Object RTC (ORTC) API for WebRTC
This document defines a set of ECMAScript APIs in WebIDL to allow media to be sent and received
from another browser or device implementing the appropriate set of real-time protocols. However,
unlike the current WebRTC 1.0 APIs, ORTC does not mandate a media signaling protocol or
format. As a result, ORTC does not utilize Session Description Protocol (SDP) within its APIs, nor does it mandate support for
the Offer/Answer state machine. Instead, ORTC focuses on "connections" and "tracks" being
carried over those connections.
Overview
Object RealTime Communications (ORTC) provides a powerful API for the development of WebRTC based applications.
ORTC does not mandate a media signaling protocol or format (as the current WebRTC 1.0 does by mandating SDP Offer/Answer).
Instead, ORTC focuses on "sender", "receiver" and "transport" objects, which have
"capabilities" describing what they are capable of doing,
as well as "parameters" which define what they are configured to do.
"Tracks" and "data channels" are sent over the transports, between senders and receivers.
This specification defines several objects: RTCDtlsTransport (Section 2), RTCIceTransport (Section 3),
RTCIceListener (Section 4), RTCRtpSender (Section 5), RTCRtpReceiver (Section 6),
RTCDTMFTrack (Section 8), RTCDataChannel
(Section 9), and RTCSctpTransport (Section 10); RTP dictionaries are described in Section 7.
In a Javascript application utilizing the ORTC API,
the relationship between the application and the objects, as well
as between the objects themselves is shown below:
Terminology
The
EventHandler
interface represents a callback used for event handlers as defined in
[[!HTML5]].
The concepts
queue a
task
and
fires a
simple event
are defined in [[!HTML5]].
The terms
event
event
handlers
and
event
handler event types
are defined in [[!HTML5]].
The terms
MediaStream
MediaStreamTrack
Constraints
, and
Consumer
are defined in
[[!GETUSERMEDIA]].
The RTCDtlsTransport Object
The
RTCDtlsTransport
includes information relating to Datagram Transport Layer Security (DTLS) transport.
Overview
An
RTCDtlsTransport
instance is associated to an
RTCRtpSender
or an
RTCRtpReceiver
Operation
RTCDtlsTransport
instance is optionally constructed from an
RTCIceTransport
object or an
RTCIceTransport
is automatically constructed.
Interface Definition
readonly attribute RTCIceTransport transport
The associated
RTCIceTransport
instance.
readonly attribute RTCDtlsTransportState state
The current state of the DTLS transport.
RTCDtlsParameters getLocalParameters()
Obtain the DTLS parameters of the local
RTCDtlsTransport
RTCDtlsParameters? getRemoteParameters()
Obtain the current DTLS parameters of the remote
RTCDtlsTransport
void start(RTCDtlsParameters remoteParameters)
Start DTLS transport negotiation with the parameters of the remote DTLS transport.
void stop()
Stops and closes the DTLS transport object.
attribute EventHandler? onstatechange
Set this handler to receive events when the state of the DTLS transport changes.
Example
enum RTCDtlsTransportState
new
new state
connecting
connecting state
connected
connected state
closed
closed state
The RTCIceTransport Object
The
RTCIceTransport
includes information relating to Interactive Connectivity Establishment (ICE).
Overview
An
RTCIceTransport
instance is associated to a transport object (such as RTCDtlsTransport),
and provides RTC related methods to it.
Operation
An
RTCIceTransport
instance is constructed from an
RTCIceRole
and either an
RTCIceListener
or an
RTCIceOptions
object.
Interface Definition
readonly attribute RTCIceRole role
The current role of the ICE transport.
readonly attribute RTCIceTransportState state
The current state of the ICE transport.
readonly attribute sequence
Sequence of the candidates associated with local
RTCIceTransport
readonly attribute sequence
Sequence of the candidates associated with remote
RTCIceTransport
void gather()
Start gathering
RTCIceCandidate
objects.
void start(optional RTCIceParameters remoteParameters)
Starts candidates connectivity checks and attempts to connect to the remote
RTCIceTransport
void stop()
Stops and closes the current object.
RTCIceParameters getLocalParameters()
Obtain the ICE parameters of the local
RTCIceTransport
RTCIceParameters? getRemoteParameters()
Obtain the current ICE parameters of the remote
RTCIceTransport
void setRemoteParameters(RTCIceParameters remoteParameters)
Set the remote parameters associated with the remote
RTCIceTransport
void addRemoteCandidate(RTCIceCandidate remoteCandidate)
Add remote candidate associated with remote
RTCIceTransport
attribute EventHandler? onlocalcandidate
Set this handler to receive events when a new local candidate is available.
attribute EventHandler? onstatechange
Set this handler to receive events when the state of the
RTCIceTransport
has changed.
Examples
// Assume we already have a way to signal. This is an example
// of how to offer ICE and DTLS parameters and ICE candidates and
// get back ICE and DTLS parameters and ICE candidates, and start
// both ICE and DTLS.
function initiate(signaller) {
var iceOptions = ...;
var ice = new RTCIceTransport(RTCIceRole.controlling, iceOptions);
var dtls = new RTCDtlsTransport(ice);
// ... get tracks and RTP objects from other example
signaller.sendInitiate({
"ice": ice.
getLocalParameters(),
"dtls": dtls.
getLocalParameters(),
// ... include RTP info from other example
}, function(remote) {
ice.setRemoteParameters(remote.ice);
dtls.start(remote.dtls);
// ... start RTP senders and receivers from other example
});
ice.oncandidate = function(candidate) {
signaller.sendLocalCandidate(candidate);
signaller.onRemoteCandidate = function(candidate) {
ice.addRemoteCandidate(candidate);
ice.start();
// Assume we already have a way to signal and remote info is
// signalled to us. This is an example of how to answer with ICE and DTLS
// and DTLS parameters and ICE candidates and start both ICE and DTLS.
//
function accept(signaller, remote) {
var iceOptions = ...;
var ice = new RTCIceTransport(iceOptions);
var dtls = new RTCDtlsTransport(ice);
// ... get tracks and RTP objects from other example
ice.oncandidate = function(candidate) {
signaller.sendLocalCandidate(candidate);
signaller.onRemoteCandidate = function(candidate) {
ice.addRemoteCandidate(candidate);
signaller.sendAccept({
"ice": ice.
getLocalParameters(),
"dtls": ice.
getLocalParameters()
// ... include RTP info from other example
});
ice.start(remote.ice);
dtls.start(remote.dtls);
// ... start RTP senders and receivers from other example
enum RTCIceRole
controlling
controlling state
controlled
controlled state
enum RTCIceTransportState
new
new state
checking
checking state
connected
connected state
completed
completed state
disconnected
disconnected state
closed
closed state
The non-normative ICE state transitions are:
The RTCIceOptions Object
The
RTCIceOptions
object includes information relating to ICE configuration.
sequence
An array containing STUN and TURN servers available to be used by ICE.
The RTCIceServer Object
The
RTCIceServer
is used to provide STUN or TURN server configuration. In network topologies with multiple layers of NATs, it is desirable to have a STUN server between every layer of NATs in addition to the TURN servers to minimize the peer to peer network latency.
An example of an array of RTCIceServer objects:
[ { urls: "stun:stun1.example.net } , { urls:"turn:turn.example.org", username: "user", credential:"myPassword"} ]
(DOMString or sequence
STUN or TURN URI(s) as defined in [[!STUN-URI]] and [[!TURN-URI]]
DOMString? username
If this RTCIceServer object represents a TURN server, then this attribute specifies the username to use with that TURN server.
DOMString? credential
If the uri element is a TURN-URI, then this is the credential to use with that TURN server.
The RTCIceCandidate Object
The
RTCIceCandidate
object includes information relating to an ICE candidate.
foundation: "abcd1234",
priority: 1694498815,
connectionAddress: "192.0.2.33",
connectionPort: 10000,
type: "host"
};
DOMString foundation
A unique identifier that allows ICE to correlate candidates that appear on multiple
RTCIceTransport
s.
unsigned long priority
The assigned priority of the candidate. This is automatically populated by the browser.
DOMString ip
The IP address of the candidate.
unsigned short port
The UDP port for the candidate.
RTCIceCandidateType type
The type of candidate.
DOMString? relatedAddress
For candidates that are derived from others, such as relay or reflexive candidates, this
refers to the host candidate that these are derived from. This value is not present on
host candidates.
unsigned short? relatedPort
For candidates that are derived from others, such as relay or reflexive candidates, this
refers to the host candidate that these are derived from. This value is not present on
host candidates.
The RTCIceCandidateType
The
RTCIceCandidateType
includes the type of ICE candidate.
host
A host candidate.
srflx
A server reflexive candidate.
prflx
A peer reflexive candidate.
relay
A relay candidate.
The RTCIceListener Object
The
RTCIceListener
enables an endpoint to construct multiple RTCIceTransport
objects from a set of local ICE parameters,
enabling usage scenarios such as parallel forking.
Overview
An
RTCIceListener
instance is associated to an
RTCIceTransport
Operation
An
RTCIceListener
instance is optionally constructed from an
RTCIceOptions
object,
or an
RTCIceListener
is automatically constructed.
Interface Definition
readonly attribute
RTCIceOptions
options
The
RTCIceOptions
instance.
RTCIceParameters
getLocalParameters()
readonly attribute sequence
void start()
void stop()
attribute EventHandler? onlocalcandidate
attribute EventHandler? ongatherfailure
Example
var iceOptions = ...;
var iceListener = new RTCIceListener(iceOptions);
sendInitiate(iceListener.getLocalParameters(), function(response) {
// We may get N responses
var ice = new RTCIceTransport(RTCIceRole.controlling, iceListener);
var ice.setRemoteParameters(response.iceParameters);
ice.start();
// ... setup DTLS, RTP, SCTP, etc.
});
iceListener.oncandidate = sendLocalCandidate;
iceListener.start();
The RTCRtpSender Object
The
RTCRtpSender
includes information relating to the RTP sender.
Overview
An
RTCRtpSender
instance is associated to a sending
MediaStreamTrack
and provides RTC related methods to it.
Operation
RTCRtpSender
instance is constructed from an
MediaStreamTrack
object and associated to an
RTCDtlsTransport
Interface Definition
attribute
MediaStreamTrack
track
The associated
MediaStreamTrack
instance.
attribute
RTCDtlsTransport
transport
The associated
RTCDtlsTransport
instance.
static
RTCRtpCapabilities
getCapabilities()
Obtain the capabilities of the
RTCRtpSender
static
RTCRtpParameters
createParameters(
MediaStreamTrack
parameters, optional
RTCRtpCapabilities
capabilities)
Create parameters based on the
MediaStreamTrack
and the capabilities specified in
RTCRtpCapabilities
static
RTCRtpParameters
filterParameters(
RTCRtpParameters
parameters, optional
RTCRtpCapabilities
capabilities)
Filter parameters based on the
RTCRtpCapabilities
void send(
RTCRtpParameters
parameters)
Media is controlled by the given "parameters". The sender starts sending when the send() is called and stopped when the stop() is called.
void stop()
Stops sending the track on the wire. Stop is final like
MediaStreamTrack
Example
The RTCRtpReceiver Object
The
RTCRtpReceiver
includes information relating to the RTP receiver.
Overview
An
RTCRtpReceiver
instance is associated to a sending
MediaStreamTrack
and provides RTC related methods to it.
Operation
RTCRtpReceiver
instance is constructed from an
MediaStreamTrack
object and associated to an
RTCDtlsTransport
Interface Definition
attribute
MediaStreamTrack
? track
The associated
MediaStreamTrack
instance.
attribute
RTCDtlsTransport
transport
The associated
RTCDtlsTransport
instance.
static
RTCRtpCapabilities
getCapabilities()
Obtain the capabilities of the
RTCRtpReceiver
static
RTCRtpParameters
createParameters (DOMString kind, optional RTCRtpCapabilities capabilities)
Create parameters based on the kind and the capabilities specified in
RTCRtpCapabilities
DOMString kind
Specifies kind, either "audio" or "video".
optional RTCRtpCapabilities capabilities
static
RTCRtpParameters
filterParameters(
RTCRtpParameters
parameters, optional
RTCRtpCapabilities
capabilities)
Filter parameters based on the
RTCRtpCapabilities
void receive(
RTCRtpParameters
parameters)
Media is controlled by the given "parameters". The receiver starts receiving when the receive() is called and stopped when the stop() is called.
void stop()
Stops receiving the track on the wire. Stop is final like
MediaStreamTrack
Examples
// Assume we already have a way to signal, a transport
// (RTCDtlsTransport), and audio and video tracks. This is an example
// of how to offer them and get back an answer with audio and
// video tracks, and begin sending and receiving them.
function initiate(signaller, transport, audioTrack, videoTrack) {
var audioSender = new RTCRtpSender(audioTrack, transport);
var videoSender = new RTCRtpSender(videoTrack, transport);
var audioReceiver = new RTCRtpReceiver(transport);
var videoReceiver = new RTCRtpReceiver(transport);
var sendAudioParams = RTCRtpSender.createParameters(audioTrack);
var sendVideoParams = RTCRtpSender.createParameters(videoTrack);
signaller.offerTracks({
// The initiator offers parameters it wants to send with,
// and the capabilities it has for receiving.
"rtpCaps": RTCRtpReceiver.getCapabilities(),
"audio": sendAudioParams,
"video": sendVideoParams
}, function(answer) {
// The responder answers with parameters it wants to send with
// and the capabilities it has for receiving.
audioSendParams = RTCRtpSender.filterParameters(
sendAudioParams, answer.rtpCaps);
videoSendParams = RTCRtpSender.filterParameters(
sendVideoParams, answer.rtpCaps
var audioRecvParams = RTCRtpSender.filterParameters(
answer.audio);
var videoRecvParams = RTCRtpSender.filterParameters(
answer.video);
audioSender.send(audioSendParams);
videoSender.send(videoSendParams)
audioReceiver.receive(audioRecvParams);
videoReceiver.receive(videoRecvParams);
// Now we can render/play
// audioReceiver.track and videoReceiver.track.
});
// Assume we already have a way to signal, a transport
// (RTCDtlsTransport), and audio and video tracks. This is an example
// of how to answer an offer with audio and video tracks, and begin
// sending and receiving them.
function accept(
signaller, remote, transport, audioTrack, videoTrack) {
var audioSender = new RTCRtpSender(audioTrack, transport);
var videoSender = new RTCRtpSender(videoTrack, transport);
var audioReceiver = new RTCRtpReceiver(transport);
var videoReceiver = new RTCRtpReceiver(transport);
var audioSendParams = RTCRtpSender.createParameters(
audioTrack, remote.rtpCaps);
var videoSendParams = RTCRtpSender.createParameters(
videoTrack, remote.rtpCaps);
var audioRecvParams = RTCRtpSender.filterParameters(
remote.audio);
var videoRecvParams = RTCRtpSender.filterParameters(
remote.video);
audioSender.send(audioSendParams);
videoSender.send(videoSendParams)
audioReceiver.receive(audioRecvParams);
videoReceiver.receive(videoRecvParams);
signaller.answerTracks({
"rtpCaps": RTCRtpReceiver.getCapabilities(),
"audio": audioSender.parameters(),
"video": videoSender.parameters()
});
// Now we can render/play
// audioReceiver.track and videoReceiver.track.
Dictionaries related to Rtp
dictionary RTCRtpCapabilities
sequence
Supported audio codecs.
sequence
Supported video codecs.
sequence
URIs of supported RTP header extensions.
sequence
Supported features.
dictionary RTCRtpCodec
DOMString name
MIME media type
unsigned byte? payload-id
Payload Type
unsigned int? clockRate
Codec clockrate
unsigned int? numChannels
sequence
Codec-specific format parameters.
dictionary RTCRtpCodecParameter
DOMString name
Name of the codec-specific parameter.
DOMString? value
Value of the codec-specific parameter.
enum RTCRtpFeatures
nack
From [[!RFC4585]]
dictionary RTCRtpParameters
sequence
sequence
Can specify multiple layers or "encodings" to be used for things like simulcast, RTC, FEC, etc.
sequence
Can specify RTP header extensions.
dictionary RTCRtpEncodingParameters
unsigned int ssrc
int TODO
Temporary placeholder for things to control various layers, simulcast, rtc, etc.
dictionary RTCRtpHeaderExtensionParameters
DOMString uri
The URI of the RTP header extension, as defined in [[!RFC5285]].
unsigned short id
The value that goes in the packet.
boolean encrypt
If true, encrypt the value in the header, as per [[!RFC6904]].
The RTCDtmfSender Object
Overview
An
RTCDtmfSender
instance allows sending DTMF tones to/from the remote peer.
Operation
An
RTCDtmfSender
object is constructed from an
RTCRtpSender
object.
Interface Definition
readonly attribute boolean
canInsertDTMF
Whether the
RTCDtmfSender
is capable of sending DTMF.
void insertDTMF(in DOMString tones, optional long duration, long
interToneGap)
readonly attribute
RTCRtpSender
sender
The
RTCRtpSender
instance
attribute EventHandler ontonechange
The
ontonechange
event handler uses the
RTCDTMFToneChangeEvent
interface to return the
character for each tone as it is played out.
readonly attribute DOMString toneBuffer
The
toneBuffer
attribute returns a list of the
tones remaining to be played out.
readonly attribute long duration
The
duration
attribute returns the current tone duration
value in milliseconds. This value will be the value last set via the
insertDTMF()
method, or the default value of 70 ms if
insertDTMF()
was called without specifying the duration.
readonly attribute long interToneGap
The
interToneGap
attribute returns the current value of
the between-tone gap. This value will be the value last set via the
insertDTMF()
method, or the default value of 70
ms if
insertDTMF()
was called without specifying
the interToneGap.
RTCDTMFToneChangeEvent
The tonechange event uses the
RTCDTMFToneChangeEvent
interface.
Firing an tonechange event named
with a DOMString
tone
means
that an event with the name
, which does not bubble (except
where otherwise stated) and is not cancelable (except where otherwise
stated), and which uses the
RTCDTMFToneChangeEvent
interface with the
tone
attribute set to
tone
, MUST be created and dispatched at the given target.
Constructor(DOMString type, RTCDTMFToneChangeEventInit
eventInitDict)
readonly attribute DOMString tone
The
tone
attribute contains the character for the tone that has just begun
playout (see
insertDTMF()
). If the value is the
empty string, it indicates that the previous tone has completed
playback.
DOMString tone
The
tone
parameter is treated as a series of characters.
The characters 0 through 9, A through D, #, and * generate the associated DTMF tones.
The characters a to d are equivalent to A to D.
The character ',' indicates a delay of 2 seconds before processing the next character in the tones parameter.
Unrecognized characters are ignored.
The RTCDataChannel Object
Overview
This section needs reworking. An
RTCDataChannel
class instance allows sending data messages to/from the remote peer.
Interface Definition
readonly attribute RTCDtlsTransport transport
The readonly value referring to the related transport object.
readonly attribute DOMString id
An identifier for the data channel.
readonly attribute DOMString type
The type of data channel being used.
void send(Object data)
Method used for sending data to the remote peer.
Parameter
Type
Nullable
Optional
Description
data
Object
no
no
attribute EventHandler ondata
This event handler, of event handler event type
data
, must be fired to allow a developer's JavaScript to receive data from a remote peer.
Event Argument
Description
Object data
The received remote data.
The RTCSctpTransport Object
The
RTCSctpTransport
includes information relating to Stream Control Transmission Protocol (SCTP) transport.
Overview
An
RTCSctpTransport
is associated to a
RTCDataChannel
Operation
An
RTCSctpTransport
instance is constructed from an
RTCDtlsTransport
object.
Interface Definition
attribute
RTCDtlsTransport
transport
The RTCDtlsTransport instance the RTCSctpTransport object is sending over.
static
RTCSctpCapabilities
getCapabilities()
Retrieves the RTCSctpCapabilities of the RTCSctpTransport instance.
void start(
RTCSctpCapabilities
remoteCaps)
void stop()
Stops the RTCSctpTransport instance.
DataChannel
createDataChannel(
RTCDataChannelParameters
parameters)
Creates a data channel running over SCTP transport.
attribute EventHandler ondatachannel
dictionary RTCDataChannelParameters
boolean outOfOrderAllowed
unsigned short maxRetransmitTime
unsigned short maxRetransmitNum
DOMString protocol
boolean preset
unsigned short stream
dictionary RTCSctpCapabilities
unsigned int maxMessageSize
Example
function initiate(signaller) {
var dtls = ...; // See ICE/DTLS example.
var sctp = new RTCSctpTransport(dtls);
signaller.sendInitiate({
// ... include ICE/DTLS info from other example.
sctpCapabilities: RTCSctpTransport.getCapabilities()
}, function(remote) {
sctp.start(remote.sctpCapabilities);
});
var channel = sctp.createDataChannel({...});
channel.send("foo");
function accept(signaller, remote) {
var dtls = ...; // See ICE/DTLS example.
signaller.sendAccept({
// ... include ICE/DTLS info from other example.
"sctpCapabilities": RTCSctpTransport.getCapabilities()
});
var sctp = new RTCSctpTransport(dtls);
sctp.start(remote.sctpCapabilties);
// Assume in-band signalling. We could also easily add
// RTCDataChannelParameters into the out-of-band signalling
// And call .createDataChannel here with negotiated: true.
sctp.ondatachannel = function(channel) {
channel.onmessage = function(message) {
if (message == "foo") {
channel.send("bar");
RTCP Protocol
This specification determines that RTCP packets must be multiplexed with the RTP packets as defined by [[!RFC5761]].
Examples
Simple Peer-to-peer Example
This example code provides a basic audio and video session between two browsers.
Change Log
This section will be removed before publication.
Changes since 07 November 2013
RTCTrack split into RTCRtpSender and RTCRtpReceiver objects, as proposed on
06 January 2014.
RTCConnection split into RTCIceTransport and RTCDtlsTransport objects, as proposed on
09 January 2014.
RTCSctpTransport object added, as described in
Issue 25
RTCRtpHeaderExtensionParameters added, as described in
Issue 28
RTCIceListener added, in order to support parallel forking, as described in
Issue 29
DTMF support added, as described in
Issue 30