load_opus.cpp

#include "load_opus.hpp"

#include <opusfile.h>

#include <cassert>
#include <memory>
#include <cmath>
#include <stdexcept>
#include <iostream>

void load_opus(std::string const &filename, std::vector< float > *data_) {
	assert(data_);
	auto &data = *data_;
	data.clear();

	std::cout << "loading '" << filename << "'..."; std::cout.flush();

	//will hold opusfile * int a std::unique_ptr so that it will automatically be deleted:
	int err = 0;
	std::unique_ptr< OggOpusFile, decltype(&op_free) > op(
		op_open_file(filename.c_str(), &err), //pointer to hold
		op_free //deletion function
	);
	if (err != 0) {
		throw std::runtime_error("opusfile error " + std::to_string(err) + " opening \"" + filename + "\".");
	}

	//get length in samples:
	ogg_int64_t length = op_pcm_total(op.get(), -1);
	if (length >= 0) {
		data.reserve(length);
	} else {
		std::cerr << "WARNING: cannot estimate length of '" << filename << "', loading may be slow." << std::endl;
		length = 0;
		data.reserve(2*48000);
	}

	std::vector< float > pcm(2*48000*2, 0.0f); //seems like reads are generally 960 samples so this is definitely overkill
	for (;;) {
		int ret = op_read_float_stereo(op.get(), pcm.data(), int(pcm.size()));
		if (ret >= 0) {
			//positive return values are the number of samples read per channel; copy into data:
			data.reserve(data.size() + ret);
			for (uint32_t i = 0; i < uint32_t(ret); ++i) {
				data.emplace_back((pcm[2*i] + pcm[2*i+1]) * 0.5f); //downmix to mono by averaging
			}
			if (ret == 0) break;
		} else {
			throw std::runtime_error("opusfile read error " + std::to_string(ret) + " reading \"" + filename + "\".");
		}
	}

	std::cout << " done." << std::endl;
}