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Matroska reader: only analyze last 5 MB of a file if no seek head is found

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This commit is contained in:
Moritz Bunkus 2015-11-29 11:03:51 +01:00
parent 92f054dc79
commit dfee7a2226
4 changed files with 30 additions and 7 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2015-11-29 Moritz Bunkus <moritz@bunkus.org>
* mkvmerge: bug fix: the change to do a deeper file analysis if no
seek head was found was causing huge increases in file type
detection time as popular tools like x264 don't write seek
heads. The way elements at the end are searched has been changed
to only scan the last 5 MB of the file instead of iterating over
every level 1 element from the beginning of the file.
2015-11-28 Moritz Bunkus <moritz@bunkus.org>
* Released v8.6.0.

14
src/common/kax_analyzer.cpp
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@ -216,6 +216,12 @@ kax_analyzer_c::set_throw_on_error(bool throw_on_error) {
return *this;
}
kax_analyzer_c &
kax_analyzer_c::set_parser_start_position(uint64_t position) {
m_parser_start_position.reset(position);
return *this;
}
bool
kax_analyzer_c::process() {
try {
@ -278,6 +284,14 @@ kax_analyzer_c::process_internal() {
auto segment_end = m_segment->IsFiniteSize() ? m_segment->GetElementPosition() + m_segment->HeadSize() + m_segment->GetSize() : m_file->get_size();
EbmlElement *l1 = nullptr;
// In certain situations the caller doesn't way to have to pay the
// price for full analysis. Then it can configure the parser to
// start parsing at a certain offset. EbmlStream::FindNextElement()
// should take care of re-syncing to a known level 1 element. But
// take care not to start before the segment's data start position.
if (m_parser_start_position)
m_file->setFilePointer(std::max<uint64_t>(*m_parser_start_position, m_segment->GetElementPosition() + m_segment->HeadSize()));
// We've got our segment, so let's find all level 1 elements.
while (m_file->getFilePointer() < segment_end) {
if (!l1)

2
src/common/kax_analyzer.h
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@ -102,6 +102,7 @@ private:
parse_mode_e m_parse_mode{parse_mode_full};
open_mode m_open_mode{MODE_WRITE};
bool m_throw_on_error{};
boost::optional<uint64_t> m_parser_start_position;
public: // Static functions
static bool probe(std::string file_name);
@ -130,6 +131,7 @@ public:
virtual kax_analyzer_c &set_parse_mode(parse_mode_e parse_mode);
virtual kax_analyzer_c &set_open_mode(open_mode mode);
virtual kax_analyzer_c &set_throw_on_error(bool throw_on_error);
virtual kax_analyzer_c &set_parser_start_position(uint64_t position);
virtual bool process();

12
src/input/r_matroska.cpp
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@ -1205,15 +1205,13 @@ kax_reader_c::read_headers() {
void
kax_reader_c::find_level1_elements_via_analyzer() {
if (!debugging_c::requested("kax_reader_deep_scan"))
return;
try {
auto analyzer = std::make_shared<kax_analyzer_c>(m_in.get());
auto ok = analyzer
->set_parse_mode(kax_analyzer_c::parse_mode_fast)
auto start_pos = m_in->get_size() - std::min<int64_t>(m_in->get_size(), 5 * 1024 * 1024);
auto analyzer = std::make_shared<kax_analyzer_c>(m_in.get());
auto ok = analyzer
->set_parse_mode(kax_analyzer_c::parse_mode_full)
.set_open_mode(MODE_READ)
.set_throw_on_error(true)
.set_parser_start_position(start_pos)
.process();
if (!ok)