private void setHeader() {
// create the atoms needed to build the header.
Atom a_ftyp = getFTYPAtom();
Atom a_moov = getMOOVAtom();
Atom a_mdat = new Atom("mdat"); // create an empty atom. The AAC stream data should follow
// immediately after. The correct size will be set later.
// set the correct chunk offset in the stco atom.
Atom a_stco = a_moov.getChild("trak.mdia.minf.stbl.stco");
if (a_stco == null) {
mHeader = null;
return;
}
byte[] data = a_stco.getData();
int chunk_offset = a_ftyp.getSize() + a_moov.getSize() + a_mdat.getSize();
int offset = data.length - 4; // here stco should contain only one chunk offset.
data[offset++] = (byte) ((chunk_offset >> 24) & 0xFF);
data[offset++] = (byte) ((chunk_offset >> 16) & 0xFF);
data[offset++] = (byte) ((chunk_offset >> 8) & 0xFF);
data[offset++] = (byte) (chunk_offset & 0xFF);
// create the header byte array based on the previous atoms.
byte[] header = new byte[chunk_offset]; // here chunk_offset is also the size of the header
offset = 0;
for (Atom atom : new Atom[] {a_ftyp, a_moov, a_mdat}) {
byte[] atom_bytes = atom.getBytes();
System.arraycopy(atom_bytes, 0, header, offset, atom_bytes.length);
offset += atom_bytes.length;
}
// set the correct size of the mdat atom
int size = 8 + mTotSize;
offset -= 8;
header[offset++] = (byte) ((size >> 24) & 0xFF);
header[offset++] = (byte) ((size >> 16) & 0xFF);
header[offset++] = (byte) ((size >> 8) & 0xFF);
header[offset++] = (byte) (size & 0xFF);
mHeader = header;
}
// set the size field of the atom based on its content.
private void setSize() {
int size = 8; // type + size
if (mVersion >= 0) {
size += 4; // version + flags
}
if (mData != null) {
size += mData.length;
} else if (mChildren != null) {
for (Atom child : mChildren) {
size += child.getSize();
}
}
mSize = size;
}