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import asyncio
import logging
import random
import time
import traceback
import uuid
from typing import Callable, Dict, List, Optional, Union
from av import AudioFrame
from av.frame import Frame
from . import clock, rtp
from .codecs import get_capabilities, get_encoder, is_rtx
from .codecs.base import Encoder
from .exceptions import InvalidStateError
from .mediastreams import MediaStreamError, MediaStreamTrack
from .rtcrtpparameters import RTCRtpCodecParameters, RTCRtpSendParameters
from .rtp import (
RTCP_PSFB_APP,
RTCP_PSFB_PLI,
RTCP_RTPFB_NACK,
RTP_HISTORY_SIZE,
AnyRtcpPacket,
RtcpByePacket,
RtcpPsfbPacket,
RtcpRrPacket,
RtcpRtpfbPacket,
RtcpSdesPacket,
RtcpSenderInfo,
RtcpSourceInfo,
RtcpSrPacket,
RtpPacket,
unpack_remb_fci,
wrap_rtx,
)
from .stats import (
RTCOutboundRtpStreamStats,
RTCRemoteInboundRtpStreamStats,
RTCStatsReport,
)
from .utils import random16, random32, uint16_add, uint32_add
logger = logging.getLogger(__name__)
RTT_ALPHA = 0.85
def random_sequence_number() -> int:
"""
Generate a random RTP sequence number.
The sequence number is chosen in the lower half of the allowed range in
order to avoid wraparounds which break SRTP decryption.
See:
https://chromiumdash.appspot.com/commit/13b327b05fa3788b4daa9c3463e13282824cb320
"""
return random16() % 32768
class RTCEncodedFrame:
def __init__(self, payloads: List[bytes], timestamp: int, audio_level: int):
self.payloads = payloads
self.timestamp = timestamp
self.audio_level = audio_level
class RTCRtpSender:
"""
The :class:`RTCRtpSender` interface provides the ability to control and
obtain details about how a particular :class:`MediaStreamTrack` is encoded
and sent to a remote peer.
:param trackOrKind: Either a :class:`MediaStreamTrack` instance or a
media kind (`'audio'` or `'video'`).
:param transport: An :class:`RTCDtlsTransport`.
"""
def __init__(self, trackOrKind: Union[MediaStreamTrack, str], transport) -> None:
if transport.state == "closed":
raise InvalidStateError
if isinstance(trackOrKind, MediaStreamTrack):
self.__kind = trackOrKind.kind
self.replaceTrack(trackOrKind)
else:
self.__kind = trackOrKind
self.replaceTrack(None)
self.__cname: Optional[str] = None
self._ssrc = random32()
self._rtx_ssrc = random32()
# FIXME: how should this be initialised?
self._stream_id = str(uuid.uuid4())
self._enabled = True
self.__encoder: Optional[Encoder] = None
self.__force_keyframe = False
self.__loop = asyncio.get_event_loop()
self.__mid: Optional[str] = None
self.__rtp_exited = asyncio.Event()
self.__rtp_header_extensions_map = rtp.HeaderExtensionsMap()
self.__rtp_started = asyncio.Event()
self.__rtp_task: Optional[asyncio.Future[None]] = None
self.__rtp_history: Dict[int, RtpPacket] = {}
self.__rtcp_exited = asyncio.Event()
self.__rtcp_started = asyncio.Event()
self.__rtcp_task: Optional[asyncio.Future[None]] = None
self.__rtx_payload_type: Optional[int] = None
self.__rtx_sequence_number = random_sequence_number()
self.__started = False
self.__stats = RTCStatsReport()
self.__transport = transport
# stats
self.__lsr: Optional[int] = None
self.__lsr_time: Optional[float] = None
self.__ntp_timestamp = 0
self.__rtp_timestamp = 0
self.__octet_count = 0
self.__packet_count = 0
self.__rtt: Optional[float] = None
# logging
self.__log_debug: Callable[..., None] = lambda *args: None
if logger.isEnabledFor(logging.DEBUG):
self.__log_debug = lambda msg, *args: logger.debug(
f"RTCRtpSender(%s) {msg}", self.__kind, *args
)
@property
def kind(self):
return self.__kind
@property
def track(self) -> MediaStreamTrack:
"""
The :class:`MediaStreamTrack` which is being handled by the sender.
"""
return self.__track
@property
def transport(self):
"""
The :class:`RTCDtlsTransport` over which media data for the track is
transmitted.
"""
return self.__transport
@classmethod
def getCapabilities(self, kind):
"""
Returns the most optimistic view of the system's capabilities for
sending media of the given `kind`.
:rtype: :class:`RTCRtpCapabilities`
"""
return get_capabilities(kind)
async def getStats(self) -> RTCStatsReport:
"""
Returns statistics about the RTP sender.
:rtype: :class:`RTCStatsReport`
"""
self.__stats.add(
RTCOutboundRtpStreamStats(
# RTCStats
timestamp=clock.current_datetime(),
type="outbound-rtp",
id="outbound-rtp_" + str(id(self)),
# RTCStreamStats
ssrc=self._ssrc,
kind=self.__kind,
transportId=self.transport._stats_id,
# RTCSentRtpStreamStats
packetsSent=self.__packet_count,
bytesSent=self.__octet_count,
# RTCOutboundRtpStreamStats
trackId=str(id(self.track)),
)
)
self.__stats.update(self.transport._get_stats())
return self.__stats
def replaceTrack(self, track: Optional[MediaStreamTrack]) -> None:
self.__track = track
if track is not None:
self._track_id = track.id
else:
self._track_id = str(uuid.uuid4())
def setTransport(self, transport) -> None:
self.__transport = transport
async def send(self, parameters: RTCRtpSendParameters) -> None:
"""
Attempt to set the parameters controlling the sending of media.
:param parameters: The :class:`RTCRtpSendParameters` for the sender.
"""
if not self.__started:
self.__cname = parameters.rtcp.cname
self.__mid = parameters.muxId
# make note of the RTP header extension IDs
self.__transport._register_rtp_sender(self, parameters)
self.__rtp_header_extensions_map.configure(parameters)
# make note of RTX payload type
for codec in parameters.codecs:
if (
is_rtx(codec)
and codec.parameters["apt"] == parameters.codecs[0].payloadType
):
self.__rtx_payload_type = codec.payloadType
break
self.__rtp_task = asyncio.ensure_future(self._run_rtp(parameters.codecs[0]))
self.__rtcp_task = asyncio.ensure_future(self._run_rtcp())
self.__started = True
async def stop(self) -> None:
"""
Irreversibly stop the sender.
"""
if self.__started:
self.__transport._unregister_rtp_sender(self)
# shutdown RTP and RTCP tasks
await asyncio.gather(self.__rtp_started.wait(), self.__rtcp_started.wait())
self.__rtp_task.cancel()
self.__rtcp_task.cancel()
await asyncio.gather(self.__rtp_exited.wait(), self.__rtcp_exited.wait())
async def _handle_rtcp_packet(self, packet) -> None:
if isinstance(packet, (RtcpRrPacket, RtcpSrPacket)):
for report in filter(lambda x: x.ssrc == self._ssrc, packet.reports):
# estimate round-trip time
if self.__lsr == report.lsr and report.dlsr:
rtt = time.time() - self.__lsr_time - (report.dlsr / 65536)
if self.__rtt is None:
self.__rtt = rtt
else:
self.__rtt = RTT_ALPHA * self.__rtt + (1 - RTT_ALPHA) * rtt
self.__stats.add(
RTCRemoteInboundRtpStreamStats(
# RTCStats
timestamp=clock.current_datetime(),
type="remote-inbound-rtp",
id="remote-inbound-rtp_" + str(id(self)),
# RTCStreamStats
ssrc=packet.ssrc,
kind=self.__kind,
transportId=self.transport._stats_id,
# RTCReceivedRtpStreamStats
packetsReceived=self.__packet_count - report.packets_lost,
packetsLost=report.packets_lost,
jitter=report.jitter,
# RTCRemoteInboundRtpStreamStats
roundTripTime=self.__rtt,
fractionLost=report.fraction_lost,
)
)
elif isinstance(packet, RtcpRtpfbPacket) and packet.fmt == RTCP_RTPFB_NACK:
for seq in packet.lost:
await self._retransmit(seq)
elif isinstance(packet, RtcpPsfbPacket) and packet.fmt == RTCP_PSFB_PLI:
self._send_keyframe()
elif isinstance(packet, RtcpPsfbPacket) and packet.fmt == RTCP_PSFB_APP:
try:
bitrate, ssrcs = unpack_remb_fci(packet.fci)
if self._ssrc in ssrcs:
self.__log_debug(
"- receiver estimated maximum bitrate %d bps", bitrate
)
if self.__encoder and hasattr(self.__encoder, "target_bitrate"):
self.__encoder.target_bitrate = bitrate
except ValueError:
pass
async def _next_encoded_frame(
self, codec: RTCRtpCodecParameters
) -> Optional[RTCEncodedFrame]:
# Get [Frame|Packet].
data = await self.__track.recv()
# If the sender is disabled, drop the frame instead of encoding it.
# We still want to read from the track in order to avoid frames
# accumulating in memory.
if not self._enabled:
return None
audio_level = None
if self.__encoder is None:
self.__encoder = get_encoder(codec)
if isinstance(data, Frame):
# Encode the frame.
if isinstance(data, AudioFrame):
audio_level = rtp.compute_audio_level_dbov(data)
force_keyframe = self.__force_keyframe
self.__force_keyframe = False
payloads, timestamp = await self.__loop.run_in_executor(
None, self.__encoder.encode, data, force_keyframe
)
else:
# Pack the pre-encoded data.
payloads, timestamp = self.__encoder.pack(data)
# If the encoder did not return any payloads, return `None`.
# This may be due to a delay caused by resampling.
if not payloads:
return None
return RTCEncodedFrame(payloads, timestamp, audio_level)
async def _retransmit(self, sequence_number: int) -> None:
"""
Retransmit an RTP packet which was reported as lost.
"""
packet = self.__rtp_history.get(sequence_number % RTP_HISTORY_SIZE)
if packet and packet.sequence_number == sequence_number:
if self.__rtx_payload_type is not None:
packet = wrap_rtx(
packet,
payload_type=self.__rtx_payload_type,
sequence_number=self.__rtx_sequence_number,
ssrc=self._rtx_ssrc,
)
self.__rtx_sequence_number = uint16_add(self.__rtx_sequence_number, 1)
self.__log_debug("> %s", packet)
packet_bytes = packet.serialize(self.__rtp_header_extensions_map)
await self.transport._send_rtp(packet_bytes)
def _send_keyframe(self) -> None:
"""
Request the next frame to be a keyframe.
"""
self.__force_keyframe = True
async def _run_rtp(self, codec: RTCRtpCodecParameters) -> None:
self.__log_debug("- RTP started")
self.__rtp_started.set()
sequence_number = random_sequence_number()
timestamp_origin = random32()
try:
while True:
if not self.__track:
await asyncio.sleep(0.02)
continue
# Fetch the next encoded frame. This can be `None` if the sender
# is disabled, in which case we just continue the loop.
enc_frame = await self._next_encoded_frame(codec)
if enc_frame is None:
continue
timestamp = uint32_add(timestamp_origin, enc_frame.timestamp)
for i, payload in enumerate(enc_frame.payloads):
packet = RtpPacket(
payload_type=codec.payloadType,
sequence_number=sequence_number,
timestamp=timestamp,
)
packet.ssrc = self._ssrc
packet.payload = payload
packet.marker = (i == len(enc_frame.payloads) - 1) and 1 or 0
# set header extensions
packet.extensions.abs_send_time = (
clock.current_ntp_time() >> 14
) & 0x00FFFFFF
packet.extensions.mid = self.__mid
if enc_frame.audio_level is not None:
packet.extensions.audio_level = (False, -enc_frame.audio_level)
# send packet
self.__log_debug("> %s", packet)
self.__rtp_history[packet.sequence_number % RTP_HISTORY_SIZE] = (
packet
)
packet_bytes = packet.serialize(self.__rtp_header_extensions_map)
await self.transport._send_rtp(packet_bytes)
self.__ntp_timestamp = clock.current_ntp_time()
self.__rtp_timestamp = packet.timestamp
self.__octet_count += len(payload)
self.__packet_count += 1
sequence_number = uint16_add(sequence_number, 1)
except (asyncio.CancelledError, ConnectionError, MediaStreamError):
pass
except Exception:
# we *need* to set __rtp_exited, otherwise RTCRtpSender.stop() will hang,
# so issue a warning if we hit an unexpected exception
self.__log_warning(traceback.format_exc())
# stop track
if self.__track:
self.__track.stop()
self.__track = None
# release encoder
self.__encoder = None
self.__log_debug("- RTP finished")
self.__rtp_exited.set()
async def _run_rtcp(self) -> None:
self.__log_debug("- RTCP started")
self.__rtcp_started.set()
try:
while True:
# The interval between RTCP packets is varied randomly over the
# range [0.5, 1.5] times the calculated interval.
await asyncio.sleep(0.5 + random.random())
# RTCP SR
packets: List[AnyRtcpPacket] = [
RtcpSrPacket(
ssrc=self._ssrc,
sender_info=RtcpSenderInfo(
ntp_timestamp=self.__ntp_timestamp,
rtp_timestamp=self.__rtp_timestamp,
packet_count=self.__packet_count,
octet_count=self.__octet_count,
),
)
]
self.__lsr = ((self.__ntp_timestamp) >> 16) & 0xFFFFFFFF
self.__lsr_time = time.time()
# RTCP SDES
if self.__cname is not None:
packets.append(
RtcpSdesPacket(
chunks=[
RtcpSourceInfo(
ssrc=self._ssrc,
items=[(1, self.__cname.encode("utf8"))],
)
]
)
)
await self._send_rtcp(packets)
except asyncio.CancelledError:
pass
# RTCP BYE
packet = RtcpByePacket(sources=[self._ssrc])
await self._send_rtcp([packet])
self.__log_debug("- RTCP finished")
self.__rtcp_exited.set()
async def _send_rtcp(self, packets: List[AnyRtcpPacket]) -> None:
payload = b""
for packet in packets:
self.__log_debug("> %s", packet)
payload += bytes(packet)
try:
await self.transport._send_rtp(payload)
except ConnectionError:
pass
def __log_warning(self, msg: str, *args) -> None:
logger.warning(f"RTCRtpsender(%s) {msg}", self.__kind, *args)
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