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Fix duration and bitrate calculation of MP3 files via XING header 

* Calculate the duration independently of the bitrate which is supposedly
  more accurate
* Fix conversion factor for computing bitrate
* Use real size if it differs from size specified in Xing header; this way
  the bitrate is consistent with MediaInfo and other tools (there is
  possibly still a bug in the way the size is read from the Xing header,
  though)
This commit is contained in:
Martchus 2023-08-21 12:09:07 +02:00
parent f2e97b9899
commit 0827002183
1 changed files with 15 additions and 10 deletions
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25
mpegaudio/mpegaudioframestream.cpp
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@ -68,19 +68,24 @@ void MpegAudioFrameStream::internalParseHeader(Diagnostics &diag, AbortableProgr
const MpegAudioFrame &frame = m_frames.back();
addInfo(frame, *this);
if (frame.isXingBytesfieldPresent()) {
std::uint32_t xingSize = frame.xingBytesfield();
if (m_size && xingSize != m_size) {
diag.emplace_back(DiagLevel::Warning,
argsToString("Real length of MPEG audio frames (", m_size, " byte) is not in accordance with value provided by Xing header (",
xingSize, " byte). The Xing header value will be used."),
context);
const auto xingSize = frame.xingBytesfield();
if (!m_size) {
m_size = xingSize;
} else if (xingSize != m_size) {
diag.emplace_back(DiagLevel::Warning,
argsToString("Real size of MPEG audio frames (", m_size, " byte) is not in accordance with value provided by Xing header (", xingSize,
" byte). The real size will be used."),
context);
}
}
m_bitrate = frame.isXingFramefieldPresent() ? ((static_cast<double>(m_size) * 8.0)
/ (static_cast<double>(frame.xingFrameCount() * frame.sampleCount()) / static_cast<double>(frame.samplingFrequency())) / 1024.0)
: frame.bitrate();
m_duration = TimeSpan::fromSeconds(static_cast<double>(m_size) / (m_bytesPerSecond = static_cast<std::uint32_t>(m_bitrate * 125)));
if (frame.isXingFramefieldPresent()) {
const auto duration = static_cast<double>(frame.xingFrameCount() * frame.sampleCount()) / static_cast<double>(frame.samplingFrequency());
m_bitrate = static_cast<double>(m_size) / duration / 125.0;
m_duration = TimeSpan::fromSeconds(duration);
} else {
m_bitrate = frame.bitrate();
m_duration = TimeSpan::fromSeconds(static_cast<double>(m_size) / (m_bytesPerSecond = static_cast<std::uint32_t>(m_bitrate * 125)));
}
}
} // namespace TagParser