def _parse_esds(self, esds, fileobj):
assert esds.name == b"esds"
ok, data = esds.read(fileobj)
if not ok:
raise ValueError("truncated %s atom" % esds.name)
version, flags, data = _parse_full_atom(data)
if version != 0:
# unsupported version, ignore
return
try:
tag, off = cdata.uint8_from(data, 0)
ES_DescrTag = 0x03
if tag != ES_DescrTag:
raise ValueError("unexpected descriptor: %d" % tag)
base_size, off = _parse_desc_length(data, off)
es_id, off = cdata.uint16_be_from(data, off)
es_flags, off = cdata.uint8_from(data, off)
streamDependenceFlag = cdata.test_bit(es_flags, 7)
URL_Flag = cdata.test_bit(es_flags, 6)
OCRstreamFlag = cdata.test_bit(es_flags, 5)
# streamPriority = es_flags & 0x1f
if streamDependenceFlag:
off += 2 # dependsOn_ES_ID
if URL_Flag:
url_len, off = cdata.uint8_from(data, off)
off += url_len # URLstring
if OCRstreamFlag:
off += 2 # OCR_ES_Id
DecoderConfigDescrTag = 4
tag, off = cdata.uint8_from(data, off)
if tag != DecoderConfigDescrTag:
raise ValueError("unexpected DecoderConfigDescrTag %d" % tag)
dec_conf_size, off = _parse_desc_length(data, off)
off += 9 # skip some stuff
# average bitrate
self.bitrate, off = cdata.uint32_be_from(data, off)
except cdata.error as e:
raise ValueError(e)
def _parse_desc_length(data, offset):
"""Returns the decoded value and the new offset in data after the value.
Can raise ValueError in case the value is too long or data too short.
"""
value = 0
for i in xrange(4):
try:
b, offset = cdata.uint8_from(data, offset)
except cdata.error as e:
raise ValueError(e)
value = (value << 7) | (b & 0x7f)
if not b >> 7:
break
else:
raise ValueError("invalid descriptor length")
return value, offset
def _parse_alac(self, atom, fileobj):
# https://alac.macosforge.org/trac/browser/trunk/
# ALACMagicCookieDescription.txt
assert atom.name == b"alac"
ok, data = atom.read(fileobj)
if not ok:
raise ValueError("truncated %s atom" % atom.name)
version, flags, data = _parse_full_atom(data)
if version != 0:
# unsupported version, ignore
return
# for some files the AudioSampleEntry values default to 44100/2chan
# and the real info is in the alac cookie, so prefer it
try:
self.channels, off = cdata.uint8_from(data, 9)
off += 6 # skip some stuff
self.bitrate, off = cdata.uint32_be_from(data, off)
self.sample_rate, off = cdata.uint32_be_from(data, off)
except cdata.error as e:
raise ValueError(e)