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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*!********************************************************************
Audacity: A Digital Audio Editor
Mp3FileReader.cpp
Matthieu Hodgkinson
**********************************************************************/
#include "Mp3FileReader.h"
#include "AudioFileInfo.h"
#include <mpg123.h>
bool Mp3FileReader::Read(
const std::string& path, std::vector<std::vector<float>>& floats,
AudioFileInfo& info)
{
int error = MPG123_OK;
mpg123_handle* handle = mpg123_new(nullptr, &error);
if (handle == nullptr)
return false;
if (mpg123_open(handle, path.c_str()) != MPG123_OK)
return false;
mpg123_param(handle, MPG123_FLAGS, MPG123_GAPLESS | MPG123_FORCE_FLOAT, 0.0);
if (mpg123_scan(handle) != MPG123_OK)
return false;
if (
mpg123_decode_frame(handle, nullptr, nullptr, nullptr) !=
MPG123_NEW_FORMAT)
return false;
long long framesCount = mpg123_framelength(handle);
long rate;
int channels;
int encoding = MPG123_ENC_FLOAT_32;
mpg123_getformat(handle, &rate, &channels, &encoding);
const auto numChannels = channels == MPG123_MONO ? 1 : 2;
if (encoding != MPG123_ENC_FLOAT_32)
return false;
floats.resize(numChannels);
off_t frameIndex { 0 };
unsigned char* data { nullptr };
size_t dataSize { 0 };
std::vector<float> conversionBuffer;
int ret = MPG123_OK;
while ((ret = mpg123_decode_frame(handle, &frameIndex, &data, &dataSize)) ==
MPG123_OK)
for (auto channelIndex = 0; channelIndex < numChannels; ++channelIndex)
for (auto frameIndex = 0;
frameIndex < dataSize / numChannels / sizeof(float); ++frameIndex)
{
const auto floatIndex = channelIndex + frameIndex * numChannels;
const auto value =
*reinterpret_cast<float*>(data + floatIndex * sizeof(float));
floats[channelIndex].push_back(value);
}
mpg123_close(handle);
mpg123_delete(handle);
mpg123_exit();
info.sampleRate = rate;
info.numChannels = numChannels;
info.numFrames = floats[0].size();
return true;
}
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