in fixed point math
+    uint64_t      target_phi;
+    
+    uint64_t      last_phase;
+
+	// Fixed point is just an integer with an implied scaling factor. 
+	// In 40.24 the scaling factor is 2^24 = 16777216,  
+	// so a value of 10*2^24 (in integer space) is equivalent to 10.0. 
+	//
+	// The advantage is that addition and modulus [like x = (x + y) % 2^40]  
+	// have no rounding errors and no drift, and just require a single integer add.
+	// (swh)
+	
+	static const int64_t fractional_part_mask  = 0xFFFFFF;
+	static const Sample  binary_scaling_factor = 16777216.0f;
+    
+    public:
+        Interpolation () : phi (FIXPOINT_ONE), target_phi (FIXPOINT_ONE), last_phase (0) {}
+    
+        void set_speed (double new_speed) {
+            target_phi = (uint64_t) (FIXPOINT_ONE * fabs(new_speed));
+            phi = target_phi;
+        }
+        
+        uint64_t get_phi () const { return phi; }
+        uint64_t get_target_phi () const { return target_phi; }
+        uint64_t get_last_phase () const { return last_phase; }
+ 
+        virtual nframes_t interpolate (nframes_t nframes, Sample* input, Sample* output) = 0;
+};
+
+class LinearInterpolation : public Interpolation {
+    public:
+        nframes_t interpolate (nframes_t nframes, Sample* input, Sample* output);
+};