def __init__(self, atom, fileobj):
if atom.name not in (b"mp4a", b"alac"):
raise ValueError("Unsupported coding name %s" % atom.name)
ok, data = atom.read(fileobj)
if not ok or len(data) < 28:
raise ValueError("too short %s atom" % atom.name)
# SampleEntry
off = 6 # reserved
off += 2 # data_ref_index
# AudioSampleEntry
off += 8 # reserved
self.channels, off = cdata.uint16_be_from(data, off)
self.sample_size, off = cdata.uint16_be_from(data, off)
off += 2 # pre_defined
off += 2 # reserved
sample_rate, off = cdata.uint32_be_from(data, off)
# defined as Q16.16, but the fraction part seems unused..
# self.sample_rate = sample_rate * 2 ** (-16)
self.sample_rate = sample_rate >> 16
assert off == 28
fileobj = cBytesIO(data[off:])
try:
extra = Atom(fileobj)
except MP4MetadataError as e:
raise ValueError(e)
# esds only in mp4a atoms
if atom.name == b"mp4a" and extra.name == b"esds":
self._parse_esds(extra, fileobj)
elif atom.name == b"alac" and extra.name == b"alac":
self._parse_alac(extra, fileobj)
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 __init__(self, fileobj):
"""Reads the VBRI header or raises VBRIHeaderError.
The file position is undefined after this returns
"""
data = fileobj.read(26)
if len(data) != 26 or not data.startswith(b"VBRI"):
raise VBRIHeaderError("Not a VBRI header")
offset = 4
self.version, offset = cdata.uint16_be_from(data, offset)
if self.version != 1:
raise VBRIHeaderError(
"Unsupported header version: %r" % self.version)
offset += 2 # float16.. can't do
self.quality, offset = cdata.uint16_be_from(data, offset)
self.bytes, offset = cdata.uint32_be_from(data, offset)
self.frames, offset = cdata.uint32_be_from(data, offset)
toc_num_entries, offset = cdata.uint16_be_from(data, offset)
self.toc_scale_factor, offset = cdata.uint16_be_from(data, offset)
toc_entry_size, offset = cdata.uint16_be_from(data, offset)
self.toc_frames, offset = cdata.uint16_be_from(data, offset)
toc_size = toc_entry_size * toc_num_entries
toc_data = fileobj.read(toc_size)
if len(toc_data) != toc_size:
raise VBRIHeaderError("VBRI header truncated")
self.toc = []
if toc_entry_size == 2:
unpack = partial(cdata.uint16_be_from, toc_data)
elif toc_entry_size == 4:
unpack = partial(cdata.uint32_be_from, toc_data)
else:
raise VBRIHeaderError("Invalid TOC entry size")
self.toc = [unpack(i)[0] for i in xrange(0, toc_size, toc_entry_size)]
