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mp4.cpp
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mp4.cpp
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//==================================================================//
/*
Untrunc - mp4.cpp
Untrunc is GPL software; you can freely distribute,
redistribute, modify & use under the terms of the GNU General
Public License; either version 2 or its successor.
Untrunc is distributed under the GPL "AS IS", without
any warranty; without the implied warranty of merchantability
or fitness for either an expressed or implied particular purpose.
Please see the included GNU General Public License (GPL) for
your rights and further details; see the file COPYING. If you
cannot, write to the Free Software Foundation, 59 Temple Place
Suite 330, Boston, MA 02111-1307, USA. Or www.fsf.org
Copyright 2010 Federico Ponchio
*/
//==================================================================//
#include <cassert>
#include <vector>
#include <set>
#include <algorithm>
#include <functional>
#include <string>
#include <iostream>
#include <ios> // Pre-C++11: may not be included by <iostream>.
#include <iomanip>
#include <limits>
#ifndef __STDC_LIMIT_MACROS
# define __STDC_LIMIT_MACROS 1
#endif
#ifndef __STDC_CONSTANT_MACROS
# define __STDC_CONSTANT_MACROS 1
#endif
extern "C" {
#include <stdint.h>
#ifdef _WIN32
# include <io.h> // for: _isatty()
#else
# include <unistd.h> // for: isatty()
#endif
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libavutil/log.h"
} // extern "C"
#include "mp4.h"
#include "atom.h"
#include "file.h"
#include "log.h"
// Stdio file descriptors.
#ifndef STDIN_FILENO
# define STDIN_FILENO 0
# define STDOUT_FILENO 1
# define STDERR_FILENO 2
#endif
#include <algorithm>
using namespace std;
namespace {
const int MaxFrameLength = 20000000;
// Store start-up addresses of C++ stdio stream buffers as identifiers.
// These addresses differ per process and must be statically linked in.
// Assume that the stream buffers at these stored addresses
// are always connected to their underlaying stdio files.
static const streambuf* const StdioBufs[] = {
cin.rdbuf(), cout.rdbuf(), cerr.rdbuf(), clog.rdbuf()
};
// Store start-up terminal/TTY statuses of C++ stdio stream buffers.
// These statuses differ per process and must be statically linked in.
// Assume that the statuses don't change during the process life-time.
static const bool StdioTtys[sizeof(StdioBufs)/sizeof(StdioBufs[0])] = {
#ifdef _WIN32
_isatty(STDIN_FILENO), _isatty(STDOUT_FILENO), _isatty(STDERR_FILENO), _isatty(STDERR_FILENO)
#else
(bool)isatty(STDIN_FILENO), (bool)isatty(STDOUT_FILENO), (bool)isatty(STDERR_FILENO), (bool)isatty(STDERR_FILENO)
#endif
};
// Is a Terminal/Console/TTY connected to the C++ stream?
// Use on C++ stdio chararacter streams: cin, cout, cerr and clog.
bool isATerminal(const ios& strm) {
for(unsigned int i = 0; i < sizeof(StdioBufs)/sizeof(StdioBufs[0]); ++i) {
if(strm.rdbuf() == StdioBufs[i])
return StdioTtys[i];
}
return false;
}
// Configure FFmpeg/Libav logging for use in C++.
class AvLog {
int lvl;
#ifdef AV_LOG_PRINT_LEVEL
int flgs;
#endif
public:
#ifdef AV_LOG_PRINT_LEVEL
# define DEFAULT_AVLOG_FLAGS AV_LOG_PRINT_LEVEL
#else
# define DEFAULT_AVLOG_FLAGS 0
#endif
explicit AvLog()
: lvl(av_log_get_level())
#ifdef AV_LOG_PRINT_LEVEL
, flgs(av_log_get_flags())
#endif
{
av_log_set_flags(DEFAULT_AVLOG_FLAGS);
// cout.flush(); // Flush C++ standard streams.
//cerr.flush(); // Unbuffered -> nothing to flush.
// clog.flush();
}
explicit AvLog(int level, int flags = DEFAULT_AVLOG_FLAGS)
: lvl(av_log_get_level())
#ifdef AV_LOG_PRINT_LEVEL
, flgs(av_log_get_flags())
#endif
{
if(lvl < level)
av_log_set_level(level);
av_log_set_flags(flags);
cout.flush(); // Flush C++ standard streams.
//cerr.flush(); // Unbuffered -> nothing to flush.
clog.flush();
}
~AvLog() {
fflush(stdout); // Flush C stdio files.
fflush(stderr);
av_log_set_level(lvl);
#ifdef AV_LOG_PRINT_LEVEL
av_log_set_flags(flgs);
#endif
}
};
// Redirect C files.
// This does not effect C++ standard I/O streams (cin, cout, cerr, clog).
class FileRedirect {
FILE *&file_ref;
FILE * file_value;
public:
explicit FileRedirect(FILE *&file, FILE *to_file)
: file_ref(file)
, file_value(file)
{
file = to_file;
if(file_ref) fflush(file_ref);
}
~FileRedirect() {
if(file_ref) fflush(file_ref);
file_ref = file_value;
}
};
}; // namespace
// Mp4
Mp4::Mp4() : timescale(0), duration(0), root(NULL), context(NULL) { }
Mp4::~Mp4() {
close();
}
void Mp4::open(string filename) {
Log::debug << "Opening: " << filename << '\n';
close();
try { // Parse ok file.
File file;
if(!file.open(filename))
throw "Could not open file: " + filename;
root = new Atom;
do {
Atom *atom = new Atom;
atom->parse(file);
Log::debug << "Found atom: " << atom->name << '\n';
root->children.push_back(atom);
} while(!file.atEnd());
} catch(const string &error) {
Log::info << error << "\n";
Log::flush();
if(!root->atomByName("moov"))
throw string("Failed parsing working mp4. Maybe the broken and working files got inverted.");
}/* catch(...) {
throw string("Failed parsing working mp4. Maybe the broken and working files got inverted.");
}*/
// {
file_name = filename;
if(root->atomByName("ctts"))
Log::debug << "Found 'Composition Time To Sample' atom (ctts). Out of order samples possible.\n";
if(root->atomByName("sdtp"))
Log::debug << "Found 'Independent and Disposable Samples' atom (sdtp). I and P frames might need to recover that info.\n";
Atom *mvhd = root->atomByName("mvhd");
if(!mvhd)
throw string("Missing 'Movie Header' atom (mvhd)");
// ASSUME: mvhd atom version 0.
timescale = mvhd->readInt(12);
duration = mvhd->readInt(16);
{ // Setup AV library.
AvLog useAvLog();
// Register all formats and codecs.
av_register_all();
// Open video file.
#ifdef OLD_AVFORMAT_API
int error = av_open_input_file(&context, filename.c_str(), NULL, 0, NULL);
#else
int error = avformat_open_input(&context, filename.c_str(), NULL, NULL);
#endif
if(error != 0)
throw "Could not parse AV file: " + filename;
// Retrieve stream information.
#ifdef OLD_AVFORMAT_API
if(av_find_stream_info(context) < 0)
#else
if(avformat_find_stream_info(context, NULL) < 0)
#endif
throw string("Could not find stream info");
} // {
parseTracks();
}
void Mp4::close() {
Atom *rm_root = root;
root = NULL; // Invalidate Mp4 data.
timescale = 0;
duration = 0;
tracks.clear(); // Must clear tracks before closing context.
if(context) {
AvLog useAvLog(AV_LOG_ERROR);
#ifdef OLD_AVFORMAT_API
av_close_input_file(&context);
#else
avformat_close_input(&context);
#endif
context = NULL;
}
file_name.clear();
delete rm_root;
}
void Mp4::printMediaInfo() {
if(context) {
cout.flush();
clog.flush();
Log::info << "Media Info:\n"
<< " Default stream: " << av_find_default_stream_index(context) << '\n';
AvLog useAvLog(AV_LOG_INFO);
FileRedirect redirect(stderr, stdout);
av_dump_format(context, 0, file_name.c_str(), 0);
}
}
void Mp4::printAtoms() {
if(root) {
Log::info << "Atoms:\n";
root->print(0);
}
}
bool Mp4::makeStreamable(string filename, string output_filename) {
Log::info << "Make Streamable: " << filename << '\n';
Atom atom_root;
{ // Parse input file.
File file;
if(!file.open(filename))
throw "Could not open file: " + filename;
while(!file.atEnd()) {
Atom *atom = new Atom;
atom->parse(file);
Log::debug << "Found atom: " << atom->name << '\n';
atom_root.children.push_back(atom);
}
} // {
Atom *ftyp = atom_root.atomByName("ftyp");
Atom *moov = atom_root.atomByName("moov");
Atom *mdat = atom_root.atomByName("mdat");
if(!moov || !mdat) {
if(!moov)
Log::error << "Missing 'Container for all the Meta-data' atom (moov).\n";
if(!mdat)
Log::error << "Missing 'Media Data container' atom (mdat).\n";
return false;
}
if(mdat->start > moov->start) {
Log::info << "File is already streamable." << endl;
return true;
}
int64_t old_start = mdat->start + 8;
int64_t new_start = moov->length + 8;
if(ftyp)
new_start += ftyp->length;
int64_t diff = new_start - old_start;
Log::debug << "Old: " << old_start << " -> New: " << new_start << '\n';
#if 0 // MIGHT HAVE TO FIX THIS ONE TOO?
Atom *co64 = trak->atomByName("co64");
if(co64) {
trak->prune("co64");
Atom *stbl = trak->atomByName("stbl");
if(stbl) {
Atom *new_stco = new Atom;
memcpy(new_stco->name, "stco", min(sizeof("stco"), sizeof(new_stco->name)-1));
stbl->children.push_back(new_stco);
}
}
#endif
std::vector<Atom *> stcos = moov->atomsByName("stco");
for(unsigned int i = 0; i < stcos.size(); ++i) {
Atom *stco = stcos[i];
int32_t nchunks = stco->readInt(4); // 4 version, 4 number of entries, 4 entries.
for(int j = 0; j < nchunks; ++j) {
int64_t pos = int64_t(8) + 4*j;
int64_t offset = stco->readInt(pos) + diff;
Log::debug << "O: " << offset << '\n';
stco->writeInt(offset, pos);
}
}
{ // Save to output file.
Log::debug << "Saving to: " << output_filename << '\n';
File file;
if(!file.create(output_filename))
throw "Could not create file for writing: " + output_filename;
if(ftyp)
ftyp->write(file);
moov->write(file);
mdat->write(file);
} // {
Log::debug << endl;
return true;
}
bool Mp4::save(string output_filename) {
// We save all atoms except:
// ctts: composition offset (we use sample to time).
// cslg: because it is used only when ctts is present.
// stps: partial sync, same as sync.
//
// Movie is made by ftyp, moov, mdat (we need to know mdat begin, for absolute offsets).
// Assume offsets in stco are absolute and so to find the relative just subtrack mdat->start + 8.
Log::info << "Saving to: " << output_filename << '\n';
if(!root) {
Log::error << "No file opened.\n";
return false;
}
if(timescale == 0) {
timescale = 600; // Default movie time scale.
Log::info << "Using new movie time scale: " << timescale << ".\n";
}
duration = 0;
for(unsigned int i = 0; i < tracks.size(); ++i) {
Track &track = tracks[i];
Log::debug << "Track " << i << " (" << track.codec.name << "): duration: "
<< track.duration << " timescale: " << track.timescale << '\n';
if(track.timescale == 0 && track.duration != 0)
Log::info << "Track " << i << " (" << track.codec.name << ") has no time scale.\n";
track.writeToAtoms();
// Convert duration to movie timescale.
if(timescale == 0) continue; // Shouldn't happen.
// Use default movie time scale if no track time scale was found.
int track_timescale = (track.timescale != 0) ? track.timescale : 600;
//convert track duration (in track.timescale units) to movie timesscale units.
int track_duration = static_cast<int>((int64_t(track.duration) * timescale - 1 + track_timescale)
/ track_timescale);
if(duration < track_duration)
duration = track_duration;
Atom *tkhd = track.trak->atomByName("tkhd");
if(!tkhd) {
Log::debug << "Missing 'Track Header' atom (tkhd).\n";
continue;
}
if(tkhd->readInt(20) == track_duration) continue;
Log::debug << "Adjusting track duration to movie timescale: New duration: "
<< track_duration << " timescale: " << timescale << ".\n";
tkhd->writeInt(track_duration, 20); // In movie timescale, not track timescale.
}
Log::debug << "Movie duration: " << duration/(double)timescale << "s with timescale: " << timescale << '\n';
Atom *mvhd = root->atomByName("mvhd");
if(!mvhd)
throw string("Missing 'Movie Header' atom (mvhd)");
mvhd->writeInt(duration, 16);
Atom *ftyp = root->atomByName("ftyp");
Atom *moov = root->atomByName("moov");
Atom *mdat = root->atomByName("mdat");
if(!moov || !mdat) {
if(!moov)
Log::error << "Missing 'Container for all the Meta-data' atom (moov).\n";
if(!mdat)
Log::error << "Missing 'Media Data container' atom (mdat).\n";
return false;
}
moov->prune("ctts");
moov->prune("cslg");
moov->prune("stps");
root->updateLength();
//we need to add mdat header bytes
int64_t offset = moov->length + 8;
if(mdat->length64)
offset += 8;
if(ftyp)
offset += ftyp->length; // Not all .mov have an ftyp.
for(unsigned int t = 0; t < tracks.size(); ++t) {
Track &track = tracks[t];
for(unsigned int i = 0; i < track.offsets.size(); ++i)
track.offsets[i] += offset;
track.writeToAtoms(); // Need to save the offsets back to the atoms.
}
{ // Save to output file.
File file;
if(!file.create(output_filename))
throw "Could not create file for writing: " + output_filename;
if(ftyp)
ftyp->write(file);
moov->write(file);
mdat->write(file);
} // {
return true;
}
//used for variable sample time attempt to guess
class ChunkTime: public Track::Chunk {
public:
int sample;
int sample_time;
int track;
bool operator<(const ChunkTime &c) const { return offset < c.offset; }
};
void Mp4::analyze(int analyze_track, bool interactive) {
Log::info << "Analyze:\n";
if(!root) {
Log::error << "No file opened.\n";
return;
}
Atom *_mdat = root->atomByName("mdat");
if(!_mdat) {
Log::error << "Missing 'Media Data container' atom (mdat).\n";
return;
}
BufferedAtom *mdat = bufferedMdat(_mdat);
if(interactive) {
// For interactive analyzis, std::cin & std::cout must be connected to a terminal/tty.
if(!isATerminal(cin)) {
Log::debug << "Cannot analyze interactively as input doesn't come directly from a terminal.\n";
interactive = false;
}
if(interactive && !isATerminal(cout)) {
Log::debug << "Cannot analyze interactively as output doesn't go directly to a terminal.\n";
interactive = false;
}
if(interactive)
cin.clear(); // Reset state - clear transient errors of previous input operations.
#ifdef VERBOSE1
clog.flush();
#endif
}
//sample time analysis
vector<ChunkTime> chunktimes;
for(unsigned int trackId = 0; trackId < tracks.size(); ++trackId) {
if(analyze_track != -1 && trackId != analyze_track)
continue;
Log::info << "\n\nTrack " << trackId << endl;
Track &track = tracks[trackId];
if(track.hint_track) {
Log::info << "Hint track for track: " << track.hinted_id << "\n";
} else {
Log::info << "Track codec: " << track.codec.name << '\n';
}
Log::info << "Keyframes : " << track.keyframes.size() << "\n\n";
if(track.codec.pcm) {
Log::info << "PCM codec, skipping keyframes\n\n";
} else if(track.default_size) {
Log::info << "Default size packets, skipping keyframes\n\n";
} else {
for(unsigned int i = 0; i < track.keyframes.size(); ++i) {
int k = track.keyframes[i];
int64_t offset = track.offsets[k] - mdat->content_start;
uint32_t begin = mdat->readInt(offset);
uint32_t next = mdat->readInt(offset + 4);
Log::debug << setw(8) << k
<< " Size: " << setw(6) << track.getSize(k)
<< " offset " << setw(10) << track.offsets[k]
<< " begin: " << hex << setw(5) << begin << ' ' << setw(8) << next << dec
<< " time: " << (track.default_time ? track.default_time : track.times[i]) << '\n';
}
}
if(track.default_size) {
Log::info << "Constant size for samples: " << track.default_size << "\n";
} else {
Log::info << "Sizes for samples: " << "\n";
for(int i = 0; i < 10 && i < track.sample_sizes.size(); i++) {
Log::info << track.sample_sizes[i] << " ";
}
Log::info << "\n";
}
if(track.default_time) {
Log::info << "Constant time for packet: " << track.default_time << endl;
}
if(track.default_size) {
if(!track.codec.pcm) {
Log::info << "Not a PCM codec, default size though.. we have hope.\n";
}
int i = 0;
for(Track::Chunk &chunk: track.chunks) {
int64_t offset = chunk.offset - mdat->content_start;
int64_t maxlength64 = mdat->contentSize() - offset;
if(maxlength64 > MaxFrameLength)
maxlength64 = MaxFrameLength;
int maxlength = static_cast<int>(maxlength64);
int32_t begin = mdat->readInt(offset);
int32_t next = mdat->readInt(offset + 4);
int32_t end = mdat->readInt(offset + track.getSize(i) - 4);
Log::info << " Size: " << setw(6) << chunk.size
<< " offset " << setw(10) << chunk.offset
<< " begin: " << hex << setw(8) << begin << ' ' << setw(8) << next
<< " end: " << setw(8) << end << dec
<< " time: " << (track.default_time ? track.default_time : track.times[i]) << '\n';
i++;
}
}
int sample = 0;
for(unsigned int i = 0; i < track.chunks.size(); ++i) {
Track::Chunk &chunk = track.chunks[i];
ChunkTime chunktime;
chunktime.offset = chunk.offset;
chunktime.nsamples = chunk.nsamples;
chunktime.size = chunk.size;
chunktime.track = trackId;
chunktime.sample_time = 0;
int64_t offset = chunk.offset - mdat->content_start;
for(int k = 0; k < chunk.nsamples; k++) {
int64_t size = track.getSize(chunk.first_sample + k);
if(track.codec.pcm)
size = chunk.size;
int64_t extendedsize = std::min(mdat->contentSize() - offset, size + 200000);
unsigned char *start = mdat->getFragment(offset, extendedsize); //&(mdat->content[offset]);
int32_t begin = mdat->readInt(offset);
int32_t next = mdat->readInt(offset + 4);
Log::info << " Size: " << setw(6) << size
<< " offset " << setw(10) << offset + mdat->content_start
<< " begin: " << hex << setw(8) << begin << ' ' << setw(8) << next << dec << '\n';
chunktime.sample_time += track.default_time ? track.default_time : track.times[sample];
Match match = track.codec.match(start, extendedsize);
MatchGroup matches = this->match(offset, mdat);
Match &best = matches.back();
if(best.id != trackId) {
Log::error << "Wrong track matches with higher score";
MatchGroup rematches = this->match(offset, mdat);
}
if(track.codec.pcm)
break;
sample++;
offset += size;
if(match.length == size)
continue;
if(match.length == 0) {
Log::error << "- Match failed!\n";
} else if(match.length < 0 || match.length > MaxFrameLength) {
Log::error << "- Invalid length!\n";
} else {
Log::error << "- Length mismatch: got " << match.length << " expected: " << size << "\n";
}
if(interactive) {
Log::info << " <Press [Enter] for next match>\r";
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
}
chunktimes.push_back(chunktime);
}
}
cout << "Chunks " << tracks[1].chunks.size() << " times: " << tracks[1].times.size() << endl;
std::sort(chunktimes.begin(), chunktimes.end());
vector<float> times(tracks.size(), 0);
int count = 0;
for(ChunkTime &c: chunktimes) {
times[c.track] += c.sample_time / (float)tracks[c.track].timescale;
cout << "Track: " << c.track << " time: " << c.sample_time << " nsamples: " << c.nsamples << " tot: " << times[c.track] << endl;
if(count++ > 200)
break; }
}
void Mp4::simulate(Mp4::MdatStrategy strategy, int64_t begin) {
//TODO remove duplicated code with analyze.
Log::info << "Simulate:\n";
if(!root) {
Log::error << "No file opened.\n";
return;
}
Atom *original_mdat = root->atomByName("mdat");
if(!original_mdat) {
Log::error << "Missing 'Media Data container' atom (mdat).\n";
return;
}
BufferedAtom *mdat = findMdat(file_name, strategy);
if(!mdat) {
Log::error << "MDAT not found.\n";
return;
}
//sort packets by start, length, track id
std::vector<Match> packets;
std::string codecs[tracks.size()];
for(unsigned int t = 0; t < tracks.size(); ++t) {
Track &track = tracks[t];
codecs[t] = track.codec.name;
//if pcm -> offsets should be chunks!
if(track.default_size) {
Log::debug << "Track " << t << " packets: " << track.chunks.size() << endl;
for(unsigned int i = 0;i < track.chunks.size(); i++) {
Track::Chunk &chunk = track.chunks[i];
Match match;
match.id = t;
match.offset = chunk.offset;
match.length = chunk.size;
match.duration = track.default_time? track.default_time : track.times[i];
packets.push_back(match);
}
} else {
Log::debug << "Track " << t << " packets: " << track.offsets.size() << endl;
for(unsigned int i = 0; i < track.chunks.size(); ++i) {
Track::Chunk &chunk = track.chunks[i];
uint64_t offset = chunk.offset;
for(int k = 0; k < chunk.nsamples; k++) {
Match match;
match.id = t;
match.offset = offset;
match.length = track.getSize(chunk.first_sample + k);
match.duration = track.getTimes(k);
packets.push_back(match);
offset += match.length;
}
}
/*
for(unsigned int i = 0; i < track.offsets.size(); ++i) {
Match match;
match.id = t;
match.offset = track.offsets[i];
match.length = track.chunk_sizes[i];
match.duration = track.default_time? track.default_time : track.times[i];
packets.push_back(match);
}*/
}
}
std::sort(packets.begin(), packets.end(), [](const Match &m1, const Match &m2) { return m1.offset < m2.offset; });
if(packets[0].offset != original_mdat->content_start) {
Log::error << "First packet does not start with mdat, finding the start of the packets might be problematic" << endl;
}
//ensure mdat is correctly found.
if(original_mdat->content_start != mdat->file_begin) {
Log::error << "Wrong start of mdat: " << mdat->file_begin << " should be " << original_mdat->content_start << "\n";
mdat->file_begin = mdat->content_start = packets[0].offset;
}
int64_t offset = 0; //mdat->file_begin;
for(Match &m: packets) {
if(m.offset != mdat->file_begin + offset) {
Log::error << "Some empty space to be skipped! Real start = " << m.offset << " mdat start guessed at: " << offset + mdat->file_begin << "\n";
break;
}
unsigned char *start = mdat->getFragment(offset, 8);
unsigned int begin = readBE<int>(start);
unsigned int next = readBE<int>(start + 4);
Log::debug << "\n" << codecs[m.id] << " (" << m.id << ") offset: " << setw(10) << (m.offset) << " Length: " << m.length
<< " begin: " << hex << setw(8) << begin << ' ' << setw(8) << next << dec << "\n";
MatchGroup matches = match(offset, mdat);
Match &best = matches.back();
for(Match m: matches) {
Log::debug << "Match for: " << m.id << " (" << codecs[m.id] << ") chances: " << m.chances << " length: " << m.length << "\n";
}
if(best.chances == 0.0f) {
//we could not detect best, in reconstruction we need to backtrack
Log::error << "Could not match packet for track " << m.id << "\n";
Log::flush();
Log::info << " <Press [Enter] for next match>\r";
cin.ignore(numeric_limits<streamsize>::max(), '\n');
// break;
}
if(m.id != best.id) {
Log::error << "Mismatch! Packet track should be on track: " << m.id << " (" << codecs[m.id] << ") it is: " << best.id << " (" << codecs[best.id] << ")\n";
Log::flush();
Log::info << " <Press [Enter] for next match>\r";
cin.ignore(numeric_limits<streamsize>::max(), '\n');
// break;
}
if(m.length != best.length) {
Log::error << "Packet length is wrong." << endl;
Log::flush();
Log::info << " <Press [Enter] for next match>\r";
cin.ignore(numeric_limits<streamsize>::max(), '\n');
// break;
}
offset += m.length;
}
}
MatchGroup Mp4::match(int64_t offset, BufferedAtom *mdat) {
MatchGroup group;
group.offset = offset;
int64_t maxlength64 = mdat->contentSize() - offset;
if(maxlength64 > MaxFrameLength)
maxlength64 = MaxFrameLength;
unsigned char *start = mdat->getFragment(offset, maxlength64);
int maxlength = static_cast<int>(maxlength64);
for(unsigned int i = 0; i < tracks.size(); ++i) {
Track &track = tracks[i];
Match m = track.codec.match(start, maxlength);
m.id = i;
m.offset = group.offset;
group.push_back(m);
}
sort(group.begin(), group.end());//, [](const Match &m1, const Match &m2) { return m1.chances > m2.chances; });
return group;
}
void Mp4::writeTracksToAtoms() {
for(unsigned int i = 0; i < tracks.size(); ++i)
tracks[i].writeToAtoms();
}
bool Mp4::parseTracks() {
assert(root != NULL);
Atom *_mdat = root->atomByName("mdat");
if(!_mdat) {
Log::error << "Missing 'Media Data container' atom (mdat).\n";
return false;
}
BufferedAtom *mdat = bufferedMdat(_mdat);
vector<Atom *> traks = root->atomsByName("trak");
for(unsigned int i = 0; i < traks.size(); ++i) {
Track track;
track.codec.context = context->streams[i]->codec;
track.parse(traks[i]);
track.codec.stats.init(track, mdat);
tracks.push_back(track);
}
return true;
}
BufferedAtom *Mp4::bufferedMdat(Atom *mdat) {
BufferedAtom *_mdat = new BufferedAtom(file_name);
_mdat->start = mdat->start;
memcpy(_mdat->name, "mdat", 5);
_mdat->content_start = mdat->start;
_mdat->file_begin = mdat->start;
_mdat->file_end = _mdat->file.length();
return _mdat;
}
BufferedAtom *Mp4::findMdat(std::string filename, Mp4::MdatStrategy strategy) {
BufferedAtom *mdat = new BufferedAtom(filename);
int64_t start = findMdat(mdat, strategy);
if(start < 0) {
delete mdat;
return nullptr;
}
mdat->start = 0; //will be overwritten in repair.
memcpy(mdat->name, "mdat", 5);
mdat->content_start = start;
mdat->file_begin = start;
mdat->file_end = mdat->file.length();
return mdat;
}
/* strategy:
*
* 1) Look for mdat. It's almost always a good start, but sometime, the actual packets can start from 8 to 200000k and more after.
* 1.a) if non start guessable packets with fixed lenght are present we are blindly looking for them
* 2.b) if we have guessable start make a map of possible starts and check with what we have found, in that case we need to lookup find mdat start with a different approach.
* 2) if method 1 fails, we need to look for start guessable packets.
*
* Note: avc1 has size then start and for keyframes they are pretty guessable.
*/
int64_t Mp4::contentStart() {
vector<int64_t> offsets;
for(Track &track: tracks) {
for(Track::Chunk &chunk: track.chunks) {
offsets.push_back(chunk.offset);
break;
}
}
sort(offsets.begin(), offsets.end());
return offsets[0];
}
int64_t Mp4::findMdat(BufferedAtom *mdat, Mp4::MdatStrategy strategy) {
if(strategy == SAME)
return contentStart();
//look for mdat
int64_t mdat_offset = -1;
char m[4];
m[3] = 0;
//look for mdat in the first 20 MB
int64_t length = std::min(int64_t(20000000), mdat->file_end - mdat->file_begin);
uint8_t *data = mdat->getFragment(0, length);
if(strategy == FIRST || strategy == LAST) {
for(uint64_t i = 4; i < length-4; i++) {
uint32_t c = readBE<uint32_t>(data + i);
if(c != 0x6D646174) //mdat
continue;
mdat_offset = i+4;
//check if its 64bit mdat
uint32_t size = readBE<uint32_t>(data + i -4);
if(size == 1)
mdat_offset += 8;
//sometimes the length is not specified and still the first packet starts at +8 (see in repair)
if(strategy == FIRST)
break;
}
} else if(strategy == SEARCH) {
//TODO if we have some unique beginnigs, try to spot the first one.
for(uint64_t i = 4; i < length-4; i++) {
uint32_t c = readBE<uint32_t>(data + i);
if(c == 0) continue;
for(Track &track: tracks) {
//might want to look for video keyframes and actually skip the size of the frame (which is useless).
if(track.codec.stats.beginnings32.count(c)) {
mdat_offset = i;
break;
}
}
if(mdat_offset != -1)
break;
}
}
mdat->flush();
if(mdat_offset != -1) {
mdat->start = mdat_offset - 8;
mdat->content_start = mdat_offset;
}
Log::info << "Mdat not found!" << endl;
return mdat_offset;
}
//skip vast tract of zeros (up to the last one.
//multiple of 1024. If it's all zeros skip.
//if it's less than 8 bytes dont (might be alac?)
//otherwise we need to search for the actual begin using matches.
int zeroskip(BufferedAtom *mdat, unsigned char *start, int64_t maxlength) {
int64_t block_size = std::min(int64_t(1<<10), maxlength);
//skip 4 bytes at a time.
int k = 0;
for(;k < block_size - 4; k+= 4) {
int value = readBE<int>(start + k);
if(value != 0)
break;
}
//don't skip very short zero sequences
if(k < 16)
return 0;
//play conservative of non aligned zero blocks
if(k < block_size)
k -= 4;
//zero bytes block aligned.
Log::debug << "Skipping zero bytes: " << k << "\n";
return k;
}
int Mp4::searchNext(BufferedAtom *mdat, int64_t offset, int maxskip) {
int64_t maxlength64 = mdat->contentSize() - offset;
if(maxlength64 > MaxFrameLength)
maxlength64 = MaxFrameLength;
unsigned char *start = mdat->getFragment(offset, maxlength64);
int maxlength = static_cast<int>(maxlength64);
Match best;
best.chances = 0;