From 45b1f6f6b8de94c90f0fb93a18062d02fdb62ca9 Mon Sep 17 00:00:00 2001 From: Paul Davis Date: Mon, 2 Oct 2017 12:42:44 -0400 Subject: change API and implementation for CubicInterpolation and Interpolation. Also remove LinearInterpolation which is not used --- libs/ardour/interpolation.cc | 274 ++++++++++++++++++++++++++----------------- 1 file changed, 166 insertions(+), 108 deletions(-) (limited to 'libs/ardour/interpolation.cc') diff --git a/libs/ardour/interpolation.cc b/libs/ardour/interpolation.cc index 8d45c66a75..c29a62232b 100644 --- a/libs/ardour/interpolation.cc +++ b/libs/ardour/interpolation.cc @@ -17,151 +17,209 @@ */ -#include +#include #include +#include + #include "ardour/interpolation.h" #include "ardour/midi_buffer.h" using namespace ARDOUR; +using std::cerr; +using std::endl; +CubicInterpolation::CubicInterpolation () + : valid_z_bits (0) +{ +} samplecnt_t -LinearInterpolation::interpolate (int channel, samplecnt_t nframes, Sample *input, Sample *output) +CubicInterpolation::interpolate (int channel, samplecnt_t input_samples, Sample *input, samplecnt_t & output_samples, Sample *output) { - // index in the input buffers - samplecnt_t i = 0; + assert (input_samples > 0); + assert (output_samples > 0); + assert (input); + assert (output); - double acceleration = 0; + _speed = fabs (_speed); - if (_speed != _target_speed) { - acceleration = _target_speed - _speed; - } + if (invalid (0)) { - for (samplecnt_t outsample = 0; outsample < nframes; ++outsample) { - double const d = phase[channel] + outsample * (_speed + acceleration); - i = floor(d); - Sample fractional_phase_part = d - i; - if (fractional_phase_part >= 1.0) { - fractional_phase_part -= 1.0; - i++; - } + /* z[0] not set. Two possibilities + * + * 1) we have just been constructed or ::reset() + * + * 2) we were only given 1 sample after construction or + * ::reset, and stored it in z[1] + */ - if (input && output) { - // Linearly interpolate into the output buffer - output[outsample] = - input[i] * (1.0f - fractional_phase_part) + - input[i+1] * fractional_phase_part; - } - } + if (invalid (1)) { + + /* first call after construction or after ::reset */ + + switch (input_samples) { + case 1: + /* store one sample for use next time. We don't + * have enough points to interpolate or even + * compute the first z[0] value, but keep z[1] + * around. + */ + z[1] = input[0]; validate (1); + output_samples = 0; + return 0; + case 2: + /* store two samples for use next time, and + * compute a value for z[0] that will maintain + * the slope of the first actual segment. We + * still don't have enough samples to interpolate. + */ + z[0] = input[0] - (input[1] - input[0]); validate (0); + z[1] = input[0]; validate (1); + z[2] = input[1]; validate (2); + output_samples = 0; + return 0; + default: + /* We have enough samples to interpolate this time, + * but don't have a valid z[0] value because this is the + * first call after construction or ::reset. + * + * First point is based on a requirement to maintain + * the slope of the first actual segment + */ + z[0] = input[0] - (input[1] - input[0]); validate (0); + break; + } + } else { - double const distance = phase[channel] + nframes * (_speed + acceleration); - i = floor(distance); - phase[channel] = distance - i; - return i; -} + /* at least one call since construction or + * after::reset, since we have z[1] set + * + * we can now compute z[0] as required + */ -samplecnt_t -CubicInterpolation::interpolate (int channel, samplecnt_t nframes, Sample *input, Sample *output) -{ - // index in the input buffers - samplecnt_t i = 0; + z[0] = z[1] - (input[0] - z[1]); validate (0); - double acceleration; - double distance = phase[channel]; + /* we'll check the number of samples we've been given + in the next switch() statement below, and either + just save some more samples or actual interpolate + */ + } - if (_speed != _target_speed) { - acceleration = _target_speed - _speed; - } else { - acceleration = 0.0; + assert (is_valid (0)); } - if (nframes < 3) { - /* no interpolation possible */ - - if (input && output) { - for (i = 0; i < nframes; ++i) { - output[i] = input[i]; - } + switch (input_samples) { + case 1: + /* one more sample of input. find the right vX to store + it in, and decide if we're ready to interpolate + */ + if (invalid (1)) { + z[1] = input[0]; validate (1); + /* still not ready to interpolate */ + output_samples = 0; + return 0; + } else if (invalid (2)) { + /* still not ready to interpolate */ + z[2] = input[0]; validate (2); + output_samples = 0; + return 0; + } else if (invalid (3)) { + z[3] = input[0]; validate (3); + /* ready to interpolate */ } - - phase[channel] = 0; - return nframes; + break; + case 2: + /* two more samples of input. find the right vX to store + them in, and decide if we're ready to interpolate + */ + if (invalid (1)) { + z[1] = input[0]; validate (1); + z[2] = input[1]; validate (2); + /* still not ready to interpolate */ + output_samples = 0; + return 0; + } else if (invalid (2)) { + z[2] = input[0]; validate (2); + z[3] = input[1]; validate (3); + /* ready to interpolate */ + } else if (invalid (3)) { + z[3] = input[0]; validate (3); + /* ready to interpolate */ + } + break; + + default: + /* caller has given us at least enough samples to interpolate a + single value. + */ + z[1] = input[0]; validate (1); + z[2] = input[1]; validate (2); + z[3] = input[2]; validate (3); } - /* keep this condition out of the inner loop */ + /* ready to interpolate using z[0], z[1], z[2] and z[3] */ - if (input && output) { - /* best guess for the fake point we have to add to be able to interpolate at i == 0: - * .... maintain slope of first actual segment ... - */ - Sample inm1 = input[i] - (input[i+1] - input[i]); - - for (samplecnt_t outsample = 0; outsample < nframes; ++outsample) { - /* get the index into the input we should start with */ - i = floor (distance); - float fractional_phase_part = fmod (distance, 1.0); + assert (is_valid (0)); + assert (is_valid (1)); + assert (is_valid (2)); + assert (is_valid (3)); - // Cubically interpolate into the output buffer: keep this inlined for speed and rely on compiler - // optimization to take care of the rest - // shamelessly ripped from Steve Harris' swh-plugins (ladspa-util.h) + /* we can use up to (input_samples - 2) of the input, so compute the + * maximum number of output samples that represents. + * + * Remember that the expected common case here is to be given + * input_samples that is substantially larger than output_samples, + * thus allowing us to always compute output_samples in one call. + */ - output[outsample] = input[i] + 0.5f * fractional_phase_part * (input[i+1] - inm1 + - fractional_phase_part * (4.0f * input[i+1] + 2.0f * inm1 - 5.0f * input[i] - input[i+2] + - fractional_phase_part * (3.0f * (input[i] - input[i+1]) - inm1 + input[i+2]))); + const samplecnt_t output_from_input = floor ((input_samples - 2) / _speed); - distance += _speed + acceleration; - inm1 = input[i]; - } + /* limit output to either the caller's requested number or the number + * determined by the input size. + */ - i = floor (distance); - phase[channel] = fmod (distance, 1.0); + const samplecnt_t limit = std::min (output_samples, output_from_input); - } else { - /* used to calculate play-distance with acceleration (silent roll) - * (use same algorithm as real playback for identical rounding/floor'ing) - */ - for (samplecnt_t outsample = 0; outsample < nframes; ++outsample) { - distance += _speed + acceleration; - } - i = floor (distance); - phase[channel] = fmod (distance, 1.0); - } + samplecnt_t outsample = 0; + double distance = phase[channel]; + samplecnt_t used = floor (distance); + samplecnt_t i = 0; - return i; -} + while (outsample < limit) { -/* CubicMidiInterpolation::distance is identical to - * return CubicInterpolation::interpolate (0, nframes, NULL, NULL); - */ -samplecnt_t -CubicMidiInterpolation::distance (samplecnt_t nframes, bool /*roll*/) -{ - assert (phase.size () == 1); + i = floor (distance); - samplecnt_t i = 0; + /* this call may stop the loop from being vectorized */ + float fractional_phase_part = fmod (distance, 1.0); - double acceleration; - double distance = phase[0]; + /* Cubically interpolate into the output buffer */ + output[outsample++] = z[1] + 0.5f * fractional_phase_part * + (z[2] - z[0] + fractional_phase_part * (4.0f * z[2] + 2.0f * z[0] - 5.0f * z[1] - z[3] + + fractional_phase_part * (3.0f * (z[1] - z[2]) - z[0] + z[3]))); - if (nframes < 3) { - /* no interpolation possible */ - phase[0] = 0; - return nframes; - } + distance += _speed; - if (_speed != _target_speed) { - acceleration = _target_speed - _speed; - } else { - acceleration = 0.0; + z[0] = z[1]; + z[1] = input[i]; + z[2] = input[i+1]; + z[3] = input[i+2]; } - for (samplecnt_t outsample = 0; outsample < nframes; ++outsample) { - distance += _speed + acceleration; - } + output_samples = outsample; + phase[channel] = fmod (distance, 1.0); + return i - used; +} - i = floor (distance); - phase[0] = fmod (distance, 1.0); +void +CubicInterpolation::reset () +{ + Interpolation::reset (); + valid_z_bits = 0; +} - return i; +samplecnt_t +CubicInterpolation::distance (samplecnt_t nsamples) +{ + return floor (floor (phase[0]) + (_speed * nsamples)); } -- cgit v1.2.3