289 lines
9.3 KiB
C++
289 lines
9.3 KiB
C++
#include "./mp4atom.h"
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#include "./mp4container.h"
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#include "./mp4ids.h"
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#include "./mp4tag.h"
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#include "./mp4track.h"
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#include "../exceptions.h"
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#include "../mediafileinfo.h"
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#include <c++utilities/conversion/stringbuilder.h>
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#include <c++utilities/io/binaryreader.h>
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#include <c++utilities/io/binarywriter.h>
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#include <sstream>
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using namespace std;
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using namespace IoUtilities;
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using namespace ConversionUtilities;
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namespace TagParser {
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/*!
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* \class TagParser::Mp4Atom
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* \brief The Mp4Atom class helps to parse MP4 files.
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*/
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/*!
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* \brief Constructs a new top level atom with the specified \a container at the specified \a startOffset.
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*/
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Mp4Atom::Mp4Atom(GenericFileElement::ContainerType &container, uint64 startOffset)
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: GenericFileElement<Mp4Atom>(container, startOffset)
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{
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}
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/*!
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* \brief Constructs a new top level atom with the specified \a container at the specified \a startOffset.
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*/
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Mp4Atom::Mp4Atom(GenericFileElement::ContainerType &container, uint64 startOffset, uint64 maxSize)
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: GenericFileElement<Mp4Atom>(container, startOffset, maxSize)
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{
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}
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/*!
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* \brief Constructs a new sub level atom with the specified \a parent at the specified \a startOffset.
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*/
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Mp4Atom::Mp4Atom(Mp4Atom &parent, uint64 startOffset)
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: GenericFileElement<Mp4Atom>(parent, startOffset)
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{
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}
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/*!
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* \brief Returns the parsing context.
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*/
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string Mp4Atom::parsingContext() const
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{
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return "parsing " % idToString() % " atom at " + startOffset();
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}
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/*!
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* \brief Parses the MP4 atom.
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*/
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void Mp4Atom::internalParse(Diagnostics &diag)
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{
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static const string context("parsing MP4 atom");
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if (maxTotalSize() < minimumElementSize()) {
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diag.emplace_back(DiagLevel::Critical,
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argsToString("Atom is smaller than 8 byte and hence invalid. The remaining size within the parent atom is ", maxTotalSize(), '.'),
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context);
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throw TruncatedDataException();
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}
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stream().seekg(static_cast<streamoff>(startOffset()));
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m_dataSize = reader().readUInt32BE();
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if (m_dataSize == 0) {
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// atom size extends to rest of the file/enclosing container
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m_dataSize = maxTotalSize();
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}
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if (!m_dataSize) {
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diag.emplace_back(DiagLevel::Critical, "No data found (only null bytes).", context);
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throw NoDataFoundException();
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}
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if (m_dataSize < 8 && m_dataSize != 1) {
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diag.emplace_back(DiagLevel::Critical, "Atom is smaller than 8 byte and hence invalid.", context);
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throw TruncatedDataException();
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}
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m_id = reader().readUInt32BE();
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m_idLength = 4;
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if (m_dataSize == 1) { // atom denotes 64-bit size
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m_dataSize = reader().readUInt64BE();
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m_sizeLength = 12; // 4 bytes indicate long size denotation + 8 bytes for actual size denotation
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if (dataSize() < 16 && m_dataSize != 1) {
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diag.emplace_back(DiagLevel::Critical, "Atom denoting 64-bit size is smaller than 16 byte and hence invalid.", parsingContext());
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throw TruncatedDataException();
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}
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} else {
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m_sizeLength = 4;
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}
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if (maxTotalSize() < m_dataSize) { // currently m_dataSize holds data size plus header size!
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diag.emplace_back(DiagLevel::Warning, "The atom seems to be truncated; unable to parse siblings of that ", parsingContext());
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m_dataSize = maxTotalSize(); // using max size instead
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}
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// currently m_dataSize holds data size plus header size!
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m_dataSize -= headerSize();
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Mp4Atom *child = nullptr;
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if (uint64 firstChildOffset = this->firstChildOffset()) {
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if (firstChildOffset + minimumElementSize() <= totalSize()) {
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child = new Mp4Atom(static_cast<Mp4Atom &>(*this), startOffset() + firstChildOffset);
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}
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}
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m_firstChild.reset(child);
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Mp4Atom *sibling = nullptr;
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if (totalSize() < maxTotalSize()) {
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if (parent()) {
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sibling = new Mp4Atom(*(parent()), startOffset() + totalSize());
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} else {
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sibling = new Mp4Atom(container(), startOffset() + totalSize(), maxTotalSize() - totalSize());
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}
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}
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m_nextSibling.reset(sibling);
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}
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/*!
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* \brief This function helps to write the atom size after writing an atom to a stream.
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* \param stream Specifies the stream.
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* \param startOffset Specifies the start offset of the atom.
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* \remarks The caller must ensure that no seek before \a startOffset happended.
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* \throw The caller has to be sure, that the number of written bytes does not exceed
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* maximum of an 32-bit unsigned integer. Otherwise the function will throw
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* Failure and Mp4Atom::seekBackAndWriteAtomSize64 should be used instead.
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*
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* This function seeks back to the start offset and writes the difference between the
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* previous offset and the start offset as 32-bit unsigned integer to the \a stream.
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* Then it seeks back to the previous offset.
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*/
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void Mp4Atom::seekBackAndWriteAtomSize(std::ostream &stream, const ostream::pos_type &startOffset, Diagnostics &diag)
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{
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ostream::pos_type currentOffset = stream.tellp();
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const auto atomSize(currentOffset - startOffset);
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if (atomSize > numeric_limits<uint32>::max()) {
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diag.emplace_back(DiagLevel::Fatal, argsToString(atomSize, " exceeds maximum."), "write 32-bit atom size");
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throw Failure();
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}
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stream.seekp(startOffset);
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BinaryWriter writer(&stream);
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writer.writeUInt32BE(static_cast<uint32>(atomSize));
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stream.seekp(currentOffset);
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}
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/*!
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* \brief This function helps to write the atom size after writing an atom to a stream.
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* \param stream Specifies the stream.
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* \param startOffset Specifies the start offset of the atom.
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* \remarks The caller must ensure that no seek before \a startOffset happended.
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*
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* This function seeks back to the start offset and writes the difference between the
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* previous offset and the start offset as 64-bit unsigned integer to the \a stream.
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* Then it seeks back to the previous offset.
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*/
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void Mp4Atom::seekBackAndWriteAtomSize64(std::ostream &stream, const ostream::pos_type &startOffset)
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{
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ostream::pos_type currentOffset = stream.tellp();
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stream.seekp(startOffset);
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BinaryWriter writer(&stream);
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writer.writeUInt32BE(1);
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stream.seekp(4, ios_base::cur);
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writer.writeUInt64BE(static_cast<uint64>(currentOffset - startOffset));
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stream.seekp(currentOffset);
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}
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/*!
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* \brief Writes an MP4 atom header to the specified \a stream.
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*/
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void Mp4Atom::makeHeader(uint64 size, uint32 id, BinaryWriter &writer)
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{
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if (size < numeric_limits<uint32>::max()) {
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writer.writeUInt32BE(static_cast<uint32>(size));
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writer.writeUInt32BE(id);
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} else {
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writer.writeUInt32BE(1);
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writer.writeUInt32BE(id);
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writer.writeUInt64BE(size);
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}
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}
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/*!
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* \brief Returns an indication whether the atom is a parent element.
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*
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* \remarks This information is not read from the atom header. Some
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* atoms are simply known to be parents whereas all other
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* are considered as non-parents.
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*/
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bool Mp4Atom::isParent() const
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{
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using namespace Mp4AtomIds;
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// some atom ids are known to be parents
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switch (id()) {
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case Movie:
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case Track:
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case Media:
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case MediaInformation:
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case DataInformation:
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case SampleTable:
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case UserData:
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case Meta:
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case ItunesList:
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case MovieFragment:
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case TrackFragment:
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case MovieExtends:
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case DataReference:
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case Mp4AtomIds::AvcConfiguration:
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case FourccIds::Mpeg4Audio:
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case FourccIds::AmrNarrowband:
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case FourccIds::Amr:
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case FourccIds::Drms:
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case FourccIds::Alac:
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case FourccIds::WindowsMediaAudio:
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case FourccIds::Ac3:
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case FourccIds::EAc3:
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case FourccIds::DolbyMpl:
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case FourccIds::Dts:
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case FourccIds::DtsH:
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case FourccIds::DtsE:
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return true;
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default:
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if (parent()) {
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// some atom ids are known to contain parents
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switch (parent()->id()) {
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case ItunesList:
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return true;
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default:;
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}
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}
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}
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return false;
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}
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/*!
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* \brief Returns an indication whether the atom is a padding element.
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*
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* \remarks This information is not read from the atom header. Atoms with
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* the IDs "free" and "skip" are considered as padding.
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*/
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bool Mp4Atom::isPadding() const
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{
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using namespace Mp4AtomIds;
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switch (id()) {
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case Free:
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case Skip:
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return true;
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default:
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return false;
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}
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}
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/*!
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* \brief Returns the offset of the first child (relative to the start offset of this atom).
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*
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* \remarks This information is not read from the atom header. The offsets are known
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* for specific atoms.
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* \remarks This method returns zero for non-parent atoms which have no childs.
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* \remarks Childs with variable offset such as the "esds"-atom must be denoted!
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*/
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uint64 Mp4Atom::firstChildOffset() const
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{
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using namespace Mp4AtomIds;
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using namespace FourccIds;
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if (isParent()) {
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switch (id()) {
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case Meta:
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if (parent() && parent()->id() == Mp4AtomIds::UserData) {
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return headerSize() + 0x4u;
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}
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return headerSize();
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case DataReference:
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return headerSize() + 0x8u;
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default:
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return headerSize();
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}
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} else {
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switch (id()) {
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case SampleDescription:
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return headerSize() + 0x08u;
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default:
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return 0x00u;
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}
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}
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}
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} // namespace TagParser
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