The Real-time Transport Protocol (RTP) is a widely used network protocol for transmitting audio or video. It usually works with the RTP Control Protocol (RTCP). The transmission can be based on Transmission Control Protocol (TCP) or User Datagram Protocol (UDP).
This page hosts a formal specification of RTP (Real-time Transport Protocol) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = RtpPacket.from_file("path/to/local/file.bin")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = RtpPacket(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.data # => Payload without padding.
data.len_padding_if_exists # => If padding bit is enabled, last byte of data contains number of
bytes appended to the payload as padding.
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class RtpPacket(KaitaiStruct):
"""The Real-time Transport Protocol (RTP) is a widely used network
protocol for transmitting audio or video. It usually works with the
RTP Control Protocol (RTCP). The transmission can be based on
Transmission Control Protocol (TCP) or User Datagram Protocol (UDP).
"""
class PayloadTypeEnum(Enum):
pcmu = 0
reserved1 = 1
reserved2 = 2
gsm = 3
g723 = 4
dvi4_1 = 5
dvi4_2 = 6
lpc = 7
pcma = 8
g722 = 9
l16_1 = 10
l16_2 = 11
qcelp = 12
cn = 13
mpa = 14
g728 = 15
dvi4_3 = 16
dvi4_4 = 17
g729 = 18
reserved19 = 19
unassigned20 = 20
unassigned21 = 21
unassigned22 = 22
unassigned23 = 23
unassigned24 = 24
celb = 25
jpeg = 26
unassigned27 = 27
nv = 28
unassigned29 = 29
unassigned30 = 30
h261 = 31
mpv = 32
mp2t = 33
h263 = 34
mpeg_ps = 96
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.version = self._io.read_bits_int_be(2)
self.has_padding = self._io.read_bits_int_be(1) != 0
self.has_extension = self._io.read_bits_int_be(1) != 0
self.csrc_count = self._io.read_bits_int_be(4)
self.marker = self._io.read_bits_int_be(1) != 0
self.payload_type = KaitaiStream.resolve_enum(RtpPacket.PayloadTypeEnum, self._io.read_bits_int_be(7))
self._io.align_to_byte()
self.sequence_number = self._io.read_u2be()
self.timestamp = self._io.read_u4be()
self.ssrc = self._io.read_u4be()
if self.has_extension:
self.header_extension = RtpPacket.HeaderExtention(self._io, self, self._root)
self.data = self._io.read_bytes(((self._io.size() - self._io.pos()) - self.len_padding))
self.padding = self._io.read_bytes(self.len_padding)
class HeaderExtention(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.id = self._io.read_u2be()
self.length = self._io.read_u2be()
@property
def len_padding_if_exists(self):
"""If padding bit is enabled, last byte of data contains number of
bytes appended to the payload as padding.
"""
if hasattr(self, '_m_len_padding_if_exists'):
return self._m_len_padding_if_exists
if self.has_padding:
_pos = self._io.pos()
self._io.seek((self._io.size() - 1))
self._m_len_padding_if_exists = self._io.read_u1()
self._io.seek(_pos)
return getattr(self, '_m_len_padding_if_exists', None)
@property
def len_padding(self):
"""Always returns number of padding bytes to in the payload."""
if hasattr(self, '_m_len_padding'):
return self._m_len_padding
self._m_len_padding = (self.len_padding_if_exists if self.has_padding else 0)
return getattr(self, '_m_len_padding', None)