def __init__(self, atoms, fileobj):
for trak in list(atoms["moov"].findall("trak")):
hdlr = trak["mdia", "hdlr"]
fileobj.seek(hdlr.offset)
data = fileobj.read(hdlr.length)
if data[16:20] == "soun":
break
else:
raise MP4StreamInfoError("track has no audio data")
mdhd = trak["mdia", "mdhd"]
fileobj.seek(mdhd.offset)
data = fileobj.read(mdhd.length)
if ord(data[8]) == 0:
offset = 20
fmt = ">2I"
else:
offset = 28
fmt = ">IQ"
end = offset + struct.calcsize(fmt)
unit, length = struct.unpack(fmt, data[offset:end])
self.length = float(length) / unit
try:
atom = trak["mdia", "minf", "stbl", "stsd"]
fileobj.seek(atom.offset)
data = fileobj.read(atom.length)
if data[20:24] == "mp4a":
length = cdata.uint_be(data[16:20])
(self.channels, self.bits_per_sample, _,
self.sample_rate) = struct.unpack(">3HI", data[40:50])
# ES descriptor type
if data[56:60] == "esds" and ord(data[64:65]) == 0x03:
pos = 65
# skip extended descriptor type tag, length, ES ID
# and stream priority
if data[pos:pos + 3] == "\x80\x80\x80":
pos += 3
pos += 4
# decoder config descriptor type
if ord(data[pos]) == 0x04:
pos += 1
# skip extended descriptor type tag, length,
# object type ID, stream type, buffer size
# and maximum bitrate
if data[pos:pos + 3] == "\x80\x80\x80":
pos += 3
pos += 10
# average bitrate
self.bitrate = cdata.uint_be(data[pos:pos + 4])
except (ValueError, KeyError):
# stsd atoms are optional
pass
def __parse_freeform(self, atom, data):
length = cdata.uint_be(data[:4])
mean = data[12:length]
pos = length
length = cdata.uint_be(data[pos:pos + 4])
name = data[pos + 12:pos + length]
pos += length
value = []
while pos < atom.length - 8:
length, atom_name = struct.unpack(">I4s", data[pos:pos + 8])
if atom_name != "data":
raise MP4MetadataError(
"unexpected atom %r inside %r" % (atom_name, atom.name))
value.append(data[pos + 16:pos + length])
pos += length
if value:
self["%s:%s:%s" % (atom.name, mean, name)] = value
def __update_offset_table(self, fileobj, fmt, atom, delta, offset):
"""Update offset table in the specified atom."""
if atom.offset > offset:
atom.offset += delta
fileobj.seek(atom.offset + 12)
data = fileobj.read(atom.length - 12)
fmt = fmt % cdata.uint_be(data[:4])
offsets = struct.unpack(fmt, data[4:])
offsets = [o + (0, delta)[offset < o] for o in offsets]
fileobj.seek(atom.offset + 16)
fileobj.write(struct.pack(fmt, *offsets))
def __update_tfhd(self, fileobj, atom, delta, offset):
if atom.offset > offset:
atom.offset += delta
fileobj.seek(atom.offset + 9)
data = fileobj.read(atom.length - 9)
flags = cdata.uint_be("\x00" + data[:3])
if flags & 1:
o = cdata.ulonglong_be(data[7:15])
if o > offset:
o += delta
fileobj.seek(atom.offset + 16)
fileobj.write(cdata.to_ulonglong_be(o))
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))