Tag Parser  10.0.0
C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags
mpegaudioframestream.cpp
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2 
3 #include "../exceptions.h"
4 #include "../mediaformat.h"
5 
6 #include <sstream>
7 
8 using namespace std;
9 using namespace CppUtilities;
10 
11 namespace TagParser {
12 
21 void MpegAudioFrameStream::addInfo(const MpegAudioFrame &frame, AbstractTrack &track)
22 {
23  track.m_version = frame.mpegVersion();
24  track.m_format = MediaFormat(GeneralMediaFormat::Mpeg1Audio, static_cast<unsigned char>(frame.layer()));
25  track.m_channelCount = frame.channelMode() == MpegChannelMode::SingleChannel ? 1 : 2;
26  track.m_channelConfig = static_cast<std::uint8_t>(frame.channelMode());
27  track.m_samplingFrequency = frame.samplingFrequency();
28 }
29 
30 void MpegAudioFrameStream::internalParseHeader(Diagnostics &diag, AbortableProgressFeedback &progress)
31 {
32  CPP_UTILITIES_UNUSED(progress)
33 
34  static const string context("parsing MPEG audio frame header");
35  if (!m_istream) {
36  throw NoDataFoundException();
37  }
38  // get size
39  m_istream->seekg(-128, ios_base::end);
40  if (m_reader.readUInt24BE() == 0x544147) {
41  m_size = static_cast<std::uint64_t>(m_istream->tellg()) - 3u - m_startOffset;
42  } else {
43  m_size = static_cast<std::uint64_t>(m_istream->tellg()) + 125u - m_startOffset;
44  }
45  m_istream->seekg(static_cast<streamoff>(m_startOffset), ios_base::beg);
46  // parse frames until the first valid, non-empty frame is reached
47  for (size_t invalidByteskipped = 0; m_frames.size() < 200 && invalidByteskipped <= 0x600u;) {
48  MpegAudioFrame &frame = invalidByteskipped > 0 ? m_frames.back() : m_frames.emplace_back();
49  try {
50  frame.parseHeader(m_reader, diag);
51  } catch (const InvalidDataException &e) {
52  if (++invalidByteskipped > 1) {
53  diag.pop_back();
54  }
55  m_istream->seekg(-3, ios_base::cur);
56  continue;
57  }
58  if (invalidByteskipped > 1) {
59  diag.emplace_back(DiagLevel::Critical, argsToString("The next ", invalidByteskipped, " bytes are junk as well."), context);
60  }
61  if (!frame.size()) {
62  continue; // likely just junk, check further frames
63  }
64  invalidByteskipped = 0;
65  if (frame.isProtectedByCrc()) {
66  m_istream->seekg(2, ios_base::cur);
67  }
68  break;
69  }
70  if (!m_frames.back().isValid()) {
71  return;
72  }
73  const MpegAudioFrame &frame = m_frames.back();
74  addInfo(frame, *this);
75  if (frame.isXingBytesfieldPresent()) {
76  std::uint32_t xingSize = frame.xingBytesfield();
77  if (m_size && xingSize != m_size) {
78  diag.emplace_back(DiagLevel::Warning,
79  "Real length of MPEG audio frames is not in accordance with value provided by Xing header. The Xing header value will be used.",
80  context);
81  m_size = xingSize;
82  }
83  }
84  m_bitrate = frame.isXingFramefieldPresent() ? ((static_cast<double>(m_size) * 8.0)
85  / (static_cast<double>(frame.xingFrameCount() * frame.sampleCount()) / static_cast<double>(frame.samplingFrequency())) / 1024.0)
86  : frame.bitrate();
87  m_duration = TimeSpan::fromSeconds(static_cast<double>(m_size) / (m_bytesPerSecond = static_cast<std::uint32_t>(m_bitrate * 125)));
88 }
89 
90 } // namespace TagParser
The AbortableProgressFeedback class provides feedback about an ongoing operation via callbacks.
The AbstractTrack class parses and stores technical information about video, audio and other kinds of...
Definition: abstracttrack.h:65
std::uint16_t m_channelCount
std::uint8_t m_channelConfig
std::uint32_t m_samplingFrequency
The Diagnostics class is a container for DiagMessage.
Definition: diagnostics.h:156
The exception that is thrown when the data to be parsed or to be made seems invalid and therefore can...
Definition: exceptions.h:25
The MediaFormat class specifies the format of media data.
Definition: mediaformat.h:246
The MpegAudioFrame class is used to parse MPEG audio frames.
std::uint32_t size() const
Returns the size if known; otherwise retruns 0.
std::uint32_t samplingFrequency() const
Returns the sampeling frequency of the frame if known; otherwise returns 0.
MpegChannelMode channelMode() const
Returns the channel mode if known; otherwise returns MpegChannelMode::Unspecifed.
constexpr bool isProtectedByCrc() const
Returns an indication whether the frame is protected by CRC.
std::uint32_t sampleCount() const
Returns the sample count if known; otherwise returns 0.
int layer() const
Returns the MPEG layer if known (1, 2, or 3); otherwise returns 0.
std::uint16_t bitrate() const
Returns the bitrate of the frame if known; otherwise returns 0.
constexpr std::uint32_t xingFrameCount() const
Returns an indication whether the Xing frame count is present.
constexpr bool isXingBytesfieldPresent() const
Returns an indication whether the Xing bytes field is present.
void parseHeader(CppUtilities::BinaryReader &reader, Diagnostics &diag)
Parses the header read using the specified reader.
double mpegVersion() const
Returns the MPEG version if known (1.0, 2.0 or 2.5); otherwise returns 0.
constexpr bool isXingFramefieldPresent() const
Returns an indication whether the Xing frame field is present.
constexpr std::uint32_t xingBytesfield() const
Returns the Xing bytes field if known; otherwise returns 0.
The exception that is thrown when the data to be parsed holds no parsable information (e....
Definition: exceptions.h:18
Contains all classes and functions of the TagInfo library.
Definition: aaccodebook.h:10