2 #include <samplerate.h>
4 #include "ardour/types.h"
6 #ifndef __interpolation_h__
7 #define __interpolation_h__
13 double _speed, _target_speed;
15 // the idea is that when the speed is not 1.0, we have to
16 // interpolate between samples and then we have to store where we thought we were.
17 // rather than being at sample N or N+1, we were at N+0.8792922
18 std::vector<double> phase;
22 Interpolation () { _speed = 1.0; _target_speed = 1.0; }
24 void set_speed (double new_speed) { _speed = new_speed; _target_speed = new_speed; }
25 void set_target_speed (double new_speed) { _target_speed = new_speed; }
27 double target_speed() const { return _target_speed; }
28 double speed() const { return _speed; }
30 void add_channel_to (int input_buffer_size, int output_buffer_size) { phase.push_back (0.0); }
31 void remove_channel_from () { phase.pop_back (); }
34 for (size_t i = 0; i <= phase.size(); i++) {
40 // 40.24 fixpoint math
41 #define FIXPOINT_ONE 0x1000000
43 class FixedPointLinearInterpolation : public Interpolation {
45 /// speed in fixed point math
48 /// target speed in fixed point math
51 std::vector<uint64_t> last_phase;
53 // Fixed point is just an integer with an implied scaling factor.
54 // In 40.24 the scaling factor is 2^24 = 16777216,
55 // so a value of 10*2^24 (in integer space) is equivalent to 10.0.
57 // The advantage is that addition and modulus [like x = (x + y) % 2^40]
58 // have no rounding errors and no drift, and just require a single integer add.
61 static const int64_t fractional_part_mask = 0xFFFFFF;
62 static const Sample binary_scaling_factor = 16777216.0f;
66 FixedPointLinearInterpolation () : phi (FIXPOINT_ONE), target_phi (FIXPOINT_ONE) {}
68 void set_speed (double new_speed) {
69 target_phi = (uint64_t) (FIXPOINT_ONE * fabs(new_speed));
73 uint64_t get_phi() { return phi; }
74 uint64_t get_target_phi() { return target_phi; }
75 uint64_t get_last_phase() { assert(last_phase.size()); return last_phase[0]; }
76 void set_last_phase(uint64_t phase) { assert(last_phase.size()); last_phase[0] = phase; }
78 void add_channel_to (int input_buffer_size, int output_buffer_size);
79 void remove_channel_from ();
81 nframes_t interpolate (int channel, nframes_t nframes, Sample* input, Sample* output);
85 class LinearInterpolation : public Interpolation {
89 nframes_t interpolate (int channel, nframes_t nframes, Sample* input, Sample* output);
93 #define MAX_PERIOD_SIZE 4096
95 * @class SplineInterpolation
97 * @brief interpolates using cubic spline interpolation over an input period
99 * Splines are piecewise cubic functions between each samples,
100 * where the cubic polynomials' values, first and second derivatives are equal
101 * on each sample point.
103 * Those conditions are equivalent of solving the linear system of equations
104 * defined by the matrix equation (all indices are zero-based):
107 * where A has (n-2) rows and (n-2) columns
109 * [ 4 1 0 0 ... 0 0 0 0 ] [ M[1] ] [ 6*y[0] - 12*y[1] + 6*y[2] ]
110 * [ 1 4 1 0 ... 0 0 0 0 ] [ M[2] ] [ 6*y[1] - 12*y[2] + 6*y[3] ]
111 * [ 0 1 4 1 ... 0 0 0 0 ] [ M[3] ] [ 6*y[2] - 12*y[3] + 6*y[4] ]
112 * [ 0 0 1 4 ... 0 0 0 0 ] [ M[4] ] [ 6*y[3] - 12*y[4] + 6*y[5] ]
114 * [ 0 0 0 0 ... 4 1 0 0 ] [ M[n-5] ] [ 6*y[n-6]- 12*y[n-5] + 6*y[n-4] ]
115 * [ 0 0 0 0 ... 1 4 1 0 ] [ M[n-4] ] [ 6*y[n-5]- 12*y[n-4] + 6*y[n-3] ]
116 * [ 0 0 0 0 ... 0 1 4 1 ] [ M[n-3] ] [ 6*y[n-4]- 12*y[n-3] + 6*y[n-2] ]
117 * [ 0 0 0 0 ... 0 0 1 4 ] [ M[n-2] ] [ 6*y[n-3]- 12*y[n-2] + 6*y[n-1] ]
119 * For our purpose we use natural splines which means the boundary coefficients
122 * The interpolation polynomial in the i-th interval then has the form
123 * p_i(x) = a3 (x - i)^3 + a2 (x - i)^2 + a1 (x - i) + a0
124 * = ((a3 * (x - i) + a2) * (x - i) + a1) * (x - i) + a0
126 * a3 = (M[i+1] - M[i]) / 6
128 * a1 = y[i+1] - y[i] - M[i+1]/6 - M[i]/3
131 * We solve the system by LU-factoring the matrix A:
134 * [ 4 1 0 0 ... 0 0 0 0 ] [ 1 0 0 0 ... 0 0 0 0 ] [ m[0] 1 0 0 ... 0 0 0 ]
135 * [ 1 4 1 0 ... 0 0 0 0 ] [ l[0] 1 0 0 ... 0 0 0 0 ] [ 0 m[1] 1 0 ... 0 0 0 ]
136 * [ 0 1 4 1 ... 0 0 0 0 ] [ 0 l[1] 1 0 ... 0 0 0 0 ] [ 0 0 m[2] 1 ... 0 0 0 ]
137 * [ 0 0 1 4 ... 0 0 0 0 ] [ 0 0 l[2] 1 ... 0 0 0 0 ] ...
138 * ... = ... * [ 0 0 0 0 ... 0 0 0 ]
139 * [ 0 0 0 0 ... 4 1 0 0 ] [ 0 0 0 0 ... 1 0 0 0 ] [ 0 0 0 0 ... 1 0 0 ]
140 * [ 0 0 0 0 ... 1 4 1 0 ] [ 0 0 0 0 ... l[n-6] 1 0 0 ] [ 0 0 0 0 ... m[n-5] 1 0 ]
141 * [ 0 0 0 0 ... 0 1 4 1 ] [ 0 0 0 0 ... 0 l[n-5] 1 0 ] [ 0 0 0 0 ... 0 m[n-4] 1 ]
142 * [ 0 0 0 0 ... 0 0 1 4 ] [ 0 0 0 0 ... 0 0 l[n-4] 1 ] [ 0 0 0 0 ... 0 0 m[n-3] ]
144 * where the l[i] and m[i] can be precomputed.
146 * Then we solve the system A * M = d by first solving the system
151 class SplineInterpolation : public Interpolation {
153 double l[MAX_PERIOD_SIZE], m[MAX_PERIOD_SIZE];
156 SplineInterpolation();
157 nframes_t interpolate (int channel, nframes_t nframes, Sample* input, Sample* output);
160 class LibSamplerateInterpolation : public Interpolation {
162 std::vector<SRC_STATE*> state;
163 std::vector<SRC_DATA*> data;
170 LibSamplerateInterpolation ();
171 ~LibSamplerateInterpolation ();
173 void set_speed (double new_speed);
174 void set_target_speed (double new_speed) {}
175 double speed () const { return _speed; }
177 void add_channel_to (int input_buffer_size, int output_buffer_size);
178 void remove_channel_from ();
180 nframes_t interpolate (int channel, nframes_t nframes, Sample* input, Sample* output);
181 void reset() { reset_state (); }
184 } // namespace ARDOUR