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/*
* Copyright 2023 jacqueline <me@jacqueline.id.au>
*
* SPDX-License-Identifier: GPL-3.0-only
*/
#include "resample.hpp"
/*
* This file contains the implementation for a 32-bit floating point resampler.
* It is largely based on David Bryant's ART resampler, which is BSD-licensed,
* and available at https://github.com/dbry/audio-resampler/.
*
* This resampler uses windowed sinc interpolation filters, with an additional
* lowpass filter to reduce aliasing.
*/
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <algorithm>
#include <cmath>
#include <numeric>
#include "esp_log.h"
#include "sample.hpp"
#include "speex/speex_resampler.h"
#include "stream_info.hpp"
namespace audio {
static constexpr int kQuality = SPEEX_RESAMPLER_QUALITY_MIN;
Resampler::Resampler(uint32_t source_sample_rate,
uint32_t target_sample_rate,
uint8_t num_channels)
: err_(0),
resampler_(speex_resampler_init(num_channels,
source_sample_rate,
target_sample_rate,
kQuality,
&err_)),
num_channels_(num_channels) {
assert(err_ == 0);
}
Resampler::~Resampler() {
speex_resampler_destroy(resampler_);
}
auto Resampler::Process(cpp::span<sample::Sample> input,
cpp::span<sample::Sample> output,
bool end_of_data) -> std::pair<size_t, size_t> {
uint32_t samples_used = input.size() / num_channels_;
uint32_t samples_produced = output.size() / num_channels_;
int err = speex_resampler_process_interleaved_int(
resampler_, input.data(), &samples_used, output.data(),
&samples_produced);
assert(err == 0);
return {samples_used * num_channels_, samples_produced * num_channels_};
}
} // namespace audio
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