void
MP4::AudioProperties::read(File *file, Atoms *atoms)
{
MP4::Atom *moov = atoms->find("moov");
if(!moov) {
debug("MP4: Atom 'moov' not found");
return;
}
MP4::Atom *trak = 0;
ByteVector data;
const MP4::AtomList trakList = moov->findall("trak");
for(MP4::AtomList::ConstIterator it = trakList.begin(); it != trakList.end(); ++it) {
trak = *it;
MP4::Atom *hdlr = trak->find("mdia", "hdlr");
if(!hdlr) {
debug("MP4: Atom 'trak.mdia.hdlr' not found");
return;
}
file->seek(hdlr->offset);
data = file->readBlock(static_cast<size_t>(hdlr->length));
if(data.containsAt("soun", 16)) {
break;
}
trak = 0;
}
if(!trak) {
debug("MP4: No audio tracks");
return;
}
MP4::Atom *mdhd = trak->find("mdia", "mdhd");
if(!mdhd) {
debug("MP4: Atom 'trak.mdia.mdhd' not found");
return;
}
file->seek(mdhd->offset);
data = file->readBlock(static_cast<size_t>(mdhd->length));
const unsigned int version = data[8];
long long unit;
long long length;
if(version == 1) {
if(data.size() < 36 + 8) {
debug("MP4: Atom 'trak.mdia.mdhd' is smaller than expected");
return;
}
unit = data.toInt64BE(28);
length = data.toInt64BE(36);
}
else {
if(data.size() < 24 + 4) {
debug("MP4: Atom 'trak.mdia.mdhd' is smaller than expected");
return;
}
unit = data.toUInt32BE(20);
length = data.toUInt32BE(24);
}
if(unit > 0 && length > 0)
d->length = static_cast<int>(length * 1000.0 / unit + 0.5);
MP4::Atom *atom = trak->find("mdia", "minf", "stbl", "stsd");
if(!atom) {
return;
}
file->seek(atom->offset);
data = file->readBlock(static_cast<size_t>(atom->length));
if(data.containsAt("mp4a", 20)) {
d->codec = AAC;
d->channels = data.toUInt16BE(40);
d->bitsPerSample = data.toUInt16BE(42);
d->sampleRate = data.toUInt32BE(46);
if(data.containsAt("esds", 56) && data[64] == 0x03) {
unsigned int pos = 65;
if(data.containsAt("\x80\x80\x80", pos)) {
pos += 3;
}
pos += 4;
if(data[pos] == 0x04) {
pos += 1;
if(data.containsAt("\x80\x80\x80", pos)) {
pos += 3;
}
pos += 10;
d->bitrate = static_cast<int>((data.toUInt32BE(pos) + 500) / 1000.0 + 0.5);
}
}
}
else if(data.containsAt("alac", 20)) {
if(atom->length == 88 && data.containsAt("alac", 56)) {
d->codec = ALAC;
d->bitsPerSample = data.at(69);
d->channels = data.at(73);
d->bitrate = static_cast<int>(data.toUInt32BE(80) / 1000.0 + 0.5);
d->sampleRate = data.toUInt32BE(84);
}
}
MP4::Atom *drms = atom->find("drms");
if(drms) {
d->encrypted = true;
}
}
