def move_header_to_front(f):
aftype, amoov, alist = read_iso_file(f)
moov_idx = find_atom(alist, 'moov')
mdat_idx = find_atom(alist, 'mdat')
if moov_idx < mdat_idx:
# nothing to be done
return None
adict = atoms.atoms_dict(alist)
mdat = alist[mdat_idx]
new_moov_idx = mdat_idx
if 'wide' in adict:
# if 'wide' atom preceeds 'mdat', let's keep it that way
for wide in adict['wide']:
if wide.offset + wide.size == mdat.offset:
new_moov_idx -= 1
break
# for the moment assuming rewriting offsets in moov won't change
# the atoms sizes - could happen if:
# 2**32 - 1 - last_chunk_offset < moov.size
data_offset = amoov.get_size()
change_chunk_offsets(amoov, data_offset)
del alist[moov_idx]
alist[new_moov_idx:new_moov_idx] = [amoov]
return alist
def read_iso_file(fobj):
fobj.seek(0)
al = list(atoms.read_atoms(fobj))
ad = atoms.atoms_dict(al)
aftyp, amoov, mdat = select_atoms(ad, ('ftyp', 1, 1), ('moov', 1, 1),
('mdat', 1, None))
# print '(first mdat offset: %d)' % mdat[0].offset
return aftyp, amoov, al