mutagen/mp4.py
def __update_parents(self, fileobj, path, delta):
        """Update all parent atoms with the new size."""
        for atom in path:
            fileobj.seek(atom.offset)
            size = cdata.uint_be(fileobj.read(4))
            if size == 1:  # 64bit
                # skip name (4B) and read size (8B)
                size = cdata.ulonglong_be(fileobj.read(12)[4:])
                fileobj.seek(atom.offset + 8)
                fileobj.write(cdata.to_ulonglong_be(size + delta))
            else:  # 32bit
                fileobj.seek(atom.offset)
                fileobj.write(cdata.to_uint_be(size + delta))
def __update_parents(self, fileobj, path, delta):
        """Update all parent atoms with the new size."""
        for atom in path:
            fileobj.seek(atom.offset)
            size = cdata.uint_be(fileobj.read(4))
            if size == 1:  # 64bit
                # skip name (4B) and read size (8B)
                size = cdata.ulonglong_be(fileobj.read(12)[4:])
                fileobj.seek(atom.offset + 8)
                fileobj.write(cdata.to_ulonglong_be(size + delta))
            else:  # 32bit
                fileobj.seek(atom.offset)
                fileobj.write(cdata.to_uint_be(size + delta))
Update all parent atoms with the new size.