3eceaf4669
Bug: b/258408932 Change-Id: Ib96f39fe0c3912f9746bcc09d079097a145d6115 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/290987 Reviewed-by: Harald Alvestrand <hta@webrtc.org> Commit-Queue: Artem Titov <titovartem@webrtc.org> Cr-Commit-Position: refs/heads/main@{#39205}
60 lines
2.6 KiB
Markdown
60 lines
2.6 KiB
Markdown
<!-- go/cmark -->
|
|
<!--* freshness: {owner: 'hta' reviewed: '2021-05-07'} *-->
|
|
|
|
# PeerConnection and friends
|
|
|
|
The PeerConnection is the C++-level implementation of the Javascript
|
|
object "RTCPeerConnection" from the
|
|
[WEBRTC specification](https://w3c.github.io/webrtc-pc/).
|
|
|
|
Like many objects in WebRTC, the PeerConnection is used via a factory and an
|
|
observer:
|
|
|
|
* PeerConnectionFactory, which is created via a static Create method and takes
|
|
a PeerConnectionFactoryDependencies structure listing such things as
|
|
non-default threads and factories for use by all PeerConnections using
|
|
the same factory. (Using more than one factory should be avoided, since
|
|
it takes more resources.)
|
|
* PeerConnection itself, which is created by the method called
|
|
PeerConnectionFactory::CreatePeerConnectionOrError, and takes a
|
|
PeerConnectionInterface::RTCConfiguration argument, as well as
|
|
a PeerConnectionDependencies (even more factories, plus other stuff).
|
|
* PeerConnectionObserver (a member of PeerConnectionDependencies), which
|
|
contains the functions that will be called on events in the PeerConnection
|
|
|
|
These types are visible in the API.
|
|
|
|
## Internal structure of PeerConnection and friends
|
|
|
|
The PeerConnection is, to a large extent, a "God object" - most things
|
|
that are done in WebRTC require a PeerConnection.
|
|
|
|
Internally, it is divided into several objects, each with its own
|
|
responsibilities, all of which are owned by the PeerConnection and live
|
|
as long as the PeerConnection:
|
|
|
|
* SdpOfferAnswerHandler takes care of negotiating configurations with
|
|
a remote peer, using SDP-formatted descriptions.
|
|
* RtpTransmissionManager takes care of the lists of RtpSenders,
|
|
RtpReceivers and RtpTransceivers that form the heart of the transmission
|
|
service.
|
|
* DataChannelController takes care of managing the PeerConnection's
|
|
DataChannels and its SctpTransport.
|
|
* JsepTransportController takes care of configuring the details of senders
|
|
and receivers.
|
|
* Call does management of overall call state.
|
|
* RtcStatsCollector (and its obsolete sibling, StatsCollector) collects
|
|
statistics from all the objects comprising the PeerConnection when
|
|
requested.
|
|
|
|
There are a number of other smaller objects that are also owned by
|
|
the PeerConnection, but it would take too much space to describe them
|
|
all here; please consult the .h files.
|
|
|
|
PeerConnectionFactory owns an object called ConnectionContext, and a
|
|
reference to this is passed to each PeerConnection. It is referenced
|
|
via an rtc::scoped_refptr, which means that it is guaranteed to be
|
|
alive as long as either the factory or one of the PeerConnections
|
|
is using it.
|
|
|