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Fix messing track header of MP4 files (tkhd atom)

This commit is contained in:
Martchus 2017-09-14 01:37:15 +02:00
parent d4a406ba57
commit ba8c9204a9
2 changed files with 139 additions and 16 deletions
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153
mp4/mp4track.cpp
View File

@ -28,6 +28,44 @@ using namespace ChronoUtilities;
namespace Media {
/*!
* \brief The TrackHeaderInfo struct holds information about the present track header (tkhd atom) and
* information for making a new track header based on it.
* \sa TrackHeaderInfo Mp4Track::verifyPresentTrackHeader() for obtaining an instance.
* \remarks The struct is only used internally by the Mp4Track class.
*/
struct TrackHeaderInfo
{
friend class Mp4Track;
private:
TrackHeaderInfo();
/// \brief Specifies the size which is required for <i>making a new</i> track header based one the existing one.
uint64 requiredSize;
/// \brief Specifies whether there actually a track header exists and whether it can be used as basis for a new one.
bool canUseExisting;
/// \brief Specifies whether the existing track header is truncated.
bool truncated;
/// \brief Specifies the version of the existing track header.
byte version;
/// \brief Specifies whether the version of the existing track header is unknown (and assumed to be 1).
bool versionUnknown;
/// \brief Specifies the additional data offset of the existing header. Unspecified if canUseExisting is false.
byte additionalDataOffset;
/// \brief Specifies whether the buffered header data should be discarded when making a new track header.
bool discardBuffer;
};
inline TrackHeaderInfo::TrackHeaderInfo() :
requiredSize(100),
canUseExisting(false),
truncated(false),
version(0),
versionUnknown(false),
discardBuffer(false)
{}
/// \brief Dates within MP4 tracks are expressed as the number of seconds since this date.
const DateTime startDate = DateTime::fromDate(1904, 1, 1);
@ -358,6 +396,62 @@ void Mp4Track::addChunkSizeEntries(std::vector<uint64> &chunkSizeTable, size_t c
}
}
/*!
* \brief Verifies the present track header (tkhd atom) and returns relevant information for making a new track header
* based on it.
*/
TrackHeaderInfo Mp4Track::verifyPresentTrackHeader() const
{
TrackHeaderInfo info;
// return the default TrackHeaderInfo in case there is no track header prsent
if(!m_tkhdAtom) {
return info;
}
// ensure the tkhd atom is buffered but mark the buffer to be discarded again if it has not been present
info.discardBuffer = m_tkhdAtom->buffer() == nullptr;
if(info.discardBuffer) {
m_tkhdAtom->makeBuffer();
}
// check the version of the existing tkhd atom to determine where additional data starts
switch(info.version = static_cast<byte>(m_tkhdAtom->buffer()[m_tkhdAtom->headerSize()])) {
case 0:
info.additionalDataOffset = 32;
break;
case 1:
info.additionalDataOffset = 44;
break;
default:
info.additionalDataOffset = 44;
info.versionUnknown = true;
}
// check whether the existing tkhd atom is not truncated
if(info.additionalDataOffset + 48 <= m_tkhdAtom->dataSize()) {
info.canUseExisting = true;
} else {
info.truncated = true;
info.canUseExisting = info.additionalDataOffset < m_tkhdAtom->dataSize();
if(!info.canUseExisting && info.discardBuffer) {
m_tkhdAtom->discardBuffer();
}
}
// determine required size
info.requiredSize = m_tkhdAtom->dataSize() + 8;
if(info.version == 0) {
// add 12 byte to size if the existing version is 0 because we always write version 1 which takes 12 byte more space
info.requiredSize += 12;
}
if(info.requiredSize > numeric_limits<uint32>::max()) {
// add 8 byte to the size because it must be denoted using a 64-bit integer
info.requiredSize += 8;
}
return info;
}
/*!
* \brief Reads the sample to chunk table.
* \returns Returns a vector with the table entries wrapped using the tuple container. The first value
@ -973,8 +1067,10 @@ void Mp4Track::bufferTrackAtoms()
uint64 Mp4Track::requiredSize() const
{
// add size of
// ... trak header and tkhd total size
uint64 size = 8 + 100;
// ... trak header
uint64 size = 8;
// ... tkhd atom (TODO: buffer TrackHeaderInfo in v7)
size += verifyPresentTrackHeader().requiredSize;
// ... tref atom (if one exists)
if(Mp4Atom *trefAtom = m_trakAtom->childById(Mp4AtomIds::TrackReference)) {
size += trefAtom->totalSize();
@ -1050,9 +1146,31 @@ void Mp4Track::makeTrack()
*/
void Mp4Track::makeTrackHeader()
{
writer().writeUInt32BE(100); // size
writer().writeUInt32BE(Mp4AtomIds::TrackHeader);
writer().writeByte(1); // version
// verify the existing track header to make the new one based on it (if possible)
const TrackHeaderInfo info(verifyPresentTrackHeader());
// add notifications in case the present track header could not be parsed
if(info.versionUnknown) {
addNotification(NotificationType::Critical, argsToString("The version of the present \"tkhd\"-atom (", info.version, ") is unknown. Assuming version 1."),
argsToString("making \"tkhd\"-atom of track ", m_id));
}
if(info.truncated) {
addNotification(NotificationType::Critical, argsToString("The present \"tkhd\"-atom is truncated."),
argsToString("making \"tkhd\"-atom of track ", m_id));
}
// make size and element ID
if(info.requiredSize > numeric_limits<uint32>::max()) {
writer().writeUInt32BE(1);
writer().writeUInt32BE(Mp4AtomIds::TrackHeader);
writer().writeUInt64BE(info.requiredSize);
} else {
writer().writeUInt32BE(static_cast<uint32>(info.requiredSize));
writer().writeUInt32BE(Mp4AtomIds::TrackHeader);
}
// make version and flags
writer().writeByte(1);
uint32 flags = 0;
if(m_enabled) {
flags |= 0x000001;
@ -1064,28 +1182,31 @@ void Mp4Track::makeTrackHeader()
flags |= 0x000004;
}
writer().writeUInt24BE(flags);
// make creation and modification time
writer().writeUInt64BE(static_cast<uint64>((m_creationTime - startDate).totalSeconds()));
writer().writeUInt64BE(static_cast<uint64>((m_modificationTime - startDate).totalSeconds()));
writer().writeUInt32BE(m_id);
// make track ID and duration
writer().writeUInt32BE(static_cast<uint32>(m_id));
writer().writeUInt32BE(0); // reserved
writer().writeUInt64BE(static_cast<uint64>(m_duration.totalSeconds() * m_timeScale));
writer().writeUInt32BE(0); // reserved
writer().writeUInt32BE(0); // reserved
if(m_tkhdAtom) {
// use existing values
if(m_tkhdAtom->buffer()) {
m_ostream->write(m_tkhdAtom->buffer().get() + 52, 48);
} else {
char buffer[48];
m_istream->seekg(m_tkhdAtom->startOffset() + 52);
m_istream->read(buffer, sizeof(buffer));
m_ostream->write(buffer, sizeof(buffer));
// make further values, either from existing tkhd atom or just some defaults
if(info.canUseExisting) {
// write all bytes after the previously determined additionalDataOffset
m_ostream->write(m_tkhdAtom->buffer().get() + m_tkhdAtom->headerSize() + info.additionalDataOffset, m_tkhdAtom->dataSize() - info.additionalDataOffset);
// discard the buffer again if it wasn't present before
if(info.discardBuffer) {
m_tkhdAtom->discardBuffer();
}
} else {
// write default values
writer().writeInt16BE(0); // layer
writer().writeInt16BE(0); // alternate group
writer().writeFixed8BE(1.0); // volume
writer().writeFixed8BE(1.0); // volume (fixed 8.8 - 2 byte)
writer().writeUInt16BE(0); // reserved
for(const int32 value : {0x00010000,0,0,0,0x00010000,0,0,0,0x40000000}) { // unity matrix
writer().writeInt32BE(value);

2
mp4/mp4track.h
View File

@ -12,6 +12,7 @@ namespace Media
class Mp4Atom;
class Mpeg4Descriptor;
struct AvcConfiguration;
struct TrackHeaderInfo;
class TAG_PARSER_EXPORT Mpeg4AudioSpecificConfig
{
@ -166,6 +167,7 @@ private:
// private helper methods
uint64 accumulateSampleSizes(size_t &sampleIndex, size_t count);
void addChunkSizeEntries(std::vector<uint64> &chunkSizeTable, size_t count, size_t &sampleIndex, uint32 sampleCount);
TrackHeaderInfo verifyPresentTrackHeader() const;
Mp4Atom *m_trakAtom;
Mp4Atom *m_tkhdAtom;