| /* |
| * Rational Sample Rate Conversion |
| * Copyright (C) 2012, 2013 Thomas Tsou <tom@tsou.cc> |
| * |
| * This library is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * This library 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 |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with this library; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include <stdlib.h> |
| #include <math.h> |
| #include <string.h> |
| #include <malloc.h> |
| #include <iostream> |
| #include <algorithm> |
| |
| #include "Resampler.h" |
| |
| extern "C" { |
| #include "convolve.h" |
| } |
| |
| #ifndef M_PI |
| #define M_PI 3.14159265358979323846264338327f |
| #endif |
| |
| #define MAX_OUTPUT_LEN 4096 |
| |
| using namespace std; |
| |
| static float sinc(float x) |
| { |
| if (x == 0.0) |
| return 0.9999999999; |
| |
| return sin(M_PI * x) / (M_PI * x); |
| } |
| |
| void Resampler::initFilters(float bw) |
| { |
| float cutoff; |
| float sum = 0.0f, scale = 0.0f; |
| |
| /* |
| * Allocate partition filters and the temporary prototype filter |
| * according to numerator of the rational rate. Coefficients are |
| * real only and must be 16-byte memory aligned for SSE usage. |
| */ |
| auto proto = vector<float>(p * filt_len); |
| for (auto &part : partitions) |
| part = (complex<float> *) memalign(16, filt_len * sizeof(complex<float>)); |
| |
| /* |
| * Generate the prototype filter with a Blackman-harris window. |
| * Scale coefficients with DC filter gain set to unity divided |
| * by the number of filter partitions. |
| */ |
| float a0 = 0.35875; |
| float a1 = 0.48829; |
| float a2 = 0.14128; |
| float a3 = 0.01168; |
| |
| if (p > q) |
| cutoff = (float) p; |
| else |
| cutoff = (float) q; |
| |
| float midpt = (proto.size() - 1) / 2.0; |
| for (size_t i = 0; i < proto.size(); i++) { |
| proto[i] = sinc(((float) i - midpt) / cutoff * bw); |
| proto[i] *= a0 - |
| a1 * cos(2 * M_PI * i / (proto.size() - 1)) + |
| a2 * cos(4 * M_PI * i / (proto.size() - 1)) - |
| a3 * cos(6 * M_PI * i / (proto.size() - 1)); |
| sum += proto[i]; |
| } |
| scale = p / sum; |
| |
| /* Populate filter partitions from the prototype filter */ |
| for (size_t i = 0; i < filt_len; i++) { |
| for (size_t n = 0; n < p; n++) |
| partitions[n][i] = complex<float>(proto[i * p + n] * scale); |
| } |
| |
| /* Store filter taps in reverse */ |
| for (auto &part : partitions) |
| reverse(&part[0], &part[filt_len]); |
| } |
| |
| static bool check_vec_len(int in_len, int out_len, int p, int q) |
| { |
| if (in_len % q) { |
| std::cerr << "Invalid input length " << in_len |
| << " is not multiple of " << q << std::endl; |
| return false; |
| } |
| |
| if (out_len % p) { |
| std::cerr << "Invalid output length " << out_len |
| << " is not multiple of " << p << std::endl; |
| return false; |
| } |
| |
| if ((in_len / q) != (out_len / p)) { |
| std::cerr << "Input/output block length mismatch" << std::endl; |
| std::cerr << "P = " << p << ", Q = " << q << std::endl; |
| std::cerr << "Input len: " << in_len << std::endl; |
| std::cerr << "Output len: " << out_len << std::endl; |
| return false; |
| } |
| |
| if (out_len > MAX_OUTPUT_LEN) { |
| std::cerr << "Block length of " << out_len |
| << " exceeds max of " << MAX_OUTPUT_LEN << std::endl; |
| return false; |
| } |
| |
| return true; |
| } |
| |
| int Resampler::rotate(const float *in, size_t in_len, float *out, size_t out_len) |
| { |
| int n, path; |
| |
| if (!check_vec_len(in_len, out_len, p, q)) |
| return -1; |
| |
| /* Generate output from precomputed input/output paths */ |
| for (size_t i = 0; i < out_len; i++) { |
| n = in_index[i]; |
| path = out_path[i]; |
| |
| convolve_real(in, in_len, |
| reinterpret_cast<float *>(partitions[path]), |
| filt_len, &out[2 * i], out_len - i, |
| n, 1, 1, 0); |
| } |
| |
| return out_len; |
| } |
| |
| bool Resampler::init(float bw) |
| { |
| if (p == 0 || q == 0 || filt_len == 0) return false; |
| |
| /* Filterbank filter internals */ |
| initFilters(bw); |
| |
| /* Precompute filterbank paths */ |
| int i = 0; |
| for (auto &index : in_index) |
| index = (q * i++) / p; |
| i = 0; |
| for (auto &path : out_path) |
| path = (q * i++) % p; |
| |
| return true; |
| } |
| |
| size_t Resampler::len() |
| { |
| return filt_len; |
| } |
| |
| Resampler::Resampler(size_t p, size_t q, size_t filt_len) |
| : in_index(MAX_OUTPUT_LEN), out_path(MAX_OUTPUT_LEN), partitions(p) |
| { |
| this->p = p; |
| this->q = q; |
| this->filt_len = filt_len; |
| } |
| |
| Resampler::~Resampler() |
| { |
| for (auto &part : partitions) |
| free(part); |
| } |